hl-notes/java/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.
 */

/**
 * 文件: NotesProvider.java
 * 描述: 便签应用的内容提供者，负责管理便签数据的访问
 * 作用: 为应用程序和其他应用提供便签数据的统一访问接口，实现数据的增删改查操作
 */
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;

/**
 * 便签内容提供者类
 * 
 * 继承自ContentProvider，负责处理对便签数据的访问请求
 * 实现了标准的CRUD操作（创建、读取、更新、删除）
 * 支持便签搜索功能
 */
public class NotesProvider extends ContentProvider {
    /** URI匹配器，用于匹配请求的URI类型 */
    private static final UriMatcher mMatcher;

    /** 数据库帮助类实例 */
    private NotesDatabaseHelper mHelper;

    /** 日志标签 */
    private static final String TAG = "NotesProvider";

    /** 便签表URI类型 */
    private static final int URI_NOTE            = 1;
    /** 单个便签项URI类型 */
    private static final int URI_NOTE_ITEM       = 2;
    /** 数据表URI类型 */
    private static final int URI_DATA            = 3;
    /** 单个数据项URI类型 */
    private static final int URI_DATA_ITEM       = 4;

    /** 搜索URI类型 */
    private static final int URI_SEARCH          = 5;
    /** 搜索建议URI类型 */
    private static final int URI_SEARCH_SUGGEST  = 6;

    // 静态初始化块，配置URI匹配器
    static {
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 添加各种URI匹配规则
        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);
    }

    /**
     * 搜索结果的投影列
     * x'0A'表示SQLite中的'\n'字符。为了在搜索结果中显示更多信息，
     * 我们会删除标题和内容中的'\n'和空格。
     */
    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;

    /**
     * 便签片段搜索查询SQL
     * 用于搜索便签内容，排除回收站中的便签和非便签类型的项目
     */
    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;

    /**
     * 内容提供者初始化
     * 
     * @return 初始化是否成功
     */
    @Override
    public boolean onCreate() {
        // 获取数据库帮助类实例
        mHelper = NotesDatabaseHelper.getInstance(getContext());
        return true;
    }

    /**
     * 查询数据
     * 
     * @param uri 请求的URI
     * @param projection 要返回的列
     * @param selection 查询条件
     * @param selectionArgs 查询条件参数
     * @param sortOrder 排序方式
     * @return 查询结果游标
     */
    @Override
    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;
        
        // 根据URI类型执行不同的查询操作
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 查询便签表
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_NOTE_ITEM:
                // 查询单个便签项
                id = uri.getPathSegments().get(1);
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_DATA:
                // 查询数据表
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_DATA_ITEM:
                // 查询单个数据项
                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:
                // 处理搜索和搜索建议请求
                if (sortOrder != null || projection != null) {
                    throw new IllegalArgumentException(
                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
                }

                // 获取搜索字符串
                String searchString = null;
                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
                    if (uri.getPathSegments().size() > 1) {
                        searchString = uri.getPathSegments().get(1);
                    }
                } else {
                    searchString = uri.getQueryParameter("pattern");
                }

                // 如果搜索字符串为空，则返回null
                if (TextUtils.isEmpty(searchString)) {
                    return null;
                }

                // 执行搜索查询
                try {
                    searchString = String.format("%%%s%%", searchString); // 添加通配符以进行模糊匹配
                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
                            new String[] { searchString });
                } catch (IllegalStateException ex) {
                    Log.e(TAG, "got exception: " + ex.toString());
                }
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        
        // 设置通知URI，当数据变化时通知观察者
        if (c != null) {
            c.setNotificationUri(getContext().getContentResolver(), uri);
        }
        return c;
    }

    /**
     * 插入数据
     * 
     * @param uri 请求的URI
     * @param values 要插入的值
     * @return 插入后的URI
     */
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // 获取可写数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        long dataId = 0, noteId = 0, insertedId = 0;
        
        // 根据URI类型执行不同的插入操作
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 插入便签
                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
                break;
            case URI_DATA:
                // 插入数据
                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);
        }
        
        // 通知便签URI的观察者
        if (noteId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
        }

        // 通知数据URI的观察者
        if (dataId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
        }

        return ContentUris.withAppendedId(uri, insertedId);
    }

    /**
     * 删除数据
     * 
     * @param uri 请求的URI
     * @param selection 删除条件
     * @param selectionArgs 删除条件参数
     * @return 删除的行数
     */
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        // 获取可写数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean deleteData = false;
        
        // 根据URI类型执行不同的删除操作
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 删除便签，ID必须大于0（系统文件夹ID小于等于0）
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
                count = db.delete(TABLE.NOTE, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM:
                // 删除单个便签项
                id = uri.getPathSegments().get(1);
                /**
                 * ID小于0的是系统文件夹，不允许删除
                 */
                long noteId = Long.valueOf(id);
                if (noteId <= 0) {
                    break;
                }
                count = db.delete(TABLE.NOTE,
                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA:
                // 删除数据
                count = db.delete(TABLE.DATA, selection, selectionArgs);
                deleteData = true;
                break;
            case URI_DATA_ITEM:
                // 删除单个数据项
                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);
        }
        
        // 如果有删除操作，通知观察者
        if (count > 0) {
            if (deleteData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    /**
     * 更新数据
     * 
     * @param uri 请求的URI
     * @param values 要更新的值
     * @param selection 更新条件
     * @param selectionArgs 更新条件参数
     * @return 更新的行数
     */
    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        // 获取可写数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean updateData = false;
        
        // 根据URI类型执行不同的更新操作
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 更新便签表
                increaseNoteVersion(-1, selection, selectionArgs); // 增加便签版本号
                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM:
                // 更新单个便签项
                id = uri.getPathSegments().get(1);
                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs); // 增加便签版本号
                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA:
                // 更新数据表
                count = db.update(TABLE.DATA, values, selection, selectionArgs);
                updateData = true;
                break;
            case URI_DATA_ITEM:
                // 更新单个数据项
                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);
        }

        // 如果有更新操作，通知观察者
        if (count > 0) {
            if (updateData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    /**
     * 解析选择条件
     * 将额外的选择条件添加到现有条件中
     * 
     * @param selection 选择条件
     * @return 解析后的选择条件
     */
    private String parseSelection(String selection) {
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
    }

    /**
     * 增加便签版本号
     * 当便签内容更新时，增加版本号以便于同步
     * 
     * @param id 便签ID，如果为-1则使用selection和selectionArgs
     * @param selection 选择条件
     * @param selectionArgs 选择条件参数
     */
    private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
        // 构建更新版本号的SQL语句
        StringBuilder sql = new StringBuilder(120);
        sql.append("UPDATE ");
        sql.append(TABLE.NOTE);
        sql.append(" SET ");
        sql.append(NoteColumns.VERSION);
        sql.append("=" + NoteColumns.VERSION + "+1 ");

        // 添加WHERE条件
        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;
            // 替换参数占位符
            for (String args : selectionArgs) {
                selectString = selectString.replaceFirst("\\?", args);
            }
            sql.append(selectString);
        }

        // 执行SQL语句
        mHelper.getWritableDatabase().execSQL(sql.toString());
    }

    /**
     * 获取内容类型
     * 
     * @param uri 请求的URI
     * @return 内容类型
     */
    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }
}