xiaomi/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;


public class NotesProvider extends ContentProvider {
    // 定义UriMatcher对象
    private static final UriMatcher mMatcher;

    // 定义NotesDatabaseHelper对象
    private NotesDatabaseHelper mHelper;

    // 定义TAG常量
    private static final String TAG = "NotesProvider";

    // 定义URI常量
    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;

    // 静态代码块，初始化UriMatcher对象
    static {
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 添加URI匹配规则
        mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
// 添加URI匹配规则
        mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM); // 添加匹配规则，匹配以"note/"开头的URI，后面跟一个数字，匹配结果为URI_NOTE_ITEM
        mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA); // 添加匹配规则，匹配以"data/"开头的URI，匹配结果为URI_DATA
        mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM); // 添加匹配规则，匹配以"data/"开头的URI，后面跟一个数字，匹配结果为URI_DATA_ITEM
        mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH); // 添加匹配规则，匹配以"search/"开头的URI，匹配结果为URI_SEARCH
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST); // 添加匹配规则，匹配以SearchManager.SUGGEST_URI_PATH_QUERY开头的URI，匹配结果为URI_SEARCH_SUGGEST
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST); // 添加匹配规则，匹配以SearchManager.SUGGEST_URI_PATH_QUERY开头的URI，后面跟任意字符，匹配结果为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.
     */
// 定义搜索结果的投影，包括ID、文本1、文本2、图标1、意图动作和数据类型
    private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + ","
        + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + "," // 将NoteColumns.ID作为SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + "," // 将NoteColumns.SNIPPET中的换行符替换为空，并作为SearchManager.SUGGEST_COLUMN_TEXT_1
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + "," // 将NoteColumns.SNIPPET中的换行符替换为空，并作为SearchManager.SUGGEST_COLUMN_TEXT_2
        + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + "," // 将R.drawable.search_result作为SearchManager.SUGGEST_COLUMN_ICON_1
        + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + "," // 将Intent.ACTION_VIEW作为SearchManager.SUGGEST_COLUMN_INTENT_ACTION
        + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA; // 将Notes.TextNote.CONTENT_TYPE作为SearchManager.SUGGEST_COLUMN_INTENT_DATA

// 定义一个静态字符串变量，用于存储查询语句
    private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
        // 查询Note表中的数据
        + " FROM " + TABLE.NOTE
        // 查询条件：NoteColumns.SNIPPET字段中包含指定字符串
        + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
        // 查询条件：NoteColumns.PARENT_ID字段不等于Notes.ID_TRASH_FOLER
        + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
        // 查询条件：NoteColumns.TYPE字段等于Notes.TYPE_NOTE
        + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;

    @Override
    public boolean onCreate() {
        // 获取NotesDatabaseHelper的实例
        mHelper = NotesDatabaseHelper.getInstance(getContext());
        // 返回true，表示数据库创建成功
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        // 根据传入的uri，查询数据库中的数据
        Cursor c = null;
        // 获取可读的数据库
        SQLiteDatabase db = mHelper.getReadableDatabase();
        // 获取uri中的id
        String id = null;
        // 根据uri匹配查询类型
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 查询note表中的数据
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            // 查询URI_NOTE_ITEM类型的URI
            case URI_NOTE_ITEM:
                // 获取URI的路径段，获取第二个路径段作为id
                id = uri.getPathSegments().get(1);
                // 查询NOTE表，根据id和selection条件查询，返回结果集
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            // 查询URI_DATA类型的URI
            case URI_DATA:
                // 查询DATA表，根据selection条件查询，返回结果集
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            // 查询URI_DATA_ITEM类型的URI
            case URI_DATA_ITEM:
                // 获取URI的路径段，获取第二个路径段作为id
                id = uri.getPathSegments().get(1);
                // 查询DATA表，根据id和selection条件查询，返回结果集
                c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
// 如果URI是URI_SEARCH或URI_SEARCH_SUGGEST
            case URI_SEARCH:
            case URI_SEARCH_SUGGEST:
                // 如果sortOrder或projection不为空
                if (sortOrder != null || projection != null) {
                    // 抛出异常，不允许指定sortOrder、selection、selectionArgs或projection
                    throw new IllegalArgumentException(
                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
                }

 // 定义一个字符串变量，用于存储搜索字符串
                String searchString = null;
 // 如果匹配到的URI是URI_SEARCH_SUGGEST
                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
     // 如果URI的路径段大于1
                    if (uri.getPathSegments().size() > 1) {
         // 将路径段的第二个元素赋值给searchString
                        searchString = uri.getPathSegments().get(1);
                    }
                } else {
     // 否则，将URI的查询参数中名为"pattern"的值赋值给searchString
                    searchString = uri.getQueryParameter("pattern");
                }

// 判断搜索字符串是否为空
                if (TextUtils.isEmpty(searchString)) {
                    // 如果为空，则返回null
                    return null;
                }

// 尝试执行以下代码块
                try {
                    // 将搜索字符串格式化为包含通配符的字符串
                    searchString = String.format("%%%s%%", searchString);
                    // 执行数据库查询，返回结果集
                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
                            new String[] { searchString });
                } catch (IllegalStateException ex) {
                    // 如果发生异常，则打印错误日志
                    Log.e(TAG, "got exception: " + ex.toString());
                }
// 结束switch语句
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        // 如果c不为空，则设置通知URI
        if (c != null) {
            c.setNotificationUri(getContext().getContentResolver(), uri);
        }
        // 返回c
        return c;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // 获取可写的数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        // 定义变量，用于存储插入的数据ID
        long dataId = 0, noteId = 0, insertedId = 0;
        // 根据传入的URI匹配对应的操作
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 插入数据，并返回插入的数据ID
                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
                break;
            case URI_DATA:
                // 如果values中包含DataColumns.NOTE_ID，则获取其值并赋给noteId
                if (values.containsKey(DataColumns.NOTE_ID)) {
                    noteId = values.getAsLong(DataColumns.NOTE_ID);
                } else {
                    // 否则，输出错误日志
                    Log.d(TAG, "Wrong data format without note id:" + values.toString());
                }
                // 将values插入到TABLE.DATA表中，并获取插入的id
                insertedId = dataId = db.insert(TABLE.DATA, null, values);
                break;
            default:
                // 如果uri不匹配，则抛出异常
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        // Notify the note uri
 // 如果noteId大于0，则通知ContentResolver，有数据发生变化
        if (noteId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
        }

        // Notify the data uri
 // 如果dataId大于0，则通知ContentResolver数据已更改
        if (dataId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
        }

        // 返回插入的ID
        return ContentUris.withAppendedId(uri, insertedId);
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // 删除数据
        int count = 0;
        // 获取要删除的数据的id
        String id = null;
        // 获取可写的数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        // 标记是否删除数据
        boolean deleteData = false;
        switch (mMatcher.match(uri)) {
            case URI_NOTE:
                // 添加查询条件，删除ID大于0的记录
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
                count = db.delete(TABLE.NOTE, selection, selectionArgs);
                break;
            case URI_NOTE_ITEM:
                // 获取URI中的ID
                id = uri.getPathSegments().get(1);
                /**
                 * ID that smaller than 0 is system folder which is not allowed to
                 * trash
                 */
// 将id转换为long类型
                long noteId = Long.valueOf(id);
// 如果noteId小于等于0，则跳出循环
                if (noteId <= 0) {
                    break;
                }
// 删除指定ID的NOTE表中的数据
                count = db.delete(TABLE.NOTE,
                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                break;
// 删除指定URI的DATA表中的数据
            case URI_DATA:
                count = db.delete(TABLE.DATA, selection, selectionArgs);
                deleteData = true;
                break;
            case URI_DATA_ITEM:
                // 获取URI路径中的ID
                id = uri.getPathSegments().get(1);
                // 删除指定ID的数据
                count = db.delete(TABLE.DATA,
                        DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
                // 标记删除数据
                deleteData = true;
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        // 如果删除数据，则通知ContentResolver数据已更改
        if (count > 0) {
            if (deleteData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            // 通知ContentResolver数据已更改
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    @Override
    // 重写update方法，用于更新数据库中的数据
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        // 定义一个计数器，用于记录更新的数据条数
        int count = 0;
        // 定义一个字符串，用于存储要更新的数据的id
        String id = null;
        // 获取可写的数据库
        SQLiteDatabase db = mHelper.getWritableDatabase();
        // 定义一个布尔值，用于判断是否更新了数据
        boolean updateData = false;
// 根据uri匹配的结果，执行相应的操作
        switch (mMatcher.match(uri)) {
    // 如果uri匹配的是URI_NOTE，则执行以下操作
            case URI_NOTE:
        // 将note的版本号减1
                increaseNoteVersion(-1, selection, selectionArgs);
        // 更新数据库中的note表，将values中的数据更新到满足selection和selectionArgs的记录中
                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
                break;
// 根据URI_NOTE_ITEM的值，获取路径中的第二个参数作为id
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1);
// 根据id，selection和selectionArgs，增加Note的版本号
                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs);
// 根据id，values，selection和selectionArgs，更新Note表中的数据，并返回更新的行数
                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                break;
            case URI_DATA:
                // 更新数据表中的数据
                count = db.update(TABLE.DATA, values, selection, selectionArgs);
                // 标记更新数据
                updateData = true;
                break;
            case URI_DATA_ITEM:
                // 获取要更新的数据的id
                id = uri.getPathSegments().get(1);
                // 更新数据表中的数据
                count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs);
                // 标记更新数据
                updateData = true;
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }

        // 如果count大于0，则通知ContentResolver更新数据
        if (count > 0) {
            // 如果updateData为true，则通知ContentResolver更新Notes.CONTENT_NOTE_URI
            if (updateData) {
                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
            }
            // 通知ContentResolver更新uri
            getContext().getContentResolver().notifyChange(uri, null);
        }
        // 返回count
        return count;
    }

 // 解析selection字符串
    private String parseSelection(String selection) {
        // 如果selection不为空，则返回" AND (" + selection + ')'，否则返回空字符串
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
    }

    private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
        // 创建一个StringBuilder对象，用于拼接SQL语句
        StringBuilder sql = new StringBuilder(120);
        // 拼接UPDATE语句
        sql.append("UPDATE ");
        // 拼接表名
        sql.append(TABLE.NOTE);
        // 拼接SET语句
        sql.append(" SET ");
        // 拼接版本号字段
        sql.append(NoteColumns.VERSION);
        // 拼接版本号增加1的语句
        sql.append("=" + NoteColumns.VERSION + "+1 ");

// 如果id大于0或者selection不为空，则添加WHERE关键字
        if (id > 0 || !TextUtils.isEmpty(selection)) {
            sql.append(" WHERE ");
        }
// 如果id大于0，则添加id等于id的语句
        if (id > 0) {
// 拼接SQL语句，将id添加到NoteColumns.ID中
            sql.append(NoteColumns.ID + "=" + String.valueOf(id));
        }
// 如果selection不为空，则解析selection并添加到sql语句中
        if (!TextUtils.isEmpty(selection)) {
// 根据id的值，选择不同的selection字符串
            String selectString = id > 0 ? parseSelection(selection) : selection;
// 遍历selectionArgs数组，将每个元素替换selectString中的第一个问号
            for (String args : selectionArgs) {
                selectString = selectString.replaceFirst("\\?", args);
            }
// 将替换后的selectString添加到sql中
            sql.append(selectString);
        }

        mHelper.getWritableDatabase().execSQL(sql.toString());
    }

    // 根据Uri返回MIME类型
    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }

}