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/*
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* Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package net.micode.notes.data;
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import android.app.SearchManager;
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import android.content.ContentProvider;
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import android.content.ContentUris;
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import android.content.ContentValues;
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import android.content.Intent;
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import android.content.UriMatcher;
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import android.database.Cursor;
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import android.database.sqlite.SQLiteDatabase;
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import android.net.Uri;
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import android.text.TextUtils;
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import android.util.Log;
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import net.micode.notes.R;
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import net.micode.notes.data.Notes.DataColumns;
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import net.micode.notes.data.Notes.NoteColumns;
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import net.micode.notes.data.NotesDatabaseHelper.TABLE;
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public class NotesProvider extends ContentProvider {
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//初始化静态成员变量
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private static final UriMatcher mMatcher;//UriMatcher用于匹配URI，并根据定义的规则进行操作
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private NotesDatabaseHelper mHelper;
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private static final String TAG = "NotesProvider";
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private static final int URI_NOTE = 1;
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private static final int URI_NOTE_ITEM = 2;
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private static final int URI_DATA = 3;
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private static final int URI_DATA_ITEM = 4;
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private static final int URI_SEARCH = 5;
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private static final int URI_SEARCH_SUGGEST = 6;
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//静态初始化块，用于在类加载时执行一些静态的初始化操作
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static {
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mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
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mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
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mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM);
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mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA);
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mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM);
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mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH);
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mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST);
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mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST);
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}//为NotesProvider中的不同URI模式分配匹配码，以便在ContentProvider中根据URI执行相应的操作
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/**
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* x'0A' represents the '\n' character in sqlite. For title and content in the search result,
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* we will trim '\n' and white space in order to show more information.
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*在SQLite中，十六进制表示法x'0A'代表换行符'\n'。在搜索结果中，针对标题和内容，开发人员会去除换行符'\n'和空格，以便在展示信息时能够呈现更多内容，而不受这些额外字符的干扰
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*/
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//NOTES_SEARCH_PROJECTION这是一个字符串常量，用于定义搜索结果的投影，即要从数据库中检索哪些列的数据.
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private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + ","
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+ NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + ","
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+ "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + ","
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+ "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + ","
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+ R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + ","
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+ "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + ","
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+ "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA;
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//NOTES_SNIPPET_SEARCH_QUERY是一个字符串常量，表示执行搜索时使用的SQL查询
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private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
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+ " FROM " + TABLE.NOTE
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+ " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
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+ " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
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+ " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
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//一个重写的方法，覆盖了ContentProvider类中的onCreate()方法
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@Override//这是一个注解，表示这个方法是对父类（ContentProvider）中的方法进行重写
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public boolean onCreate() {
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mHelper = NotesDatabaseHelper.getInstance(getContext());
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return true;
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}
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//query方法根据提供的Uri执行数据库查询操作，从而提供所需的数据。它支持对不同表的查询、对单个记录的查询以及搜索功能
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@Override
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public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
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String sortOrder)
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//query方法的声明，它接收一个Uri对象、投影、选择条件、选择参数和排序顺序作为参数，并返回一个Cursor对象
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{
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Cursor c = null;
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SQLiteDatabase db = mHelper.getReadableDatabase();
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String id = null;
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switch (mMatcher.match(uri)) //UriMatcher来匹配Uri并执行相应的操作
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{
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case URI_NOTE:
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c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
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sortOrder);
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break;
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case URI_NOTE_ITEM:
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id = uri.getPathSegments().get(1);
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c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
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+ parseSelection(selection), selectionArgs, null, null, sortOrder);
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break;
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case URI_DATA:
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c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
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sortOrder);
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break;
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case URI_DATA_ITEM:
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id = uri.getPathSegments().get(1);
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c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id
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+ parseSelection(selection), selectionArgs, null, null, sortOrder);
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break;
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case URI_SEARCH:
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case URI_SEARCH_SUGGEST:
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if (sortOrder != null || projection != null) {
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throw new IllegalArgumentException(
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"do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
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}
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String searchString = null;
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if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
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if (uri.getPathSegments().size() > 1) {
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searchString = uri.getPathSegments().get(1);
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}
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} else {
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searchString = uri.getQueryParameter("pattern");
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}
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if (TextUtils.isEmpty(searchString)) {
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return null;
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}
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try {
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searchString = String.format("%%%s%%", searchString);
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c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
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new String[] { searchString });
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} catch (IllegalStateException ex) {
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Log.e(TAG, "got exception: " + ex.toString());
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}
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break;
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default:
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throw new IllegalArgumentException("Unknown URI " + uri);
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}
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if (c != null) {
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c.setNotificationUri(getContext().getContentResolver(), uri);
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}
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return c;
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}
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//这是一个用于处理数据插入的方法。根据提供的URI，它会将内容值插入相应的数据库表中。如果插入的是笔记数据，它会将笔记ID返回；如果插入的是数据项，它会检查数据是否包含笔记ID，并将其返回。最后，它会通知相关URI的观察者，以便更新UI
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@Override
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public Uri insert(Uri uri, ContentValues values) {
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SQLiteDatabase db = mHelper.getWritableDatabase();
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long dataId = 0, noteId = 0, insertedId = 0;
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switch (mMatcher.match(uri)) {
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case URI_NOTE:
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// 插入笔记数据
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insertedId = noteId = db.insert(TABLE.NOTE, null, values);
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break;
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case URI_DATA:
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// 插入数据项
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if (values.containsKey(DataColumns.NOTE_ID)) {
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// 如果数据项包含笔记ID，则获取它
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noteId = values.getAsLong(DataColumns.NOTE_ID);
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} else {
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// 如果数据项不包含笔记ID，则记录错误并打印相关数据
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Log.d(TAG, "Wrong data format without note id:" + values.toString());
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}
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insertedId = dataId = db.insert(TABLE.DATA, null, values);
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break;
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default:
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// 对于未知的URI，抛出异常
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throw new IllegalArgumentException("Unknown URI " + uri);
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}
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// Notify the note uri
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// 通知笔记URI
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if (noteId > 0) {
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getContext().getContentResolver().notifyChange(
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ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
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}
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// Notify the data uri
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// 通知数据URI
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if (dataId > 0) {
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getContext().getContentResolver().notifyChange(
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ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
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}
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// 返回插入的URI
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return ContentUris.withAppendedId(uri, insertedId);
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}
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@Override
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public int delete(Uri uri, String selection, String[] selectionArgs) {
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int count = 0;
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String id = null;
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SQLiteDatabase db = mHelper.getWritableDatabase();
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boolean deleteData = false;
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switch (mMatcher.match(uri)) {
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case URI_NOTE:
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// 删除操作的条件，确保ID大于0
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selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
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count = db.delete(TABLE.NOTE, selection, selectionArgs);
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break;
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case URI_NOTE_ITEM:
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id = uri.getPathSegments().get(1);
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/**
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* ID that smaller than 0 is system folder which is not allowed to
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*ID小于0的是系统文件夹，不能放入回收站
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* trash
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*/
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long noteId = Long.valueOf(id);
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if (noteId <= 0) {
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break;
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}
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// 根据指定ID执行删除操作，并根据传入的条件进行筛选
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count = db.delete(TABLE.NOTE,
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NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
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break;
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case URI_DATA:
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// 删除数据表中的数据
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count = db.delete(TABLE.DATA, selection, selectionArgs);
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deleteData = true;
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break;
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case URI_DATA_ITEM:
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id = uri.getPathSegments().get(1);
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// 根据指定ID执行删除操作，并根据传入的条件进行筛选
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count = db.delete(TABLE.DATA,
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DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
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deleteData = true;
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break;
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default:
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// 未知的URI抛出异常
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throw new IllegalArgumentException("Unknown URI " + uri);
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}
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// 如果有数据被删除
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if (count > 0) {
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// 如果删除的是数据表中的数据，则通知内容解析器数据已更改
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if (deleteData) {
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getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
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}
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// 通知内容解析器指定URI的数据已更改
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getContext().getContentResolver().notifyChange(uri, null);
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}
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// 返回受影响的行数
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return count;
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}
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//根据指定条件更新数据库中的数据，根据uri的不同匹配到相应的表和记录，并进行更新操作
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@Override
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public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
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int count = 0;
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String id = null;
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SQLiteDatabase db = mHelper.getWritableDatabase();
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boolean updateData = false;
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switch (mMatcher.match(uri)) {
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case URI_NOTE:
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// 增加笔记版本
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increaseNoteVersion(-1, selection, selectionArgs);
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// 执行更新操作，并获取受影响的行数
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count = db.update(TABLE.NOTE, values, selection, selectionArgs);
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break;
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case URI_NOTE_ITEM:
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// 获取URI中的ID
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id = uri.getPathSegments().get(1);
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// 增加指定笔记ID的版本
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increaseNoteVersion(Long.valueOf(id), selection, selectionArgs);
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// 根据指定ID执行更新操作，并根据传入的条件进行筛选
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count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
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+ parseSelection(selection), selectionArgs);
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break;
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case URI_DATA:
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// 更新数据表中的数据
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count = db.update(TABLE.DATA, values, selection, selectionArgs);
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updateData = true;
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break;
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case URI_DATA_ITEM:
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// 获取URI中的ID
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id = uri.getPathSegments().get(1);
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// 根据指定ID执行更新操作，并根据传入的条件进行筛选
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count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id
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+ parseSelection(selection), selectionArgs);
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updateData = true;
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break;
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default:
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// 未知的URI抛出异常
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throw new IllegalArgumentException("Unknown URI " + uri);
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}
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// 如果有数据被更新
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if (count > 0) {
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if (updateData) {
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// 如果更新的是数据表中的数据，则通知内容解析器数据已更改
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getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
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}
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// 通知内容解析器指定URI的数据已更改
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getContext().getContentResolver().notifyChange(uri, null);
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}
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// 返回受影响的行数
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return count;
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}
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private String parseSelection(String selection) {
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return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
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}
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//用于管理和操作笔记数据的版本号
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private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
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// 构建SQL语句
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StringBuilder sql = new StringBuilder(120);
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sql.append("UPDATE ");// 更新操作
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sql.append(TABLE.NOTE);// 要更新的表名
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sql.append(" SET ");
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sql.append(NoteColumns.VERSION);// 版本号字段
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sql.append("=" + NoteColumns.VERSION + "+1 ");// 版本号自增1
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// 如果存在ID或者选择条件非空，则添加WHERE子句
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if (id > 0 || !TextUtils.isEmpty(selection)) {
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sql.append(" WHERE ");
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}
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// 如果存在ID，添加ID等于指定ID的条件
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if (id > 0) {
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sql.append(NoteColumns.ID + "=" + String.valueOf(id));
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}
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// 如果选择条件非空，解析选择条件并添加到SQL语句中
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if (!TextUtils.isEmpty(selection)) {
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String selectString = id > 0 ? parseSelection(selection) : selection;
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for (String args : selectionArgs) {
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selectString = selectString.replaceFirst("\\?", args);
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}
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sql.append(selectString);
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}
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// 执行SQL语句，更新数据库中笔记版本号
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mHelper.getWritableDatabase().execSQL(sql.toString());
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}
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@Override
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public String getType(Uri uri) {
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// TODO Auto-generated method stub
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return null;
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}
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}
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