package net.micode.notes.data;
 
import android.content.Context;
 
import android.database.Cursor;
import android.provider.ContactsContract.CommonDataKinds.Phone;
import android.provider.ContactsContract.Data;
import android.telephony.PhoneNumberUtils;
import android.util.Log;
 
import java.util.HashMap;
//change
public class Contact { //联系人
    private static HashMap<String, String> sContactCache;
    private static final String TAG = "Contact";
 
    // 定义字符串CALLER_ID_SELECTION
    private static final String CALLER_ID_SELECTION = "PHONE_NUMBERS_EQUAL(" 
 
+ Phone.NUMBER
    + ",?) AND " + Data.MIMETYPE + "='" + Phone.CONTENT_ITEM_TYPE + "'"
    + " AND " + Data.RAW_CONTACT_ID + " IN "
            + "(SELECT raw_contact_id "
            + " FROM phone_lookup"
            + " WHERE min_match = '+')";
    
    // 获取联系人
    public static String getContact(Context context, String phoneNumber) {
        if(sContactCache == null) {
            sContactCache = new HashMap<String, String>();
        }
        
        // 查找HashMap中是否已有phoneNumber信息
        if(sContactCache.containsKey(phoneNumber)) {
            return sContactCache.get(phoneNumber);
        }
 
        String selection = CALLER_ID_SELECTION.replace("+",
                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
        // 查找数据库中phoneNumber的信息
        Cursor cursor = context.getContentResolver().query(
                Data.CONTENT_URI,
                new String [] { Phone.DISPLAY_NAME },
                selection,
                new String[] { phoneNumber },
                null);
        
        // 判定查询结果 
        // moveToFirst()返回第一条
        if (cursor != null && cursor.moveToFirst()) {
            try {
            // 找到相关信息
                String name = cursor.getString(0);
                sContactCache.put(phoneNumber, name);
                return name;
            // 异常
            } catch (IndexOutOfBoundsException e) {
                Log.e(TAG, " Cursor get string error " + e.toString());
                return null;
            } finally {
                cursor.close();
            }
            // 未找到相关信息
        } else {
            Log.d(TAG, "No contact matched with number:" + phoneNumber);
            return null;
        }
    }
}
package net.micode.notes.data;
 
import android.content.ContentUris;
import android.net.Uri;
// Notes 类中定义了很多常量，这些常量大多是int型和string型
public class Notes {
    public static final String AUTHORITY = "micode_notes";
    public static final String TAG = "Notes";
    
    //以下三个常量对NoteColumns.TYPE的值进行设置时会用到
    public static final int TYPE_NOTE     = 0;
    public static final int TYPE_FOLDER   = 1;
    public static final int TYPE_SYSTEM   = 2;
 
    /**
     * Following IDs are system folders' identifiers
     * {@link Notes#ID_ROOT_FOLDER } is default folder
     * {@link Notes#ID_TEMPARAY_FOLDER } is for notes belonging no folder
     * {@link Notes#ID_CALL_RECORD_FOLDER} is to store call records
     */
    public static final int ID_ROOT_FOLDER = 0;
    public static final int ID_TEMPARAY_FOLDER = -1;
    public static final int ID_CALL_RECORD_FOLDER = -2;
    public static final int ID_TRASH_FOLER = -3;
 
    public static final String INTENT_EXTRA_ALERT_DATE = 
 
"net.micode.notes.alert_date";
    public static final String INTENT_EXTRA_BACKGROUND_ID = 
 
"net.micode.notes.background_color_id";
    public static final String INTENT_EXTRA_WIDGET_ID = 
 
"net.micode.notes.widget_id";
    public static final String INTENT_EXTRA_WIDGET_TYPE = 
 
"net.micode.notes.widget_type";
    public static final String INTENT_EXTRA_FOLDER_ID = 
 
"net.micode.notes.folder_id";
    public static final String INTENT_EXTRA_CALL_DATE = 
 
"net.micode.notes.call_date";
 
    public static final int TYPE_WIDGET_INVALIDE      = -1;
    public static final int TYPE_WIDGET_2X            = 0;
    public static final int TYPE_WIDGET_4X            = 1;
 
    public static class DataConstants {
        public static final String NOTE = TextNote.CONTENT_ITEM_TYPE;
        public static final String CALL_NOTE = CallNote.CONTENT_ITEM_TYPE;
    }
 
    /**
     * Uri to query all notes and folders
     */
    public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" + 
 
AUTHORITY + "/note");//定义查询便签和文件夹的指针。
 
//    public static final Uri my_URI = ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI , 10);
   
    /**
     * Uri to query data
     */
    public static final Uri CONTENT_DATA_URI = Uri.parse("content://" + 
 
AUTHORITY + "/data");//定义查找数据的指针。
 
    // 定义NoteColumns的常量,用于后面创建数据库的表头
    public interface NoteColumns {
        /**
         * The unique ID for a row
         * <P> Type: INTEGER (long) </P>
         */
        public static final String ID = "_id";
 
        /**
         * The parent's id for note or folder
         * <P> Type: INTEGER (long) </P>
         */
        public static final String PARENT_ID = "parent_id";//为什么会有parent_id
 
        /**
         * Created data for note or folder
         * <P> Type: INTEGER (long) </P>
         */
        public static final String CREATED_DATE = "created_date";
 
        /**
         * Latest modified date
         * <P> Type: INTEGER (long) </P>
         */
        public static final String MODIFIED_DATE = "modified_date";
 
 
        /**
         * Alert date
         * <P> Type: INTEGER (long) </P>
         */
        public static final String ALERTED_DATE = "alert_date";
 
        /**
         * Folder's name or text content of note
         * <P> Type: TEXT </P>
         */
        public static final String SNIPPET = "snippet";
 
        /**
         * Note's widget id
         * <P> Type: INTEGER (long) </P>
         */
        public static final String WIDGET_ID = "widget_id";
 
        /**
         * Note's widget type
         * <P> Type: INTEGER (long) </P>
         */
        public static final String WIDGET_TYPE = "widget_type";
 
        /**
         * Note's background color's id
         * <P> Type: INTEGER (long) </P>
         */
        public static final String BG_COLOR_ID = "bg_color_id";
 
        /**
         * For text note, it doesn't has attachment, for multi-media
         * note, it has at least one attachment
         * <P> Type: INTEGER </P>
         */
        public static final String HAS_ATTACHMENT = "has_attachment";
 
        /**
         * Folder's count of notes
         * <P> Type: INTEGER (long) </P>
         */
        public static final String NOTES_COUNT = "notes_count";
 
        /**
         * The file type: folder or note
         * <P> Type: INTEGER </P>
         */
        public static final String TYPE = "type";
 
        /**
         * The last sync id
         * <P> Type: INTEGER (long) </P>
         */
        public static final String SYNC_ID = "sync_id";//同步
 
        /**
         * Sign to indicate local modified or not
         * <P> Type: INTEGER </P>
         */
        public static final String LOCAL_MODIFIED = "local_modified";
 
        /**
         * Original parent id before moving into temporary folder
         * <P> Type : INTEGER </P>
         */
        public static final String ORIGIN_PARENT_ID = "origin_parent_id";
 
        /**
         * The gtask id
         * <P> Type : TEXT </P>
         */
        public static final String GTASK_ID = "gtask_id";
 
        /**
         * The version code
         * <P> Type : INTEGER (long) </P>
         */
        public static final String VERSION = "version";
    }//这些常量主要是定义便签的属性的。
 
    // 定义DataColumns的常量,用于后面创建数据库的表头
    public interface DataColumns {
        /**
         * The unique ID for a row
         * <P> Type: INTEGER (long) </P>
         */
        public static final String ID = "_id";
 
        /**
         * The MIME type of the item represented by this row.
         * <P> Type: Text </P>
         */
        public static final String MIME_TYPE = "mime_type";
 
        /**
         * The reference id to note that this data belongs to
         * <P> Type: INTEGER (long) </P>
         */
        public static final String NOTE_ID = "note_id";
 
        /**
         * Created data for note or folder
         * <P> Type: INTEGER (long) </P>
         */
        public static final String CREATED_DATE = "created_date";
 
        /**
         * Latest modified date
         * <P> Type: INTEGER (long) </P>
         */
        public static final String MODIFIED_DATE = "modified_date";
 
        /**
         * Data's content
         * <P> Type: TEXT </P>
         */
        public static final String CONTENT = "content";
 
 
        /**
         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
used for
         * integer data type
         * <P> Type: INTEGER </P>
         */
        public static final String DATA1 = "data1";
 
        /**
         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
used for
         * integer data type
         * <P> Type: INTEGER </P>
         */
        public static final String DATA2 = "data2";
 
        /**
         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
used for
         * TEXT data type
         * <P> Type: TEXT </P>
         */
        public static final String DATA3 = "data3";
 
        /**
         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
used for
         * TEXT data type
         * <P> Type: TEXT </P>
         */
        public static final String DATA4 = "data4";
 
        /**
         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
used for
         * TEXT data type
         * <P> Type: TEXT </P>
         */
        public static final String DATA5 = "data5";
    }//主要是定义存储便签内容数据的
    public static final class TextNote implements DataColumns {
        /**
         * Mode to indicate the text in check list mode or not
         * <P> Type: Integer 1:check list mode 0: normal mode </P>
         */
        public static final String MODE = DATA1;
 
        public static final int MODE_CHECK_LIST = 1;
 
        public static final String CONTENT_TYPE = 
 
"vnd.android.cursor.dir/text_note";
 
        public static final String CONTENT_ITEM_TYPE = 
 
"vnd.android.cursor.item/text_note";
 
        public static final Uri CONTENT_URI = Uri.parse("content://" + 
 
AUTHORITY + "/text_note");
    }//文本内容的数据结构
 
    public static final class CallNote implements DataColumns {
        /**
         * Call date for this record
         * <P> Type: INTEGER (long) </P>
         */
        public static final String CALL_DATE = DATA1;
 
        /**
         * Phone number for this record
         * <P> Type: TEXT </P>
         */
        public static final String PHONE_NUMBER = DATA3;
 
        public static final String CONTENT_TYPE = 
 
"vnd.android.cursor.dir/call_note";
 
        public static final String CONTENT_ITEM_TYPE = 
 
"vnd.android.cursor.item/call_note";
 
        public static final Uri CONTENT_URI = Uri.parse("content://" + 
 
AUTHORITY + "/call_note");
    }//电话内容的数据结构
}
package net.micode.notes.data;
 
import android.content.ContentValues;//就是用于保存一些数据（string boolean byte double float int long short ...）信息，这些信息可以被数据库操作时使用。
import android.content.Context;//加载和访问资源。（android中主要是这两个功能，但是这里具体不清楚）
import android.database.sqlite.SQLiteDatabase;//主要提供了对应于添加、删除、更新、查询的操作方法： insert()、delete()、update()和query()。配合content.values
import android.database.sqlite.SQLiteOpenHelper;//用来管理数据的创建和版本更新
import android.util.Log;
 
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.DataConstants;
import net.micode.notes.data.Notes.NoteColumns;
//数据库操作，用SQLOpenhelper,对一些note和文件进行数据库的操作，比如删除文件后，将文件里的note也相应删除
 
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "note.db";
 
    private static final int DB_VERSION = 4;
 
    public interface TABLE {    //接口，分成note和data，在后面的程序里分别使用过
        public static final String NOTE = "note";
 
        public static final String DATA = "data";
    }
 
    private static final String TAG = "NotesDatabaseHelper";
 
    private static NotesDatabaseHelper mInstance;
 
    private static final String CREATE_NOTE_TABLE_SQL =
        "CREATE TABLE " + TABLE.NOTE + "(" +
            NoteColumns.ID + " INTEGER PRIMARY KEY," +
            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
        ")";//数据库中需要存储的项目的名称，就相当于创建一个表格的表头的内容。
 
    private static final String CREATE_DATA_TABLE_SQL =
        "CREATE TABLE " + TABLE.DATA + "(" +
            DataColumns.ID + " INTEGER PRIMARY KEY," +
            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
            DataColumns.DATA1 + " INTEGER," +
            DataColumns.DATA2 + " INTEGER," +
            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
        ")";//和上面的功能一样，主要是存储的项目不同
 
    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";//存储便签编号的一个数据表格
 
    /**
     * Increase folder's note count when move note to the folder
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER increase_folder_count_on_update "+
        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
        " END";//在文件夹中移入一个Note之后需要更改的数据的表格。
 
    /**
     * Decrease folder's note count when move note from folder
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER decrease_folder_count_on_update " +
        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
        "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
        " END";//在文件夹中移出一个Note之后需要更改的数据的表格。
 
    /**
     * Increase folder's note count when insert new note to the folder
     */
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
        "CREATE TRIGGER increase_folder_count_on_insert " +
        " AFTER INSERT ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
        " END";//在文件夹中插入一个Note之后需要更改的数据的表格。
 
    /**
     * Decrease folder's note count when delete note from the folder
     */
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER decrease_folder_count_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
        "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
        " END";//在文件夹中删除一个Note之后需要更改的数据的表格。
 
    /**
     * Update note's content when insert data with type {@link DataConstants#NOTE}
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
        "CREATE TRIGGER update_note_content_on_insert " +
        " AFTER INSERT ON " + TABLE.DATA +
        " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
        " END";//在文件夹中对一个Note导入新的数据之后需要更改的数据的表格。
 
    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has changed
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_update " +
        " AFTER UPDATE ON " + TABLE.DATA +
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
        " END";//Note数据被修改后需要更改的数据的表格。
 
    /**
     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
     */
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_delete " +
        " AFTER delete ON " + TABLE.DATA +
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=''" +
        "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
        " END";//Note数据被删除后需要更改的数据的表格。
 
    /**
     * Delete datas belong to note which has been deleted
     */
    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
        "CREATE TRIGGER delete_data_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN" +
        "  DELETE FROM " + TABLE.DATA +
        "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
        " END";//删除已删除的便签的数据后需要更改的数据的表格。
 
    /**
     * Delete notes belong to folder which has been deleted
     */
    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
        "CREATE TRIGGER folder_delete_notes_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN" +
        "  DELETE FROM " + TABLE.NOTE +
        "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
        " END";//删除已删除的文件夹的便签后需要更改的数据的表格。
 
    /**
     * Move notes belong to folder which has been moved to trash folder
     */
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
        "CREATE TRIGGER folder_move_notes_on_trash " +
        " AFTER UPDATE ON " + TABLE.NOTE +
        " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
        "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
        " END";//还原垃圾桶中便签后需要更改的数据的表格。
 
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }//构造函数，传入数据库的名称和版本
 
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL);
        reCreateNoteTableTriggers(db);
        createSystemFolder(db);
        Log.d(TAG, "note table has been created");
    }//创建表格（用来存储标签属性）
 
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");
 
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER);
        db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER);
        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
    }//execSQL是数据库操作的API，主要是更改行为的SQL语句。
    //在这里主要是用来重新创建上述定义的表格用的，先删除原来有的数据库的触发器再重新创建新的数据库
 
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues();
 
        /**
         * call record foler for call notes
         */
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
 
        /**
         * root folder which is default folder
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
 
        /**
         * temporary folder which is used for moving note
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
 
        /**
         * create trash folder
         */
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }//创建几个系统文件夹
 
    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL);
        reCreateDataTableTriggers(db);
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
        Log.d(TAG, "data table has been created");
    }//创建表格（用来存储标签内容）
 
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");
 
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
    }//同上面的execSQL
 
    static synchronized NotesDatabaseHelper getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new NotesDatabaseHelper(context);
        }
        return mInstance;
    }//上网查是为解决同一时刻只能有一个线程执行.
     //在写程序库代码时，有时有一个类需要被所有的其它类使用，
     //但又要求这个类只能被实例化一次，是个服务类，定义一次，其它类使用同一个这个类的实例
 
    @Override
    public void onCreate(SQLiteDatabase db) {
        createNoteTable(db);
        createDataTable(db);
    }//实现两个表格（上面创建的两个表格）
 
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        boolean reCreateTriggers = false;
        boolean skipV2 = false;
 
        if (oldVersion == 1) {
            upgradeToV2(db);
            skipV2 = true; // this upgrade including the upgrade from v2 to v3
            oldVersion++;
        }
 
        if (oldVersion == 2 && !skipV2) {
            upgradeToV3(db);
            reCreateTriggers = true;
            oldVersion++;
        }
 
        if (oldVersion == 3) {
            upgradeToV4(db);
            oldVersion++;
        }
 
        if (reCreateTriggers) {
            reCreateNoteTableTriggers(db);
            reCreateDataTableTriggers(db);
        }
 
        if (oldVersion != newVersion) {
            throw new IllegalStateException("Upgrade notes database to version " + newVersion
                    + "fails");
        }
    }//数据库版本的更新（数据库内容的更改）
 
    private void upgradeToV2(SQLiteDatabase db) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
        createNoteTable(db);
        createDataTable(db);
    }//更新到V2版本
 
    private void upgradeToV3(SQLiteDatabase db) {
        // drop unused triggers
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");
        // add a column for gtask id
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                + " TEXT NOT NULL DEFAULT ''");
        // add a trash system folder
        ContentValues values = new ContentValues();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }//更新到V3版本
 
    private void upgradeToV4(SQLiteDatabase db) {
        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                + " INTEGER NOT NULL DEFAULT 0");
    }//更新到V4版本,但是不知道V2、V3、V4是什么意思
}
package net.micode.notes.data;
 
import android.app.SearchManager;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Intent;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;
 
import net.micode.notes.R;
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.NoteColumns;
import net.micode.notes.data.NotesDatabaseHelper.TABLE;
//为存储和获取数据提供接口。可以在不同的应用程序之间共享数据
//ContentProvider提供的方法
//query：查询
//insert：插入
//update：更新
//delete：删除
//getType：得到数据类型
public class NotesProvider extends ContentProvider {
	// UriMatcher用于匹配Uri
    private static final UriMatcher mMatcher;
 
    private NotesDatabaseHelper mHelper;
 
    private static final String TAG = "NotesProvider";
 
    private static final int URI_NOTE            = 1;
    private static final int URI_NOTE_ITEM       = 2;
    private static final int URI_DATA            = 3;
    private static final int URI_DATA_ITEM       = 4;
 
    private static final int URI_SEARCH          = 5;
    private static final int URI_SEARCH_SUGGEST  = 6;
 
    static {
    	// 创建UriMatcher时，调用UriMatcher(UriMatcher.NO_MATCH)表示不匹配任何路径的返回码
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 把需要匹配Uri路径全部给注册上
        mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
        mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM);
        mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA);
        mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM);
        mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH);
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST);
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST);
    }
 
    /**
     * x'0A' represents the '\n' character in sqlite. For title and content in the search result,
     * we will trim '\n' and white space in order to show more information.
     */
    // 声明 NOTES_SEARCH_PROJECTION
    private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + ","
        + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + ","
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + ","
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + ","
        + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + ","
        + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + ","
        + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA;
    // 声明NOTES_SNIPPET_SEARCH_QUERY
    private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
        + " FROM " + TABLE.NOTE
        + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
        + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
        + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
 
    @Override
    // Context只有在onCreate()中才被初始化
    // 对mHelper进行实例化
    public boolean onCreate() {
        mHelper = NotesDatabaseHelper.getInstance(getContext());
        return true;
    }
 
    @Override
    // 查询uri在数据库中对应的位置
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        Cursor c = null;
        // 获取可读数据库
        SQLiteDatabase db = mHelper.getReadableDatabase();
        String id = null;
        // 匹配查找uri
        switch (mMatcher.match(uri)) {
        	// 对于不同的匹配值，在数据库中查找相应的条目
            case URI_NOTE:
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1);
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_DATA:
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_DATA_ITEM:
                id = uri.getPathSegments().get(1);
                c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_SEARCH:
            case URI_SEARCH_SUGGEST:
                if (sortOrder != null || projection != null) {
                	// 不合法的参数异常
                    throw new IllegalArgumentException(
                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
                }
 
                String searchString = null;
                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
                    if (uri.getPathSegments().size() > 1) {
                    	// getPathSegments()方法得到一个String的List，
                    	// 在uri.getPathSegments().get(1)为第2个元素
                        searchString = uri.getPathSegments().get(1);
                    }
                } else {
                    searchString = uri.getQueryParameter("pattern");
                }
 
                if (TextUtils.isEmpty(searchString)) {
                    return null;
                }
 
                try {
                    searchString = String.format("%%%s%%", searchString);
                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
                            new String[] { searchString });
                } catch (IllegalStateException ex) {
                    Log.e(TAG, "got exception: " + ex.toString());
                }
                break;
            default:
            	// 抛出异常
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        if (c != null) {
            c.setNotificationUri(getContext().getContentResolver(), uri);
        }
        return c;
    }
 
    @Override
    // 插入一个uri
    public Uri insert(Uri uri, ContentValues values) {
    	// 获得可写的数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        long dataId = 0, noteId = 0, insertedId = 0;
        switch (mMatcher.match(uri)) {
        	// 新增一个条目
            case URI_NOTE:
                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
                break;
            // 如果存在，查找NOTE_ID
            case URI_DATA:
                if (values.containsKey(DataColumns.NOTE_ID)) {
                    noteId = values.getAsLong(DataColumns.NOTE_ID);
                } else {
                    Log.d(TAG, "Wrong data format without note id:" + values.toString());
                }
                insertedId = dataId = db.insert(TABLE.DATA, null, values);
                break;
           default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        // Notify the note uri
        // notifyChange获得一个ContextResolver对象并且更新里面的内容
        if (noteId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
        }
 
        // Notify the data uri
        if (dataId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
        }
 
        // 返回插入的uri的路径
        return ContentUris.withAppendedId(uri, insertedId);
    }
 
    @Override
    // 删除一个uri
    public int delete(Uri uri, String selection, String[] selectionArgs) {
    	//Uri代表要操作的数据，Android上可用的每种资源 -包括 图像、视频片段、音频资源等都可以用Uri来表示。
        int count = 0;
        String id = null;
        // 获得可写的数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean deleteData = false;
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
                count = db.delete(TABLE.NOTE, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1);
                /**
                 * ID that smaller than 0 is system folder which is not allowed to
                 * trash
                 */
                long noteId = Long.valueOf(id);
                if (noteId <= 0) {
                    break;
                }
                count = db.delete(TABLE.NOTE,
                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA:
                count = db.delete(TABLE.DATA, selection, selectionArgs);
                deleteData = true;
                break;
            case URI_DATA_ITEM:
                id = uri.getPathSegments().get(1);
                count = db.delete(TABLE.DATA,
                        DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                deleteData = true;
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        if (count > 0) {
            if (deleteData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }
 
    @Override
    // 更新一个uri
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean updateData = false;
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                increaseNoteVersion(-1, selection, selectionArgs);
                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1);
                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs);
                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA:
                count = db.update(TABLE.DATA, values, selection, selectionArgs);
                updateData = true;
                break;
            case URI_DATA_ITEM:
                id = uri.getPathSegments().get(1);
                count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                updateData = true;
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
 
        if (count > 0) {
            if (updateData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }
    
    // 将字符串解析成规定格式
    private String parseSelection(String selection) {
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
    }
    
    //增加一个noteVersion
    private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
        StringBuilder sql = new StringBuilder(120);
        sql.append("UPDATE ");
        sql.append(TABLE.NOTE);
        sql.append(" SET ");
        sql.append(NoteColumns.VERSION);
        sql.append("=" + NoteColumns.VERSION + "+1 ");
 
        if (id > 0 || !TextUtils.isEmpty(selection)) {
            sql.append(" WHERE ");
        }
        if (id > 0) {
            sql.append(NoteColumns.ID + "=" + String.valueOf(id));
        }
        if (!TextUtils.isEmpty(selection)) {
            String selectString = id > 0 ? parseSelection(selection) : selection;
            for (String args : selectionArgs) {
                selectString = selectString.replaceFirst("\\?", args);
            }
            sql.append(selectString);
        }
        
        // execSQL()方法可以执行insert、delete、update和CREATE TABLE之类有更改行为的SQL语句
        mHelper.getWritableDatabase().execSQL(sql.toString());
    }
 
    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }
 
}