XiaoMiNotes/src/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;

/**
 * NotesProvider 类 - 便签应用的ContentProvider
 *
 * 功能：为便签应用提供数据访问接口，通过ContentProvider机制实现数据共享
 * 继承自ContentProvider，实现对note表和data表的CRUD操作，并支持搜索功能
 */
public class NotesProvider extends ContentProvider {
    private static final UriMatcher mMatcher; // URI匹配器，用于匹配不同的URI请求

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

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

    // URI匹配常量定义
    private static final int URI_NOTE            = 1; // 匹配note表所有记录
    private static final int URI_NOTE_ITEM       = 2; // 匹配note表单条记录
    private static final int URI_DATA            = 3; // 匹配data表所有记录
    private static final int URI_DATA_ITEM       = 4; // 匹配data表单条记录
    private static final int URI_SEARCH          = 5; // 匹配搜索请求
    private static final int URI_SEARCH_SUGGEST  = 6; // 匹配搜索建议请求

    // 静态初始化块：初始化URI匹配器，添加各种URI模式
    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);
    }

    /**
     * 搜索投影字段定义：
     * x'0A' 表示SQLite中的换行符'\n'
     * 对于搜索结果中的标题和内容，我们将修剪'\n'和空格以显示更多信息
     */
    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;

    // 便签片段搜索查询语句
    private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
            + " FROM " + TABLE.NOTE
            + " WHERE " + NoteColumns.SNIPPET + " LIKE ?" // 模糊匹配搜索条件
            + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER // 排除回收站中的便签
            + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE; // 只搜索普通便签类型

    /**
     * ContentProvider创建时调用，初始化数据库帮助类
     * @return true表示初始化成功
     */
    @Override
    public boolean onCreate() {
        mHelper = NotesDatabaseHelper.getInstance(getContext());
        return true;
    }

    /**
     * 查询方法，根据URI匹配不同的查询逻辑
     * @param uri 请求的URI
     * @param projection 要返回的列
     * @param selection 查询条件
     * @param selectionArgs 查询参数
     * @param sortOrder 排序方式
     * @return 查询结果的Cursor对象
     */
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
                        String sortOrder) {
        Cursor c = null;
        SQLiteDatabase db = mHelper.getReadableDatabase();
        String id = null;
        switch (mMatcher.match(uri)) {
            case URI_NOTE: // 查询note表所有记录
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_NOTE_ITEM: // 查询note表单条记录
                id = uri.getPathSegments().get(1); // 从URI路径段中获取ID
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_DATA: // 查询data表所有记录
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_DATA_ITEM: // 查询data表单条记录
                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");
                }

                String searchString = null;
                // 根据URI类型获取搜索字符串
                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
                    if (uri.getPathSegments().size() > 1) {
                        searchString = uri.getPathSegments().get(1);
                    }
                } else {
                    searchString = uri.getQueryParameter("pattern"); // 从查询参数获取搜索模式
                }

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

                try {
                    searchString = String.format("%%%s%%", searchString); // 添加通配符进行模糊匹配
                    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，以便在数据变化时能够通知观察者
        if (c != null) {
            c.setNotificationUri(getContext().getContentResolver(), uri);
        }
        return c;
    }

    /**
     * 插入数据方法
     * @param uri 请求的URI
     * @param values 要插入的数据
     * @return 插入数据的新URI
     */
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = mHelper.getWritableDatabase();
        long dataId = 0, noteId = 0, insertedId = 0;
        switch (mMatcher.match(uri)) {
            case URI_NOTE: // 插入note表记录
                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
                break;
            case URI_DATA: // 插入data表记录
                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note URI的数据变化
        if (noteId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
        }

        // 通知data URI的数据变化
        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);
    }

    /**
     * 删除数据方法
     * @param uri 请求的URI
     * @param selection 删除条件
     * @param selectionArgs 删除参数
     * @return 删除的记录数
     */
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean deleteData = false; // 标记是否删除data表数据
        switch (mMatcher.match(uri)) {
            case URI_NOTE: // 删除note表记录（系统文件夹不允许删除）
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
                count = db.delete(TABLE.NOTE, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM: // 删除note表单条记录
                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; // 系统文件夹不删除
                }
                count = db.delete(TABLE.NOTE,
                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA: // 删除data表记录
                count = db.delete(TABLE.DATA, selection, selectionArgs);
                deleteData = true;
                break;
            case URI_DATA_ITEM: // 删除data表单条记录
                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);
        }
        // 如果删除了记录，通知数据变化
        if (count > 0) {
            if (deleteData) {
                // 删除data表数据时需要通知note URI
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    /**
     * 更新数据方法
     * @param uri 请求的URI
     * @param values 更新的数据
     * @param selection 更新条件
     * @param selectionArgs 更新参数
     * @return 更新的记录数
     */
    @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; // 标记是否更新data表数据
        switch (mMatcher.match(uri)) {
            case URI_NOTE: // 更新note表记录
                increaseNoteVersion(-1, selection, selectionArgs); // 增加版本号
                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM: // 更新note表单条记录
                id = uri.getPathSegments().get(1);
                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs); // 增加版本号
                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA: // 更新data表记录
                count = db.update(TABLE.DATA, values, selection, selectionArgs);
                updateData = true;
                break;
            case URI_DATA_ITEM: // 更新data表单条记录
                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);
        }

        // 如果更新了记录，通知数据变化
        if (count > 0) {
            if (updateData) {
                // 更新data表数据时需要通知note URI
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    /**
     * 解析选择条件，将传入的条件转换为AND连接的条件
     * @param selection 原始选择条件
     * @return 解析后的选择条件字符串
     */
    private String parseSelection(String selection) {
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
    }

    /**
     * 增加便签版本号
     * @param id 便签ID（大于0）或-1表示更新所有匹配的记录
     * @param selection 更新条件
     * @param selectionArgs 更新参数
     */
    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 "); // 版本号加1

        // 构建WHERE子句
        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URI对应的MIME类型（暂未实现）
     * @param uri 请求的URI
     * @return MIME类型字符串
     */
    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }
}