123456/java/net/micode/notes/tool/BackupUtils.java

/*
 * 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.
 * 函数分析
getInstance方法
所属类：BackupUtils
功能：实现单例模式，若实例sInstance为空，则创建并返回新的BackupUtils实例（传入Context进行初始化），若不为空则直接返回已有实例，保证整个应用中该工具类只有一个实例在运作。
externalStorageAvailable方法
所属类：BackupUtils
功能：通过判断外部存储（通常是 SD 卡）的挂载状态是否为Environment.MEDIA_MOUNTED，来返回外部存储是否可用的布尔值，为后续备份操作判断能否将数据写入外部存储做准备。
exportToText方法
所属类：BackupUtils
功能：调用内部TextExport类的exportToText方法来执行将笔记数据导出为文本的实际操作，并返回相应的状态码（如成功、外部存储未挂载、系统错误等），外部代码可据此知晓此次导出操作的结果情况。
getExportedTextFileName方法
所属类：BackupUtils
功能：返回内部TextExport类中记录的导出文本文件名（mFileName），方便外部获取导出文件的名称信息，比如用于展示给用户或者进行后续文件相关的操作提示等。
getExportedTextFileDir方法
所属类：BackupUtils
功能：返回内部TextExport类中记录的导出文本文件所在目录（mFileDirectory），用于知晓文件保存的路径情况，像在日志记录或者引导用户查找备份文件时能提供相应的目录信息。
TextExport类相关函数
构造函数：
所属类：TextExport（BackupUtils的内部类）
功能：初始化TEXT_FORMAT数组，从资源中获取格式化字符串数组用于后续文本格式化输出，同时保存传入的Context，并初始化文件名和文件目录为空字符串，为后续操作准备相关数据和资源引用。
getFormat方法：
所属类：TextExport（BackupUtils的内部类）
功能：根据传入的id参数，从TEXT_FORMAT数组中获取对应的格式化字符串并返回，用于在文本输出时按照特定格式拼接内容，比如格式化日期、内容等信息。
exportFolderToText方法：
所属类：TextExport（BackupUtils的内部类）
功能：依据传入的文件夹ID查询属于该文件夹的笔记游标，若游标不为null且有数据，遍历游标，先按格式输出笔记的修改日期，再根据笔记ID调用exportNoteToText方法输出笔记具体内容，最后关闭游标，实现将指定文件夹下所有笔记数据输出到给定的打印流中的功能。
exportNoteToText方法：
所属类：TextExport（BackupUtils的内部类）
功能：依据传入的笔记ID查询该笔记附属数据的游标，若游标不为null且有数据，遍历游标，根据数据的MIME_TYPE判断类型（如通话记录、普通笔记等），按照对应格式输出相应数据（如电话号码、通话日期、笔记内容等），游标遍历完后关闭游标，并输出换行分隔符，完成单个笔记相关数据的文本输出操作。
exportToText方法：
所属类：TextExport（BackupUtils的内部类）
功能：首先判断外部存储是否可用，不可用则返回对应状态码；接着获取用于输出文本的打印流，若获取失败返回系统错误状态码；然后分别查询符合特定条件的文件夹游标、根文件夹下笔记游标，遍历游标并调用相应的导出方法（exportFolderToText、exportNoteToText）输出数据，最后关闭打印流并返回成功状态码，整体实现将笔记数据按规则导出为文本文件的完整流程。
getExportToTextPrintStream方法：
所属类：TextExport（BackupUtils的内部类）
功能：先创建一个基于外部存储指定路径和文件名（文件名含当前日期格式化信息）的文件，若创建失败则返回null，成功则记录文件名和文件目录信息，再尝试创建文件输出流并基于此构建打印流，若过程出现异常则返回null，最终返回构建好的用于输出文本的打印流，为文本导出提供输出流对象。
generateFileMountedOnSDcard方法
所属类：BackupUtils
功能：根据传入的资源ID（用于指定文件路径、文件名格式）构建文件对象，先创建文件所在目录（若不存在），再创建文件本身（若不存在），若过程出现安全或IO异常则返回null，否则返回构建好的文件对象，用于在外部存储上生成保存备份数据的文本文件。
 */

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";
    // Singleton stuff
    private static BackupUtils sInstance;

    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;

    private BackupUtils(Context context) {
        mTextExport = new TextExport(context);
    }

    private static boolean externalStorageAvailable() {
        return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());
    }

    public int exportToText() {
        return mTextExport.exportToText();
    }

    public String getExportedTextFileName() {
        return mTextExport.mFileName;
    }

    public String getExportedTextFileDir() {
        return mTextExport.mFileDirectory;
    }

    private static class TextExport {
        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;

        public TextExport(Context context) {
            TEXT_FORMAT = context.getResources().getStringArray(R.array.format_for_exported_note);
            mContext = context;
            mFileName = "";
            mFileDirectory = "";
        }

        private String getFormat(int id) {
            return TEXT_FORMAT[id];
        }

        /**
         * Export the folder identified by folder id to text
         */
        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
         */
        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
         */
        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}
         */
        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
     */
    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;
    }
}