src/小米便签代码注释/BackupUtils.java

src/小米便签代码注释/DataUtils.java
src/小米便签代码注释/GTaskASyncTask.java
src/小米便签代码注释/GTaskManager.java

src/小米便签代码注释/BackupUtils.java

@@ -0,0 +1,356 @@
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.micode.notes.tool;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.os.Environment;
+import android.text.TextUtils;
+import android.text.format.DateFormat;
+import android.util.Log;
+
+import net.micode.notes.R;
+import net.micode.notes.data.Notes;
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.DataConstants;
+import net.micode.notes.data.Notes.NoteColumns;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+
+
+public class BackupUtils {
+    private static final String TAG = "BackupUtils";
+    //    定义了一个 TAG 常量用于日志输出。
+    // Singleton stuff
+    private static BackupUtils sInstance;
+//  然后，定义了一个静态的 sInstance 变量，表示类的唯一实例，
+//  在 getInstance() 方法中进行初始化。getInstance() 方法接收一个 Context 对象，
+//  并通过判断 sInstance 是否为空来决定是否需要创建一个新的 BackupUtils 实例。
+    public static synchronized BackupUtils getInstance(Context context) {
+        if (sInstance == null) {
+            sInstance = new BackupUtils(context);
+        }
+        return sInstance;
+    }
+
+    /**
+     * Following states are signs to represents backup or restore
+     * status
+     */
+    // Currently, the sdcard is not mounted
+    public static final int STATE_SD_CARD_UNMOUONTED           = 0;
+    // The backup file not exist
+    public static final int STATE_BACKUP_FILE_NOT_EXIST        = 1;
+    // The data is not well formated, may be changed by other programs
+    public static final int STATE_DATA_DESTROIED               = 2;
+    // Some run-time exception which causes restore or backup fails
+    public static final int STATE_SYSTEM_ERROR                 = 3;
+    // Backup or restore success
+    public static final int STATE_SUCCESS                      = 4;
+
+    private TextExport mTextExport;
+    //TextExport 对象用于导出文本格式的数据
+    private BackupUtils(Context context) {
+        mTextExport = new TextExport(context);
+    }
+
+    private static boolean externalStorageAvailable() {
+        return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());
+    }
+    //用于检查 SD 卡是否可用，如果当前 SD 卡挂载，则返回 true，否则返回 false。
+    public int exportToText() {
+        return mTextExport.exportToText();
+    }
+    //返回输出文本的文件名
+    public String getExportedTextFileName() {
+        return mTextExport.mFileName;
+    }
+    //返回输出文本文件的路径
+    public String getExportedTextFileDir() {
+        return mTextExport.mFileDirectory;
+    }
+
+    private static class TextExport {
+        //定义了一个数组储存便签的信息
+        private static final String[] NOTE_PROJECTION = {
+                NoteColumns.ID,
+                NoteColumns.MODIFIED_DATE,
+                NoteColumns.SNIPPET,
+                NoteColumns.TYPE
+        };
+
+        private static final int NOTE_COLUMN_ID = 0;
+
+        private static final int NOTE_COLUMN_MODIFIED_DATE = 1;
+
+        private static final int NOTE_COLUMN_SNIPPET = 2;
+
+        private static final String[] DATA_PROJECTION = {
+                DataColumns.CONTENT,
+                DataColumns.MIME_TYPE,
+                DataColumns.DATA1,
+                DataColumns.DATA2,
+                DataColumns.DATA3,
+                DataColumns.DATA4,
+        };
+
+        private static final int DATA_COLUMN_CONTENT = 0;
+
+        private static final int DATA_COLUMN_MIME_TYPE = 1;
+
+        private static final int DATA_COLUMN_CALL_DATE = 2;
+
+        private static final int DATA_COLUMN_PHONE_NUMBER = 4;
+
+        private final String [] TEXT_FORMAT;
+        private static final int FORMAT_FOLDER_NAME          = 0;
+        private static final int FORMAT_NOTE_DATE            = 1;
+        private static final int FORMAT_NOTE_CONTENT         = 2;
+
+        private Context mContext;
+        private String mFileName;
+        private String mFileDirectory;
+
+        //从context类实例中获取信息，给对应的属性赋初始值
+        public TextExport(Context context) {
+            TEXT_FORMAT = context.getResources().getStringArray(R.array.format_for_exported_note);
+            mContext = context;
+            mFileName = "";
+            mFileDirectory = "";
+        }
+        //获取文本组成部分
+        //通过ID返回文件的格式信息
+        private String getFormat(int id) {
+            return TEXT_FORMAT[id];
+        }
+
+        /**
+         * Export the folder identified by folder id to text
+         */
+        //通过查询parent id是文件夹id的note来选出制定ID文件夹下的Note,通过文件夹ID将目录导出后成文件,输出文件夹至文本
+        private void exportFolderToText(String folderId, PrintStream ps) {
+            // Query notes belong to this folder
+            Cursor notesCursor = mContext.getContentResolver().query(Notes.CONTENT_NOTE_URI,
+                    NOTE_PROJECTION, NoteColumns.PARENT_ID + "=?", new String[] {
+                        folderId
+                    }, null);
+
+            if (notesCursor != null) {
+                if (notesCursor.moveToFirst()) {
+                    do {
+                        // Print note's last modified date
+                        ps.println(String.format(getFormat(FORMAT_NOTE_DATE), DateFormat.format(
+                                mContext.getString(R.string.format_datetime_mdhm),
+                                notesCursor.getLong(NOTE_COLUMN_MODIFIED_DATE))));
+                        // Query data belong to this note
+                        String noteId = notesCursor.getString(NOTE_COLUMN_ID);
+                        exportNoteToText(noteId, ps);
+                    } while (notesCursor.moveToNext());
+                }
+                notesCursor.close();
+            }
+        }
+
+        /**
+         * Export note identified by id to a print stream
+         */
+        //将便签的内容以文本的形式显示在屏幕上。比如电话号码、打电话的日期等。
+        private void exportNoteToText(String noteId, PrintStream ps) {
+            Cursor dataCursor = mContext.getContentResolver().query(Notes.CONTENT_DATA_URI,
+                    DATA_PROJECTION, DataColumns.NOTE_ID + "=?", new String[] {
+                        noteId
+                    }, null);
+
+            if (dataCursor != null) {
+                if (dataCursor.moveToFirst()) {
+                    do {
+                        String mimeType = dataCursor.getString(DATA_COLUMN_MIME_TYPE);
+                        if (DataConstants.CALL_NOTE.equals(mimeType)) {
+                            // Print phone number
+                            String phoneNumber = dataCursor.getString(DATA_COLUMN_PHONE_NUMBER);
+                            long callDate = dataCursor.getLong(DATA_COLUMN_CALL_DATE);
+                            String location = dataCursor.getString(DATA_COLUMN_CONTENT);
+
+                            if (!TextUtils.isEmpty(phoneNumber)) {
+                                ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT),
+                                        phoneNumber));
+                            }
+                            // Print call date
+                            ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT), DateFormat
+                                    .format(mContext.getString(R.string.format_datetime_mdhm),
+                                            callDate)));
+                            // Print call attachment location
+                            if (!TextUtils.isEmpty(location)) {
+                                ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT),
+                                        location));
+                            }
+                        } else if (DataConstants.NOTE.equals(mimeType)) {
+                            String content = dataCursor.getString(DATA_COLUMN_CONTENT);
+                            if (!TextUtils.isEmpty(content)) {
+                                ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT),
+                                        content));
+                            }
+                        }
+                    } while (dataCursor.moveToNext());
+                }
+                dataCursor.close();
+            }
+            // print a line separator between note
+            try {
+                ps.write(new byte[] {
+                        Character.LINE_SEPARATOR, Character.LETTER_NUMBER
+                });
+            } catch (IOException e) {
+                Log.e(TAG, e.toString());
+            }
+        }
+
+        /**
+         * Note will be exported as text which is user readable
+         */
+        //以TEXT形式输出到外部设备
+        public int exportToText() {
+            if (!externalStorageAvailable()) {
+                Log.d(TAG, "Media was not mounted");
+                return STATE_SD_CARD_UNMOUONTED;
+            }
+
+            PrintStream ps = getExportToTextPrintStream();
+            if (ps == null) {
+                Log.e(TAG, "get print stream error");
+                return STATE_SYSTEM_ERROR;
+            }
+            // First export folder and its notes
+            Cursor folderCursor = mContext.getContentResolver().query(
+                    Notes.CONTENT_NOTE_URI,
+                    NOTE_PROJECTION,
+                    "(" + NoteColumns.TYPE + "=" + Notes.TYPE_FOLDER + " AND "
+                            + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER + ") OR "
+                            + NoteColumns.ID + "=" + Notes.ID_CALL_RECORD_FOLDER, null, null);
+
+            if (folderCursor != null) {
+                if (folderCursor.moveToFirst()) {
+                    do {
+                        // Print folder's name
+                        String folderName = "";
+                        if(folderCursor.getLong(NOTE_COLUMN_ID) == Notes.ID_CALL_RECORD_FOLDER) {
+                            folderName = mContext.getString(R.string.call_record_folder_name);
+                        } else {
+                            folderName = folderCursor.getString(NOTE_COLUMN_SNIPPET);
+                        }
+                        if (!TextUtils.isEmpty(folderName)) {
+                            ps.println(String.format(getFormat(FORMAT_FOLDER_NAME), folderName));
+                        }
+                        String folderId = folderCursor.getString(NOTE_COLUMN_ID);
+                        exportFolderToText(folderId, ps);
+                    } while (folderCursor.moveToNext());
+                }
+                folderCursor.close();
+            }
+
+            // Export notes in root's folder
+            Cursor noteCursor = mContext.getContentResolver().query(
+                    Notes.CONTENT_NOTE_URI,
+                    NOTE_PROJECTION,
+                    NoteColumns.TYPE + "=" + +Notes.TYPE_NOTE + " AND " + NoteColumns.PARENT_ID
+                            + "=0", null, null);
+
+            if (noteCursor != null) {
+                if (noteCursor.moveToFirst()) {
+                    do {
+                        ps.println(String.format(getFormat(FORMAT_NOTE_DATE), DateFormat.format(
+                                mContext.getString(R.string.format_datetime_mdhm),
+                                noteCursor.getLong(NOTE_COLUMN_MODIFIED_DATE))));
+                        // Query data belong to this note
+                        String noteId = noteCursor.getString(NOTE_COLUMN_ID);
+                        exportNoteToText(noteId, ps);
+                    } while (noteCursor.moveToNext());
+                }
+                noteCursor.close();
+            }
+            ps.close();
+
+            return STATE_SUCCESS;
+        }
+
+        /**
+         * Get a print stream pointed to the file {@generateExportedTextFile}
+         */
+        //获取指向文件的打印流
+        //将要输出的内容整合到一个输出里并返回该输出流
+        private PrintStream getExportToTextPrintStream() {
+            File file = generateFileMountedOnSDcard(mContext, R.string.file_path,
+                    R.string.file_name_txt_format);
+            if (file == null) {
+                Log.e(TAG, "create file to exported failed");
+                return null;
+            }
+            mFileName = file.getName();
+            mFileDirectory = mContext.getString(R.string.file_path);
+            PrintStream ps = null;
+            try {
+                FileOutputStream fos = new FileOutputStream(file);
+                ps = new PrintStream(fos);
+            } catch (FileNotFoundException e) {
+                e.printStackTrace();
+                return null;
+            } catch (NullPointerException e) {
+                e.printStackTrace();
+                return null;
+            }
+            return ps;
+        }
+    }
+
+    /**
+     * Generate the text file to store imported data
+     */
+    //产生用于存储输入信息的文件,使文本文件存储重要数据
+    private static File generateFileMountedOnSDcard(Context context, int filePathResId, int fileNameFormatResId) {
+        StringBuilder sb = new StringBuilder();
+        sb.append(Environment.getExternalStorageDirectory());
+        sb.append(context.getString(filePathResId));
+        File filedir = new File(sb.toString());
+        sb.append(context.getString(
+                fileNameFormatResId,
+                DateFormat.format(context.getString(R.string.format_date_ymd),
+                        System.currentTimeMillis())));
+        File file = new File(sb.toString());
+
+        try {
+            if (!filedir.exists()) {
+                filedir.mkdir();
+            }
+            if (!file.exists()) {
+                file.createNewFile();
+            }
+            return file;
+        } catch (SecurityException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+}
+
+

src/小米便签代码注释/DataUtils.java

@@ -0,0 +1,297 @@
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.micode.notes.tool;
+
+import android.content.ContentProviderOperation;
+import android.content.ContentProviderResult;
+import android.content.ContentResolver;
+import android.content.ContentUris;
+import android.content.ContentValues;
+import android.content.OperationApplicationException;
+import android.database.Cursor;
+import android.os.RemoteException;
+import android.util.Log;
+
+import net.micode.notes.data.Notes;
+import net.micode.notes.data.Notes.CallNote;
+import net.micode.notes.data.Notes.NoteColumns;
+import net.micode.notes.ui.NotesListAdapter.AppWidgetAttribute;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+
+
+public class DataUtils {
+    public static final String TAG = "DataUtils";
+    //直接删除多个笔记
+    public static boolean batchDeleteNotes(ContentResolver resolver, HashSet<Long> ids) {
+        if (ids == null) {
+            Log.d(TAG, "the ids is null");
+            return true;
+        }
+        if (ids.size() == 0) {
+            Log.d(TAG, "no id is in the hashset");
+            return true;
+        }
+        //提供一个任务列表
+        ArrayList<ContentProviderOperation> operationList = new ArrayList<ContentProviderOperation>();
+        for (long id : ids) {
+            if(id == Notes.ID_ROOT_FOLDER) {
+                Log.e(TAG, "Don't delete system folder root");
+                continue;
+            }//如果发现是根文件夹，则不删除
+            ContentProviderOperation.Builder builder = ContentProviderOperation//用newDelete实现删除功能
+                    .newDelete(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, id));
+            operationList.add(builder.build());
+        }
+        try {
+            ContentProviderResult[] results = resolver.applyBatch(Notes.AUTHORITY, operationList);
+            //数据库事务，数据库事务是由一组数据库操作序列组成，事务作为一个整体被执行
+            if (results == null || results.length == 0 || results[0] == null) {
+                Log.d(TAG, "delete notes failed, ids:" + ids.toString());
+                return false;
+            }
+            return true;
+        } catch (RemoteException e) {
+            Log.e(TAG, String.format("%s: %s", e.toString(), e.getMessage()));
+        } catch (OperationApplicationException e) {
+            Log.e(TAG, String.format("%s: %s", e.toString(), e.getMessage()));
+        }
+        return false;
+    }
+
+    public static void moveNoteToFoler(ContentResolver resolver, long id, long srcFolderId, long desFolderId) {
+        ContentValues values = new ContentValues();
+        values.put(NoteColumns.PARENT_ID, desFolderId);
+        values.put(NoteColumns.ORIGIN_PARENT_ID, srcFolderId);
+        values.put(NoteColumns.LOCAL_MODIFIED, 1);
+        resolver.update(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, id), values, null, null); //对需要移动的便签进行数据更新，然后用update实现
+    }
+
+    public static boolean batchMoveToFolder(ContentResolver resolver, HashSet<Long> ids,
+            long folderId) {
+        if (ids == null) {
+            Log.d(TAG, "the ids is null");
+            return true;
+        }
+
+        ArrayList<ContentProviderOperation> operationList = new ArrayList<ContentProviderOperation>();
+        for (long id : ids) {
+            ContentProviderOperation.Builder builder = ContentProviderOperation
+                    .newUpdate(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, id));
+            builder.withValue(NoteColumns.PARENT_ID, folderId);
+            builder.withValue(NoteColumns.LOCAL_MODIFIED, 1);
+            operationList.add(builder.build());
+        }//将ids里包含的每一列的数据逐次加入到operationList中，等待最后的批量处理
+
+        try {
+            ContentProviderResult[] results = resolver.applyBatch(Notes.AUTHORITY, operationList);
+            if (results == null || results.length == 0 || results[0] == null) {
+                Log.d(TAG, "delete notes failed, ids:" + ids.toString());
+                return false;
+            }
+            return true;
+        } catch (RemoteException e) {
+            Log.e(TAG, String.format("%s: %s", e.toString(), e.getMessage()));
+        } catch (OperationApplicationException e) {
+            Log.e(TAG, String.format("%s: %s", e.toString(), e.getMessage()));
+        }
+        return false;
+    }
+
+    /**
+     * Get the all folder count except system folders {@link Notes#TYPE_SYSTEM}}
+     */
+    public static int getUserFolderCount(ContentResolver resolver) {
+        Cursor cursor =resolver.query(Notes.CONTENT_NOTE_URI,
+                new String[] { "COUNT(*)" },
+                NoteColumns.TYPE + "=? AND " + NoteColumns.PARENT_ID + "<>?",
+                new String[] { String.valueOf(Notes.TYPE_FOLDER), String.valueOf(Notes.ID_TRASH_FOLER)},
+                null); //筛选条件：源文件不为trash folder
+
+        int count = 0;
+        if(cursor != null) {
+            if(cursor.moveToFirst()) {
+                try {
+                    count = cursor.getInt(0);
+                } catch (IndexOutOfBoundsException e) {
+                    Log.e(TAG, "get folder count failed:" + e.toString());
+                } finally {
+                    cursor.close();
+                }
+            }
+        }
+        return count;
+    }
+
+    public static boolean visibleInNoteDatabase(ContentResolver resolver, long noteId, int type) {
+        Cursor cursor = resolver.query(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId),
+                null,
+                NoteColumns.TYPE + "=? AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER,
+                new String [] {String.valueOf(type)},
+                null);//查询条件：type符合，且不属于垃圾文件夹
+
+        boolean exist = false;
+        if (cursor != null) {
+            if (cursor.getCount() > 0) {
+                exist = true;
+            }
+            cursor.close();
+        }
+        return exist;
+    }
+
+    public static boolean existInNoteDatabase(ContentResolver resolver, long noteId) {
+        Cursor cursor = resolver.query(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId),
+                null, null, null, null);
+
+        boolean exist = false;
+        if (cursor != null) {
+            if (cursor.getCount() > 0) {
+                exist = true;
+            }
+            cursor.close();
+        }
+        return exist;
+    }
+
+    public static boolean existInDataDatabase(ContentResolver resolver, long dataId) {
+        Cursor cursor = resolver.query(ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId),
+                null, null, null, null);
+
+        boolean exist = false;
+        if (cursor != null) {
+            if (cursor.getCount() > 0) {
+                exist = true;
+            }
+            cursor.close();
+        }
+        return exist;
+    }
+
+    public static boolean checkVisibleFolderName(ContentResolver resolver, String name) {
+        Cursor cursor = resolver.query(Notes.CONTENT_NOTE_URI, null,
+                NoteColumns.TYPE + "=" + Notes.TYPE_FOLDER +
+                " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER +
+                " AND " + NoteColumns.SNIPPET + "=?",
+                new String[] { name }, null);
+        boolean exist = false;
+        if(cursor != null) {
+            if(cursor.getCount() > 0) {
+                exist = true;
+            }
+            cursor.close();
+        }
+        return exist;
+    }
+
+    public static HashSet<AppWidgetAttribute> getFolderNoteWidget(ContentResolver resolver, long folderId) {
+        Cursor c = resolver.query(Notes.CONTENT_NOTE_URI,
+                new String[] { NoteColumns.WIDGET_ID, NoteColumns.WIDGET_TYPE },
+                NoteColumns.PARENT_ID + "=?",
+                new String[] { String.valueOf(folderId) },
+                null);
+        //通过数据库操作，查询条件是（callDate和phoneNumber匹配传入参数的值）
+        HashSet<AppWidgetAttribute> set = null;
+        if (c != null) {
+            if (c.moveToFirst()) {
+                set = new HashSet<AppWidgetAttribute>();
+                do {
+                    try {
+                        AppWidgetAttribute widget = new AppWidgetAttribute();
+                        widget.widgetId = c.getInt(0);
+                        widget.widgetType = c.getInt(1);
+                        set.add(widget);
+                    } catch (IndexOutOfBoundsException e) {
+                        Log.e(TAG, e.toString());
+                    }
+                } while (c.moveToNext());
+            }
+            c.close();
+        }
+        return set;
+    }
+
+    public static String getCallNumberByNoteId(ContentResolver resolver, long noteId) {
+        Cursor cursor = resolver.query(Notes.CONTENT_DATA_URI,
+                new String [] { CallNote.PHONE_NUMBER },
+                CallNote.NOTE_ID + "=? AND " + CallNote.MIME_TYPE + "=?",
+                new String [] { String.valueOf(noteId), CallNote.CONTENT_ITEM_TYPE },//查询条件：noteId
+                null);
+
+        if (cursor != null && cursor.moveToFirst()) {
+            try {
+                return cursor.getString(0);
+            } catch (IndexOutOfBoundsException e) {
+                Log.e(TAG, "Get call number fails " + e.toString());
+            } finally {
+                cursor.close();
+            }
+        }
+        return "";
+    }
+
+    public static long getNoteIdByPhoneNumberAndCallDate(ContentResolver resolver, String phoneNumber, long callDate) {
+        Cursor cursor = resolver.query(Notes.CONTENT_DATA_URI,
+                new String [] { CallNote.NOTE_ID },
+                CallNote.CALL_DATE + "=? AND " + CallNote.MIME_TYPE + "=? AND PHONE_NUMBERS_EQUAL("
+                + CallNote.PHONE_NUMBER + ",?)",
+                new String [] { String.valueOf(callDate), CallNote.CONTENT_ITEM_TYPE, phoneNumber },
+                null);
+
+        if (cursor != null) {
+            if (cursor.moveToFirst()) {
+                try {
+                    return cursor.getLong(0);
+                } catch (IndexOutOfBoundsException e) {
+                    Log.e(TAG, "Get call note id fails " + e.toString());
+                }
+            }
+            cursor.close();
+        }
+        return 0;
+    }
+
+    public static String getSnippetById(ContentResolver resolver, long noteId) {
+        Cursor cursor = resolver.query(Notes.CONTENT_NOTE_URI,
+                new String [] { NoteColumns.SNIPPET },
+                NoteColumns.ID + "=?",
+                new String [] { String.valueOf(noteId)},
+                null);
+
+        if (cursor != null) {
+            String snippet = "";
+            if (cursor.moveToFirst()) {
+                snippet = cursor.getString(0);
+            }
+            cursor.close();
+            return snippet;
+        }
+        throw new IllegalArgumentException("Note is not found with id: " + noteId);
+    }
+
+    public static String getFormattedSnippet(String snippet) {//对字符串进行格式处理，将字符串两头的空格去掉，同时将换行符去掉
+        if (snippet != null) {
+            snippet = snippet.trim();
+            int index = snippet.indexOf('\n');
+            if (index != -1) {
+                snippet = snippet.substring(0, index);
+            }
+        }
+        return snippet;
+    }
+}

src/小米便签代码注释/GTaskASyncTask.java

@@ -0,0 +1,129 @@
+
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.micode.notes.gtask.remote;
+
+import android.app.Notification;
+import android.app.NotificationManager;
+import android.app.PendingIntent;
+import android.content.Context;
+import android.content.Intent;
+import android.os.AsyncTask;
+
+import net.micode.notes.R;
+import net.micode.notes.ui.NotesListActivity;
+import net.micode.notes.ui.NotesPreferenceActivity;
+
+
+public class GTaskASyncTask extends AsyncTask<Void, String, Integer> {
+    //异步操作类，实现GTask的异步操作过程
+    private static int GTASK_SYNC_NOTIFICATION_ID = 5234235;
+
+    public interface OnCompleteListener {
+        void onComplete();
+    }
+
+    private Context mContext;
+
+    private NotificationManager mNotifiManager;
+
+    private GTaskManager mTaskManager;
+
+    private OnCompleteListener mOnCompleteListener;
+
+    public GTaskASyncTask(Context context, OnCompleteListener listener) {
+        mContext = context;
+        mOnCompleteListener = listener;
+        mNotifiManager = (NotificationManager) mContext
+                .getSystemService(Context.NOTIFICATION_SERVICE);
+        mTaskManager = GTaskManager.getInstance();
+    }
+
+    public void cancelSync() {
+        mTaskManager.cancelSync();
+    }
+
+    public void publishProgess(String message) {
+        publishProgress(new String[] {
+            message
+        });
+    }
+
+    private void showNotification(int tickerId, String content) {// 向用户提示当前同步的状态，是一个用于交互的方法
+        PendingIntent pendingIntent;
+        if (tickerId != R.string.ticker_success) {
+            pendingIntent = PendingIntent.getActivity(mContext, 0, new Intent(mContext,
+                    NotesPreferenceActivity.class), 0);
+
+        } else {
+            pendingIntent = PendingIntent.getActivity(mContext, 0, new Intent(mContext,
+                    NotesListActivity.class), 0);
+        }
+
+
+        Notification.Builder builder = new Notification.Builder(mContext)
+                .setAutoCancel(true)
+                .setContentTitle(mContext.getString(R.string.app_name))
+                .setContentText(content)
+                .setContentIntent(pendingIntent)
+                .setWhen(System.currentTimeMillis())
+                .setOngoing(true);
+        Notification notification=builder.getNotification();
+        mNotifiManager.notify(GTASK_SYNC_NOTIFICATION_ID, notification);
+    }
+
+
+
+    @Override
+    protected Integer doInBackground(Void... unused) {//此方法在后台线程执行，完成任务的主要工作，通常需要较长的时间
+        publishProgess(mContext.getString(R.string.sync_progress_login, NotesPreferenceActivity
+                .getSyncAccountName(mContext)));
+        return mTaskManager.sync(mContext, this);
+    }
+
+    @Override
+    protected void onProgressUpdate(String... progress) {//可以使用进度条增加用户体验度。 此方法在主线程执行，用于显示任务执行的进度。
+        showNotification(R.string.ticker_syncing, progress[0]);
+        if (mContext instanceof GTaskSyncService) {
+            ((GTaskSyncService) mContext).sendBroadcast(progress[0]);
+        }
+    }
+
+    @Override
+    protected void onPostExecute(Integer result) {//相当于Handler 处理UI的方式，在这里面可以使用在doInBackground 得到的结果处理操作UI
+        if (result == GTaskManager.STATE_SUCCESS) {
+            showNotification(R.string.ticker_success, mContext.getString(
+                    R.string.success_sync_account, mTaskManager.getSyncAccount()));
+            NotesPreferenceActivity.setLastSyncTime(mContext, System.currentTimeMillis());
+        } else if (result == GTaskManager.STATE_NETWORK_ERROR) {
+            showNotification(R.string.ticker_fail, mContext.getString(R.string.error_sync_network));
+        } else if (result == GTaskManager.STATE_INTERNAL_ERROR) {
+            showNotification(R.string.ticker_fail, mContext.getString(R.string.error_sync_internal));
+        } else if (result == GTaskManager.STATE_SYNC_CANCELLED) {
+            showNotification(R.string.ticker_cancel, mContext
+                    .getString(R.string.error_sync_cancelled));
+        }
+        if (mOnCompleteListener != null) {
+            new Thread(new Runnable() {
+
+                public void run() {
+                    mOnCompleteListener.onComplete();
+                }
+            }).start();
+        }
+    }
+}

src/小米便签代码注释/GTaskManager.java

@@ -0,0 +1,846 @@
+package net.micode.notes.gtask.remote;
+
+public class GTaskManager {
+    private static final String TAG = GTaskManager.class.getSimpleName();
+    public static final int STATE_SUCCESS = 0;
+    public static final int STATE_NETWORK_ERROR = 1;
+    public static final int STATE_INTERNAL_ERROR = 2;
+    public static final int STATE_SYNC_IN_PROGRESS = 3;
+    public static final int STATE_SYNC_CANCELLED = 4;
+    private static GTaskManager mInstance = null;
+
+    private Activity mActivity;
+    private Context mContext;
+    private ContentResolver mContentResolver;
+    private boolean mSyncing;
+    private boolean mCancelled;
+    private HashMap<String, TaskList> mGTaskListHashMap;
+    private HashMap<String, Node> mGTaskHashMap;
+    private HashMap<String, MetaData> mMetaHashMap;
+    private TaskList mMetaList;
+    private HashSet<Long> mLocalDeleteIdMap;
+    private HashMap<String, Long> mGidToNid;
+    private HashMap<Long, String> mNidToGid;
+
+    private GTaskManager() {                                   //对象初始化函数
+        mSyncing = false;                                      //正在同步,flase代表未执行
+        mCancelled = false;                                    //全局标识，flase代表可以执行
+        mGTaskListHashMap = new HashMap<String, TaskList>();   //<>代表Java的泛型,就是创建一个用类型作为参数的类。
+        mGTaskHashMap = new HashMap<String, Node>();
+        mMetaHashMap = new HashMap<String, MetaData>();
+        mMetaList = null;
+        mLocalDeleteIdMap = new HashSet<Long>();
+        mGidToNid = new HashMap<String, Long>();    //GoogleID to NodeID??
+        mNidToGid = new HashMap<Long, String>();    //NodeID to GoogleID???通过hashmap散列表建立映射
+    }
+
+    /**
+     * 包含关键字synchronized，语言级同步，指明该函数可能运行在多线程的环境下。
+     * 功能：类初始化函数
+     * @author TTS
+     * @return GtaskManger
+     */
+    public static synchronized GTaskManager getInstance() {    //可能运行在多线程环境下，使用语言级同步--synchronized
+        if (mInstance == null) {
+            mInstance = new GTaskManager();
+        }
+        return mInstance;
+    }
+
+    /**
+     * 包含关键字synchronized，语言级同步，指明该函数可能运行在多线程的环境下。
+     * @author TTS
+     * @param activity
+     */
+    public synchronized void setActivityContext(Activity activity) {
+        // used for getting auth token
+        mActivity = activity;
+    }
+
+    /**
+     * 核心函数
+     * 功能：实现了本地同步操作和远端同步操作
+     * @author TTS
+     * @param context-----获取上下文
+     * @param asyncTask-------用于同步的异步操作类
+     * @return int
+     */
+    public int sync(Context context, GTaskASyncTask asyncTask) {           //核心函数
+        if (mSyncing) {
+            Log.d(TAG, "Sync is in progress");                       //创建日志文件（调试信息），debug
+            return STATE_SYNC_IN_PROGRESS;
+        }
+        mContext = context;
+        mContentResolver = mContext.getContentResolver();
+        mSyncing = true;
+        mCancelled = false;
+        mGTaskListHashMap.clear();
+        mGTaskHashMap.clear();
+        mMetaHashMap.clear();
+        mLocalDeleteIdMap.clear();
+        mGidToNid.clear();
+        mNidToGid.clear();
+
+        try {
+            GTaskClient client = GTaskClient.getInstance();    //getInstance即为创建一个实例,client--客户机
+            client.resetUpdateArray();     //JSONArray类型，reset即置为NULL
+
+            // login google task
+            if (!mCancelled) {
+                if (!client.login(mActivity)) {
+                    throw new NetworkFailureException("login google task failed");
+                }
+            }
+
+            // get the task list from google
+            asyncTask.publishProgess(mContext.getString(R.string.sync_progress_init_list));
+            initGTaskList();                                 //获取Google上的JSONtasklist转为本地TaskList
+
+            // do content sync work
+            asyncTask.publishProgess(mContext.getString(R.string.sync_progress_syncing));
+            syncContent();
+        } catch (NetworkFailureException e) {                       //分为两种异常，此类异常为网络异常
+            Log.e(TAG, e.toString());                             //创建日志文件（调试信息），error
+            return STATE_NETWORK_ERROR;
+        } catch (ActionFailureException e) {                        //此类异常为操作异常
+            Log.e(TAG, e.toString());
+            return STATE_INTERNAL_ERROR;
+        } catch (Exception e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+            return STATE_INTERNAL_ERROR;
+        } finally {
+            mGTaskListHashMap.clear();
+            mGTaskHashMap.clear();
+            mMetaHashMap.clear();
+            mLocalDeleteIdMap.clear();
+            mGidToNid.clear();
+            mNidToGid.clear();
+            mSyncing = false;
+        }
+
+        return mCancelled ? STATE_SYNC_CANCELLED : STATE_SUCCESS;
+    }
+
+    /**
+     *功能：初始化GtaskList，获取Google上的JSONtasklist转为本地TaskList。
+     *获得的数据存储在mMetaList，mGTaskListHashMap，mGTaskHashMap
+     *@author TTS
+     *@exception NetworkFailureException
+     *@return void
+     */
+    private void initGTaskList() throws NetworkFailureException {
+        if (mCancelled)
+            return;
+        GTaskClient client = GTaskClient.getInstance();    //getInstance即为创建一个实例，client应指远端客户机
+        try {
+            //Json对象是Name Value对(即子元素)的无序集合，相当于一个Map对象。JsonObject类是bantouyan-json库对Json对象的抽象，提供操纵Json对象的各种方法。
+            //其格式为{"key1":value1,"key2",value2....};key 必须是字符串。
+            //因为ajax请求不刷新页面，但配合js可以实现局部刷新，因此json常常被用来作为异步请求的返回对象使用。
+            JSONArray jsTaskLists = client.getTaskLists();     //原注释为get task list------lists？？？
+
+            // init meta list first
+            mMetaList = null;                                       //TaskList类型
+            for (int i = 0; i < jsTaskLists.length(); i++) {
+                JSONObject object = jsTaskLists.getJSONObject(i);  //JSONObject与JSONArray一个为对象，一个为数组。此处取出单个JASONObject
+                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
+                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);
+
+                if (name.equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_META)) {
+                    mMetaList = new TaskList();                    //MetaList意为元表,Tasklist类型，此处为初始化
+                    mMetaList.setContentByRemoteJSON(object);      //将JSON中部分数据复制到自己定义的对象中相对应的数据：name->mname...
+
+                    // load meta data
+                    JSONArray jsMetas = client.getTaskList(gid);   //原注释为get action_list------list？？？
+                    for (int j = 0; j < jsMetas.length(); j++) {
+                        object = (JSONObject) jsMetas.getJSONObject(j);
+                        MetaData metaData = new MetaData();            //继承自Node
+                        metaData.setContentByRemoteJSON(object);
+                        if (metaData.isWorthSaving()) {                             //if not worth to save，metadata将不加入mMetaList
+                            mMetaList.addChildTask(metaData);
+                            if (metaData.getGid() != null) {
+                                mMetaHashMap.put(metaData.getRelatedGid(), metaData);
+                            }
+                        }
+                    }
+                }
+            }
+
+            // create meta list if not existed
+            if (mMetaList == null) {
+                mMetaList = new TaskList();
+                mMetaList.setName(GTaskStringUtils.MIUI_FOLDER_PREFFIX
+                        + GTaskStringUtils.FOLDER_META);
+                GTaskClient.getInstance().createTaskList(mMetaList);
+            }
+
+            // init task list
+            for (int i = 0; i < jsTaskLists.length(); i++) {
+                JSONObject object = jsTaskLists.getJSONObject(i);
+                String gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);  //通过getString函数传入本地某个标志数据的名称，获取其在远端的名称。
+                String name = object.getString(GTaskStringUtils.GTASK_JSON_NAME);
+
+                if (name.startsWith(GTaskStringUtils.MIUI_FOLDER_PREFFIX)
+                        && !name.equals(GTaskStringUtils.MIUI_FOLDER_PREFFIX
+                        + GTaskStringUtils.FOLDER_META)) {
+                    TaskList tasklist = new TaskList();     //继承自Node
+                    tasklist.setContentByRemoteJSON(object);
+                    mGTaskListHashMap.put(gid, tasklist);
+                    mGTaskHashMap.put(gid, tasklist);          //为什么加两遍？？？
+
+                    // load tasks
+                    JSONArray jsTasks = client.getTaskList(gid);
+                    for (int j = 0; j < jsTasks.length(); j++) {
+                        object = (JSONObject) jsTasks.getJSONObject(j);
+                        gid = object.getString(GTaskStringUtils.GTASK_JSON_ID);
+                        Task task = new Task();
+                        task.setContentByRemoteJSON(object);
+                        if (task.isWorthSaving()) {
+                            task.setMetaInfo(mMetaHashMap.get(gid));
+                            tasklist.addChildTask(task);
+                            mGTaskHashMap.put(gid, task);
+                        }
+                    }
+                }
+            }
+        } catch (JSONException e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+            throw new ActionFailureException("initGTaskList: handing JSONObject failed");
+        }
+    }
+
+    /**
+     * 功能：本地内容同步操作
+     * @throws NetworkFailureException
+     * @return 无返回值
+     */
+    private void syncContent() throws NetworkFailureException {    //本地内容同步操作
+        int syncType;
+        Cursor c = null;                                           //数据库指针
+        String gid;                                                //GoogleID??
+        Node node;                                                 //Node包含Sync_Action的不同类型
+
+        mLocalDeleteIdMap.clear();                                 //HashSet<Long>类型
+
+        if (mCancelled) {
+            return;
+        }
+
+        // for local deleted note
+        try {
+            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
+                    "(type<>? AND parent_id=?)", new String[] {
+                            String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)
+                    }, null);
+            if (c != null) {
+                while (c.moveToNext()) {
+                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                    node = mGTaskHashMap.get(gid);
+                    if (node != null) {
+                        mGTaskHashMap.remove(gid);
+                        doContentSync(Node.SYNC_ACTION_DEL_REMOTE, node, c);
+                    }
+
+                    mLocalDeleteIdMap.add(c.getLong(SqlNote.ID_COLUMN));
+                }
+            } else {
+                Log.w(TAG, "failed to query trash folder");
+            }
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+
+        // sync folder first
+        syncFolder();
+
+        // for note existing in database
+        try {
+            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
+                    "(type=? AND parent_id<>?)", new String[] {
+                            String.valueOf(Notes.TYPE_NOTE), String.valueOf(Notes.ID_TRASH_FOLER)
+                    }, NoteColumns.TYPE + " DESC");
+            if (c != null) {
+                while (c.moveToNext()) {
+                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                    node = mGTaskHashMap.get(gid);
+                    if (node != null) {
+                        mGTaskHashMap.remove(gid);
+                        mGidToNid.put(gid, c.getLong(SqlNote.ID_COLUMN));   //通过hashmap建立联系
+                        mNidToGid.put(c.getLong(SqlNote.ID_COLUMN), gid);   //通过hashmap建立联系
+                        syncType = node.getSyncAction(c);
+                    } else {
+                        if (c.getString(SqlNote.GTASK_ID_COLUMN).trim().length() == 0) {
+                            // local add
+                            syncType = Node.SYNC_ACTION_ADD_REMOTE;
+                        } else {
+                            // remote delete
+                            syncType = Node.SYNC_ACTION_DEL_LOCAL;
+                        }
+                    }
+                    doContentSync(syncType, node, c);
+                }
+            } else {
+                Log.w(TAG, "failed to query existing note in database");
+            }
+
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+
+        // go through remaining items
+        Iterator<Map.Entry<String, Node>> iter = mGTaskHashMap.entrySet().iterator();   //Iterator迭代器
+        while (iter.hasNext()) {
+            Map.Entry<String, Node> entry = iter.next();
+            node = entry.getValue();
+            doContentSync(Node.SYNC_ACTION_ADD_LOCAL, node, null);
+        }
+
+        // mCancelled can be set by another thread, so we neet to check one by    //thread----线程
+        // one
+        // clear local delete table
+        if (!mCancelled) {
+            if (!DataUtils.batchDeleteNotes(mContentResolver, mLocalDeleteIdMap)) {
+                throw new ActionFailureException("failed to batch-delete local deleted notes");
+            }
+        }
+
+        // refresh local sync id
+        if (!mCancelled) {
+            GTaskClient.getInstance().commitUpdate();
+            refreshLocalSyncId();
+        }
+
+    }
+
+    /**
+     * 功能：
+     * @author TTS
+     * @throws NetworkFailureException
+     */
+    private void syncFolder() throws NetworkFailureException {
+        Cursor c = null;
+        String gid;
+        Node node;
+        int syncType;
+
+        if (mCancelled) {
+            return;
+        }
+
+        // for root folder
+        try {
+            c = mContentResolver.query(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI,
+                    Notes.ID_ROOT_FOLDER), SqlNote.PROJECTION_NOTE, null, null, null);
+            if (c != null) {
+                c.moveToNext();
+                gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                node = mGTaskHashMap.get(gid);
+                if (node != null) {
+                    mGTaskHashMap.remove(gid);
+                    mGidToNid.put(gid, (long) Notes.ID_ROOT_FOLDER);
+                    mNidToGid.put((long) Notes.ID_ROOT_FOLDER, gid);
+                    // for system folder, only update remote name if necessary
+                    if (!node.getName().equals(
+                            GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_DEFAULT))
+                        doContentSync(Node.SYNC_ACTION_UPDATE_REMOTE, node, c);
+                } else {
+                    doContentSync(Node.SYNC_ACTION_ADD_REMOTE, node, c);
+                }
+            } else {
+                Log.w(TAG, "failed to query root folder");
+            }
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+
+        // for call-note folder
+        try {
+            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE, "(_id=?)",
+                    new String[] {
+                            String.valueOf(Notes.ID_CALL_RECORD_FOLDER)
+                    }, null);
+            if (c != null) {
+                if (c.moveToNext()) {
+                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                    node = mGTaskHashMap.get(gid);
+                    if (node != null) {
+                        mGTaskHashMap.remove(gid);
+                        mGidToNid.put(gid, (long) Notes.ID_CALL_RECORD_FOLDER);
+                        mNidToGid.put((long) Notes.ID_CALL_RECORD_FOLDER, gid);
+                        // for system folder, only update remote name if
+                        // necessary
+                        if (!node.getName().equals(
+                                GTaskStringUtils.MIUI_FOLDER_PREFFIX
+                                        + GTaskStringUtils.FOLDER_CALL_NOTE))
+                            doContentSync(Node.SYNC_ACTION_UPDATE_REMOTE, node, c);
+                    } else {
+                        doContentSync(Node.SYNC_ACTION_ADD_REMOTE, node, c);
+                    }
+                }
+            } else {
+                Log.w(TAG, "failed to query call note folder");
+            }
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+
+        // for local existing folders
+        try {
+            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
+                    "(type=? AND parent_id<>?)", new String[] {
+                            String.valueOf(Notes.TYPE_FOLDER), String.valueOf(Notes.ID_TRASH_FOLER)
+                    }, NoteColumns.TYPE + " DESC");
+            if (c != null) {
+                while (c.moveToNext()) {
+                    gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                    node = mGTaskHashMap.get(gid);
+                    if (node != null) {
+                        mGTaskHashMap.remove(gid);
+                        mGidToNid.put(gid, c.getLong(SqlNote.ID_COLUMN));
+                        mNidToGid.put(c.getLong(SqlNote.ID_COLUMN), gid);
+                        syncType = node.getSyncAction(c);
+                    } else {
+                        if (c.getString(SqlNote.GTASK_ID_COLUMN).trim().length() == 0) {
+                            // local add
+                            syncType = Node.SYNC_ACTION_ADD_REMOTE;
+                        } else {
+                            // remote delete
+                            syncType = Node.SYNC_ACTION_DEL_LOCAL;
+                        }
+                    }
+                    doContentSync(syncType, node, c);
+                }
+            } else {
+                Log.w(TAG, "failed to query existing folder");
+            }
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+
+        // for remote add folders
+        Iterator<Map.Entry<String, TaskList>> iter = mGTaskListHashMap.entrySet().iterator();
+        while (iter.hasNext()) {
+            Map.Entry<String, TaskList> entry = iter.next();
+            gid = entry.getKey();
+            node = entry.getValue();
+            if (mGTaskHashMap.containsKey(gid)) {
+                mGTaskHashMap.remove(gid);
+                doContentSync(Node.SYNC_ACTION_ADD_LOCAL, node, null);
+            }
+        }
+
+        if (!mCancelled)
+            GTaskClient.getInstance().commitUpdate();
+    }
+
+    /**
+     * 功能：syncType分类，addLocalNode，addRemoteNode，deleteNode，updateLocalNode，updateRemoteNode
+     * @author TTS
+     * @param syncType
+     * @param node
+     * @param c
+     * @throws NetworkFailureException
+     */
+    private void doContentSync(int syncType, Node node, Cursor c) throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        MetaData meta;
+        switch (syncType) {
+            case Node.SYNC_ACTION_ADD_LOCAL:
+                addLocalNode(node);
+                break;
+            case Node.SYNC_ACTION_ADD_REMOTE:
+                addRemoteNode(node, c);
+                break;
+            case Node.SYNC_ACTION_DEL_LOCAL:
+                meta = mMetaHashMap.get(c.getString(SqlNote.GTASK_ID_COLUMN));
+                if (meta != null) {
+                    GTaskClient.getInstance().deleteNode(meta);
+                }
+                mLocalDeleteIdMap.add(c.getLong(SqlNote.ID_COLUMN));
+                break;
+            case Node.SYNC_ACTION_DEL_REMOTE:
+                meta = mMetaHashMap.get(node.getGid());
+                if (meta != null) {
+                    GTaskClient.getInstance().deleteNode(meta);
+                }
+                GTaskClient.getInstance().deleteNode(node);
+                break;
+            case Node.SYNC_ACTION_UPDATE_LOCAL:
+                updateLocalNode(node, c);
+                break;
+            case Node.SYNC_ACTION_UPDATE_REMOTE:
+                updateRemoteNode(node, c);
+                break;
+            case Node.SYNC_ACTION_UPDATE_CONFLICT:
+                // merging both modifications maybe a good idea
+                // right now just use local update simply
+                updateRemoteNode(node, c);
+                break;
+            case Node.SYNC_ACTION_NONE:
+                break;
+            case Node.SYNC_ACTION_ERROR:
+            default:
+                throw new ActionFailureException("unkown sync action type");
+        }
+    }
+
+    /**
+     * 功能：本地增加Node
+     * @author TTS
+     * @param node
+     * @throws NetworkFailureException
+     */
+    private void addLocalNode(Node node) throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        SqlNote sqlNote;
+        if (node instanceof TaskList) {
+            if (node.getName().equals(
+                    GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_DEFAULT)) {
+                sqlNote = new SqlNote(mContext, Notes.ID_ROOT_FOLDER);
+            } else if (node.getName().equals(
+                    GTaskStringUtils.MIUI_FOLDER_PREFFIX + GTaskStringUtils.FOLDER_CALL_NOTE)) {
+                sqlNote = new SqlNote(mContext, Notes.ID_CALL_RECORD_FOLDER);
+            } else {
+                sqlNote = new SqlNote(mContext);
+                sqlNote.setContent(node.getLocalJSONFromContent());
+                sqlNote.setParentId(Notes.ID_ROOT_FOLDER);
+            }
+        } else {
+            sqlNote = new SqlNote(mContext);
+            JSONObject js = node.getLocalJSONFromContent();
+            try {
+                if (js.has(GTaskStringUtils.META_HEAD_NOTE)) {
+                    JSONObject note = js.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);
+                    if (note.has(NoteColumns.ID)) {
+                        long id = note.getLong(NoteColumns.ID);
+                        if (DataUtils.existInNoteDatabase(mContentResolver, id)) {
+                            // the id is not available, have to create a new one
+                            note.remove(NoteColumns.ID);
+                        }
+                    }
+                }
+
+                if (js.has(GTaskStringUtils.META_HEAD_DATA)) {
+                    JSONArray dataArray = js.getJSONArray(GTaskStringUtils.META_HEAD_DATA);
+                    for (int i = 0; i < dataArray.length(); i++) {
+                        JSONObject data = dataArray.getJSONObject(i);
+                        if (data.has(DataColumns.ID)) {
+                            long dataId = data.getLong(DataColumns.ID);
+                            if (DataUtils.existInDataDatabase(mContentResolver, dataId)) {
+                                // the data id is not available, have to create
+                                // a new one
+                                data.remove(DataColumns.ID);
+                            }
+                        }
+                    }
+
+                }
+            } catch (JSONException e) {
+                Log.w(TAG, e.toString());
+                e.printStackTrace();
+            }
+            sqlNote.setContent(js);
+
+            Long parentId = mGidToNid.get(((Task) node).getParent().getGid());
+            if (parentId == null) {
+                Log.e(TAG, "cannot find task's parent id locally");
+                throw new ActionFailureException("cannot add local node");
+            }
+            sqlNote.setParentId(parentId.longValue());
+        }
+
+        // create the local node
+        sqlNote.setGtaskId(node.getGid());
+        sqlNote.commit(false);
+
+        // update gid-nid mapping
+        mGidToNid.put(node.getGid(), sqlNote.getId());
+        mNidToGid.put(sqlNote.getId(), node.getGid());
+
+        // update meta
+        updateRemoteMeta(node.getGid(), sqlNote);
+    }
+
+    /**
+     * 功能：update本地node
+     * @author TTS
+     * @param node
+     * ----同步操作的基础数据类型
+     * @param c
+     * ----Cursor
+     * @throws NetworkFailureException
+     */
+    private void updateLocalNode(Node node, Cursor c) throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        SqlNote sqlNote;
+        // update the note locally
+        sqlNote = new SqlNote(mContext, c);
+        sqlNote.setContent(node.getLocalJSONFromContent());
+
+        Long parentId = (node instanceof Task) ? mGidToNid.get(((Task) node).getParent().getGid())
+                : new Long(Notes.ID_ROOT_FOLDER);
+        if (parentId == null) {
+            Log.e(TAG, "cannot find task's parent id locally");
+            throw new ActionFailureException("cannot update local node");
+        }
+        sqlNote.setParentId(parentId.longValue());
+        sqlNote.commit(true);
+
+        // update meta info
+        updateRemoteMeta(node.getGid(), sqlNote);
+    }
+
+    /**
+     * 功能：远程增加Node
+     * 需要updateRemoteMeta
+     * @author TTS
+     * @param node
+     * ----同步操作的基础数据类型
+     * @param c
+     * --Cursor
+     * @throws NetworkFailureException
+     */
+    private void addRemoteNode(Node node, Cursor c) throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        SqlNote sqlNote = new SqlNote(mContext, c);     //从本地mContext中获取内容
+        Node n;
+
+        // update remotely
+        if (sqlNote.isNoteType()) {
+            Task task = new Task();
+            task.setContentByLocalJSON(sqlNote.getContent());
+
+            String parentGid = mNidToGid.get(sqlNote.getParentId());
+            if (parentGid == null) {
+                Log.e(TAG, "cannot find task's parent tasklist");           //调试信息
+                throw new ActionFailureException("cannot add remote task");
+            }
+            mGTaskListHashMap.get(parentGid).addChildTask(task);            //在本地生成的GTaskList中增加子结点
+
+            //登录远程服务器，创建Task
+            GTaskClient.getInstance().createTask(task);
+            n = (Node) task;
+
+            // add meta
+            updateRemoteMeta(task.getGid(), sqlNote);
+        } else {
+            TaskList tasklist = null;
+
+            // we need to skip folder if it has already existed
+            String folderName = GTaskStringUtils.MIUI_FOLDER_PREFFIX;
+            if (sqlNote.getId() == Notes.ID_ROOT_FOLDER)
+                folderName += GTaskStringUtils.FOLDER_DEFAULT;
+            else if (sqlNote.getId() == Notes.ID_CALL_RECORD_FOLDER)
+                folderName += GTaskStringUtils.FOLDER_CALL_NOTE;
+            else
+                folderName += sqlNote.getSnippet();
+
+            //iterator迭代器，通过统一的接口迭代所有的map元素
+            Iterator<Map.Entry<String, TaskList>> iter = mGTaskListHashMap.entrySet().iterator();
+            while (iter.hasNext()) {
+                Map.Entry<String, TaskList> entry = iter.next();
+                String gid = entry.getKey();
+                TaskList list = entry.getValue();
+
+                if (list.getName().equals(folderName)) {
+                    tasklist = list;
+                    if (mGTaskHashMap.containsKey(gid)) {
+                        mGTaskHashMap.remove(gid);
+                    }
+                    break;
+                }
+            }
+
+            // no match we can add now
+            if (tasklist == null) {
+                tasklist = new TaskList();
+                tasklist.setContentByLocalJSON(sqlNote.getContent());
+                GTaskClient.getInstance().createTaskList(tasklist);
+                mGTaskListHashMap.put(tasklist.getGid(), tasklist);
+            }
+            n = (Node) tasklist;
+        }
+
+        // update local note
+        sqlNote.setGtaskId(n.getGid());
+        sqlNote.commit(false);
+        sqlNote.resetLocalModified();
+        sqlNote.commit(true);
+
+        // gid-id mapping                                             //创建id间的映射
+        mGidToNid.put(n.getGid(), sqlNote.getId());
+        mNidToGid.put(sqlNote.getId(), n.getGid());
+    }
+
+    /**
+     * 功能：更新远端的Node，包含meta更新(updateRemoteMeta)
+     * @author TTS
+     * @param node
+     * ----同步操作的基础数据类型
+     * @param c
+     *  --Cursor
+     * @throws NetworkFailureException
+     */
+    private void updateRemoteNode(Node node, Cursor c) throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        SqlNote sqlNote = new SqlNote(mContext, c);
+
+        // update remotely
+        node.setContentByLocalJSON(sqlNote.getContent());
+        GTaskClient.getInstance().addUpdateNode(node);                                //GTaskClient用途为从本地登陆远端服务器 
+
+        // update meta
+        updateRemoteMeta(node.getGid(), sqlNote);
+
+        // move task if necessary
+        if (sqlNote.isNoteType()) {
+            Task task = (Task) node;
+            TaskList preParentList = task.getParent();
+            //preParentList为通过node获取的父节点列表
+
+            String curParentGid = mNidToGid.get(sqlNote.getParentId());
+            //curParentGid为通过光标在数据库中找到sqlNote的mParentId，再通过mNidToGid由long类型转为String类型的Gid
+
+            if (curParentGid == null) {
+                Log.e(TAG, "cannot find task's parent tasklist");
+                throw new ActionFailureException("cannot update remote task");
+            }
+            TaskList curParentList = mGTaskListHashMap.get(curParentGid);
+            //通过HashMap找到对应Gid的TaskList
+
+            if (preParentList != curParentList) {                                          //?????????????
+                preParentList.removeChildTask(task);
+                curParentList.addChildTask(task);
+                GTaskClient.getInstance().moveTask(task, preParentList, curParentList);
+            }
+        }
+
+        // clear local modified flag
+        sqlNote.resetLocalModified();
+        //commit到本地数据库
+        sqlNote.commit(true);
+    }
+
+    /**
+     * 功能：升级远程meta。  meta---元数据----计算机文件系统管理数据---管理数据的数据。
+     * @author TTS
+     * @param gid
+     * ---GoogleID为String类型
+     * @param sqlNote
+     * ---同步前的数据库操作，故使用类SqlNote
+     * @throws NetworkFailureException
+     */
+    private void updateRemoteMeta(String gid, SqlNote sqlNote) throws NetworkFailureException {
+        if (sqlNote != null && sqlNote.isNoteType()) {
+            MetaData metaData = mMetaHashMap.get(gid);
+            if (metaData != null) {
+                metaData.setMeta(gid, sqlNote.getContent());
+                GTaskClient.getInstance().addUpdateNode(metaData);
+            } else {
+                metaData = new MetaData();
+                metaData.setMeta(gid, sqlNote.getContent());
+                mMetaList.addChildTask(metaData);
+                mMetaHashMap.put(gid, metaData);
+                GTaskClient.getInstance().createTask(metaData);
+            }
+        }
+    }
+
+    /**
+     * 功能：刷新本地，给sync的ID对应上最后更改过的对象
+     * @author TTS
+     * @return void
+     * @throws NetworkFailureException
+     */
+    private void refreshLocalSyncId() throws NetworkFailureException {
+        if (mCancelled) {
+            return;
+        }
+
+        // get the latest gtask list                                               //获取最近的（最晚的）gtask list
+        mGTaskHashMap.clear();
+        mGTaskListHashMap.clear();
+        mMetaHashMap.clear();
+        initGTaskList();
+
+        Cursor c = null;
+        try {
+            c = mContentResolver.query(Notes.CONTENT_NOTE_URI, SqlNote.PROJECTION_NOTE,
+                    "(type<>? AND parent_id<>?)", new String[] {
+                            String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)
+                    }, NoteColumns.TYPE + " DESC");                                                 //query语句：五个参数，NoteColumns.TYPE + " DESC"-----为按类型递减顺序返回查询结果。new String[] {String.valueOf(Notes.TYPE_SYSTEM), String.valueOf(Notes.ID_TRASH_FOLER)}------为选择参数。"(type<>? AND parent_id<>?)"-------指明返回行过滤器。SqlNote.PROJECTION_NOTE--------应返回的数据列的名字。Notes.CONTENT_NOTE_URI--------contentProvider包含所有数据集所对应的uri
+            if (c != null) {
+                while (c.moveToNext()) {
+                    String gid = c.getString(SqlNote.GTASK_ID_COLUMN);
+                    Node node = mGTaskHashMap.get(gid);
+                    if (node != null) {
+                        mGTaskHashMap.remove(gid);
+                        ContentValues values = new ContentValues();                     //在ContentValues中创建键值对。准备通过contentResolver写入数据
+                        values.put(NoteColumns.SYNC_ID, node.getLastModified());
+                        mContentResolver.update(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI,   //进行批量更改，选择参数为NULL，应该可以用insert替换，参数分别为表名和需要更新的value对象。
+                                c.getLong(SqlNote.ID_COLUMN)), values, null, null);
+                    } else {
+                        Log.e(TAG, "something is missed");
+                        throw new ActionFailureException(
+                                "some local items don't have gid after sync");
+                    }
+                }
+            } else {
+                Log.w(TAG, "failed to query local note to refresh sync id");
+            }
+        } finally {
+            if (c != null) {
+                c.close();
+                c = null;
+            }
+        }
+    }
+
+    /**
+     * 功能：获取同步账号,mAccount.name
+     * @author TTS
+     * @return String
+     */
+    public String getSyncAccount() {
+        return GTaskClient.getInstance().getSyncAccount().name;
+    }
+
+    /**
+     * 功能：取消同步，置mCancelled为true
+     * @author TTS
+     */
+    public void cancelSync() {
+        mCancelled = true;
+    }
+}