xiaomi/src/net/micode/notes/data/NotesProvider.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.
 */
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;  
  
// 自定义ContentProvider，用于提供对Notes数据库的访问  
public class NotesProvider extends ContentProvider {  
    // Uri匹配器，用于区分不同的URI请求  
    private static final UriMatcher mMatcher;  
  
    // 数据库帮助类实例，用于操作数据库  
    private NotesDatabaseHelper mHelper;  
  
    // 日志标签  
    private static final String TAG = "NotesProvider";  
  
    // 定义不同的URI类型  
    private static final int URI_NOTE = 1;            // 笔记集合URI  
    private static final int URI_NOTE_ITEM = 2;       // 单个笔记URI  
    private static final int URI_DATA = 3;            // 笔记数据集合URI  
    private static final int URI_DATA_ITEM = 4;       // 单个笔记数据URI  
    private static final int URI_SEARCH = 5;          // 搜索URI  
    private static final int URI_SEARCH_SUGGEST = 6;  // 搜索建议URI  
  
    // 静态代码块，初始化UriMatcher  
    static {  
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);  
        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);  
    }  
  
    // 搜索投影列，用于搜索建议  
    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;  
  
    // 搜索查询语句  
    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;  
  
    // ContentProvider创建时调用  
    @Override  
    public boolean onCreate() {  
        mHelper = NotesDatabaseHelper.getInstance(getContext());  
        return true;  
    }  
  
    // 查询方法  
    @Override  
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,  
            String sortOrder) {  
        Cursor c = null;  
        SQLiteDatabase db = mHelper.getReadableDatabase();  
        String id = null;  
        // 根据URI类型执行不同的查询操作  
        switch (mMatcher.match(uri)) {  
            case URI_NOTE:  
                // 查询笔记集合  
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,  
                        sortOrder);  
                break;  
            case URI_NOTE_ITEM:  
                // 查询单个笔记  
                id = uri.getPathSegments().get(1);  
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id  
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);  
                break;  
            case URI_DATA:  
                // 查询笔记数据集合  
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,  
                        sortOrder);  
                break;  
            case URI_DATA_ITEM:  
                // 查询单个笔记数据  
                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:  
                // 搜索或搜索建议，不允许指定排序、选择条件等  
                if (sortOrder != null || projection != null) {  
                    throw new IllegalArgumentException(  
                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");  
                }  
                // 注意：此处缺少实现搜索或搜索建议的代码  
                break;  
        }  
        // 注意：此处缺少返回Cursor前的null检查和处理代码  
        return c;  
    }  
  
    // 注意：其他如insert, update, delete, getType等方法未展示，需根据需求实现  
}
// 这是一个自定义的ContentProvider类的一部分，用于处理对数据库内容的插入、删除、更新和查询操作。  

    // 插入数据到数据库  
    @Override  
    public Uri insert(Uri uri, ContentValues values) {  
        // 获取可写的数据库实例  
        SQLiteDatabase db = mHelper.getWritableDatabase();  
        long dataId = 0, noteId = 0, insertedId = 0;  
          
        // 根据URI匹配器的结果决定插入到哪个表  
        switch (mMatcher.match(uri)) {  
            case URI_NOTE: // 如果是笔记URI  
                insertedId = noteId = db.insert(TABLE.NOTE, null, values); // 插入到笔记表  
                break;  
            case URI_DATA: // 如果是数据URI  
                if (values.containsKey(DataColumns.NOTE_ID)) { // 如果包含笔记ID  
                    noteId = values.getAsLong(DataColumns.NOTE_ID); // 获取笔记ID  
                } else {  
                    Log.d(TAG, "Wrong data format without note id:" + values.toString()); // 记录错误日志  
                }  
                insertedId = dataId = db.insert(TABLE.DATA, null, values); // 插入到数据表  
                break;  
            default:  
                throw new IllegalArgumentException("Unknown URI " + uri); // 如果URI未知，抛出异常  
        }  
          
        // 如果插入了笔记，通知监听器  
        if (noteId > 0) {  
            getContext().getContentResolver().notifyChange(  
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);  
        }  
  
        // 如果插入了数据，通知监听器  
        if (dataId > 0) {  
            getContext().getContentResolver().notifyChange(  
                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);  
        }  
  
        // 返回新插入数据的URI  
        return ContentUris.withAppendedId(uri, insertedId);  
    }  
  
    // 从数据库中删除数据  
    @Override  
    public int delete(Uri uri, String selection, String[] selectionArgs) {  
        int count = 0;  
        String id = null;  
        SQLiteDatabase db = mHelper.getWritableDatabase();  
        boolean deleteData = false;  
          
        // 根据URI匹配器的结果决定从哪个表删除数据  
        switch (mMatcher.match(uri)) {  
            case URI_NOTE: // 如果是笔记URI  
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 "; // 添加额外的筛选条件  
                count = db.delete(TABLE.NOTE, selection, selectionArgs); // 从笔记表删除  
                break;  
            case URI_NOTE_ITEM: // 如果是单个笔记项的URI  
                id = uri.getPathSegments().get(1); // 获取笔记ID  
                long noteId = Long.valueOf(id);  
                if (noteId <= 0) {  
                    break; // 如果ID无效，则不执行删除  
                }  
                count = db.delete(TABLE.NOTE,  
                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs); // 从笔记表删除单个项  
                break;  
            case URI_DATA: // 如果是数据URI  
                count = db.delete(TABLE.DATA, selection, selectionArgs); // 从数据表删除  
                deleteData = true; // 标记为删除了数据  
                break;  
            case URI_DATA_ITEM: // 如果是单个数据项的URI  
                id = uri.getPathSegments().get(1); // 获取数据ID  
                count = db.delete(TABLE.DATA,  
                        DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs); // 从数据表删除单个项  
                deleteData = true; // 标记为删除了数据  
                break;  
            default:  
                throw new IllegalArgumentException("Unknown URI " + uri); // 如果URI未知，抛出异常  
        }  
          
        // 如果删除了数据，通知监听器  
        if (count > 0) {  
            if (deleteData) {  
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null); // 通知笔记URI的监听器  
            }  
            getContext().getContentResolver().notifyChange(uri, null); // 通知操作URI的监听器  
        }  
          
        return count; // 返回删除的行数  
    }  
  
    // 更新数据库中的数据  
    @Override  
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {  
        int count = 0;  
        String id = null;  
        SQLiteDatabase db = mHelper.getWritableDatabase();  
        boolean updateData = false;  
          
        // 根据URI匹配器的结果决定更新哪个表  
        switch (mMatcher.match(uri)) {  
            case URI_NOTE: // 如果是笔记URI  
                increaseNoteVersion(-1, selection, selectionArgs); // 更新笔记版本（特殊逻辑）  
                count = db.update(TABLE.NOTE, values, selection, selectionArgs); // 更新笔记表  
                break;  
            case URI_NOTE_ITEM: // 如果是单个笔记项的URI  
                id = uri.getPathSegments().get(1); // 获取笔记ID  
                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs); // 更新笔记版本（特殊逻辑）  
                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id  
                        + parseSelection(selection), selectionArgs); // 更新笔记表中的单个项  
                break;  
            case URI_DATA: // 如果是数据URI  
                count = db.update(TABLE.DATA, values, selection, selectionArgs); // 更新数据表  
                updateData = true; // 标记为更新了数据  
                break;  
            case URI_DATA_ITEM: // 如果是单个数据项的URI  
                id = uri.getPathSegments().get(1); // 获取数据ID  
                count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id  
                        + parseSelection(selection), selectionArgs); // 更新数据表中的单个项  
                updateData = true; // 标记为更新了数据  
                break;  
            default:  
                throw new IllegalArgumentException("Unknown URI " + uri); // 如果URI未知，抛出异常  
        }  
          
        // 如果更新了数据，通知监听器  
        if (count > 0) {  
            if (updateData) {  
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null); // 通知笔记URI的监听器  
            }  
            getContext().getContentResolver().notifyChange(uri, null); // 通知操作URI的监听器  
        }  
          
        return count; // 返回更新的行数  
    }  
  
    // 解析额外的筛选条件字符串  
    private String parseSelection(String selection) {  
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");  
    }  
  
    // 增加笔记的版本号  
    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 "); // 更新版本号  
  
        // 构建WHERE子句  
        if (id > 0 || !TextUtils.isEmpty(selection)) {  
            sql.append(" WHERE ");  
        }  
        if (id > 0) {  
            sql.append(NoteColumns.ID + "=" + String.valueOf(id)); // 根据ID更新  
        }  
        if (!TextUtils.isEmpty(selection)) {  
            String selectString = id > 0 ? parseSelection(selection) : selection; // 解析筛选条件  
            for (String args : selectionArgs) {  
                selectString = selectString.replaceFirst("\\?", args); // 替换占位符  
            }  
            sql.append(selectString); // 添加筛选条件  
        }  
  
        // 执行SQL语句  
        mHelper.getWritableDatabase().execSQL(sql.toString());  
    }  
  
    // 获取URI的类型（未实现）  
    @Override  
    public String getType(Uri uri) {  
        return null; // 此处应返回MIME类型，但代码未实现  
    }  
  
    // 其他方法和成员变量（如mMatcher, TABLE, mHelper等）已省略，假设它们在其他地方定义。