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NotesProvider.java
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/*
* 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;
// 导入Android框架中用于ContentProvider的相关类
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;
// 导入应用内部定义的类和接口
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;
// 继承ContentProvider类，创建NotesProvider类，用于管理笔记数据
public class NotesProvider extends ContentProvider {
// Uri匹配器，用于识别不同的URI路径
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，用于Log日志输出
private static final String TAG = "NotesProvider";
// 定义不同的URI代码，用于匹配不同的URI路径
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;
// 静态初始化块，初始化Uri匹配器
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);
}
// 定义搜索结果的投影，包括ID、摘要等信息
/**
* x'0A'代表sqlite中的'\n'字符。为了在搜索结果中显示更多信息，
* 我们将截取标题和内容中的'\n'和空白。
*/
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;
// 定义笔记摘要搜索查询
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;
// onCreate方法，初始化数据库帮助类实例
@Override
public boolean onCreate() {
mHelper = NotesDatabaseHelper.getInstance(getContext());
return true;
}
// query方法，处理查询请求
@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匹配结果，执行不同的查询操作
switch (mMatcher.match(uri)) {
case URI_NOTE:
// 查询笔记表
c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
sortOrder);
break;
case URI_NOTE_ITEM:
// 查询单个笔记项
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:
// 处理搜索请求
if (sortOrder != null || projection != null) {
throw new IllegalArgumentException(
"do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
}
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");
}
if (TextUtils.isEmpty(searchString)) {
return null;
}
try {
searchString = String.format("%%%s%%", searchString);
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，以便在数据变化时通知外界
if (c != null) {
c.setNotificationUri(getContext().getContentResolver(), uri);
}
return c;
}
}
以下是对代码中关键部分的注释：
java
/**
* 实现ContentProvider接口的insert方法，用于插入新的数据。
* @param uri 请求的URI，用于确定插入数据的表。
* @param values 包含要插入数据的ContentValues。
* @return 插入数据的URI，包括ID。
*/
@Override
public Uri insert(Uri uri, ContentValues values) {
// 获取可写数据库实例
SQLiteDatabase db = mHelper.getWritableDatabase();
long dataId = 0, noteId = 0, insertedId = 0;
// 使用UriMatcher匹配URI，确定插入哪个表
switch (mMatcher.match(uri)) {
case URI_NOTE:
// 插入笔记数据
insertedId = noteId = db.insert(TABLE.NOTE, null, values);
break;
case URI_DATA:
// 插入数据，如果包含笔记ID，则记录
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:
// 如果URI不匹配，则抛出异常
throw new IllegalArgumentException("Unknown URI " + uri);
}
// 如果插入笔记ID大于0，通知变化
if (noteId > 0) {
getContext().getContentResolver().notifyChange(
ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
}
// 如果插入数据ID大于0，通知变化
if (dataId > 0) {
getContext().getContentResolver().notifyChange(
ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
}
// 返回插入数据的URI
return ContentUris.withAppendedId(uri, insertedId);
}
/**
* 实现ContentProvider接口的delete方法，用于删除数据。
* @param uri 请求的URI，用于确定删除数据的表。
* @param selection 删除条件。
* @param selectionArgs 删除条件的参数。
* @return 删除的行数。
*/
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
int count = 0;
String id = null;
SQLiteDatabase db = mHelper.getWritableDatabase();
boolean deleteData = false;
// 使用UriMatcher匹配URI，确定删除哪个表
switch (mMatcher.match(uri)) {
case URI_NOTE:
// 删除笔记数据，限制删除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:
// 删除单个笔记项
id = uri.getPathSegments().get(1);
long noteId = Long.valueOf(id);
if (noteId <= 0) {
break;
}
count = db.delete(TABLE.NOTE,
NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
break;
case URI_DATA:
// 删除数据表中的记录
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:
// 如果URI不匹配，则抛出异常
throw new IllegalArgumentException("Unknown URI " + uri);
}
// 如果删除了记录，通知变化
if (count > 0) {
if (deleteData) {
getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
}
getContext().getContentResolver().notifyChange(uri, null);
}
return count;
}
/**
* 实现ContentProvider接口的update方法，用于更新数据。
* @param uri 请求的URI，用于确定更新数据的表。
* @param values 包含要更新数据的ContentValues。
* @param selection 更新条件。
* @param selectionArgs 更新条件的参数。
* @return 更新的行数。
*/
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
int count = 0;
String id = null;
SQLiteDatabase db = mHelper.getWritableDatabase();
boolean updateData = false;
// 使用UriMatcher匹配URI，确定更新哪个表
switch (mMatcher.match(uri)) {
case URI_NOTE:
// 更新笔记数据，增加版本号
increaseNoteVersion(-1, selection, selectionArgs);
count = db.update(TABLE.NOTE, values, selection, selectionArgs);
break;
case URI_NOTE_ITEM:
// 更新单个笔记项
id = uri.getPathSegments().get(1);
increaseNoteVersion(Long.valueOf(id), selection, selectionArgs);
count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
+ parseSelection(selection), selectionArgs);
break;
case URI_DATA:
// 更新数据表中的记录
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:
// 如果URI不匹配，则抛出异常
throw new IllegalArgumentException("Unknown URI " + uri);
}
// 如果更新了记录，通知变化
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，添加AND前缀。
* @param selection 选择条件。
* @return 处理后的选择条件。
*/
private String parseSelection(String selection) {
return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
}
/**
* 增加笔记的版本号。
* @param id 笔记ID，-1表示更新所有匹配的记录。
* @param selection 更新条件。
* @param selectionArgs 更新条件的参数。
*/
private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
// 构建SQL语句，增加版本号
StringBuilder sql = new StringBuilder(120);
sql.append("UPDATE ");
sql.append(TABLE.NOTE);
sql.append(" SET ");
sql.append(NoteColumns.VERSION);
sql.append("=" + NoteColumns.VERSION + "+1 ");
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;
for (String args : selectionArgs) {
selectString = selectString.replaceFirst("\\?", args);
}
sql.append(selectString);
}
// 执行SQL语句
mHelper.getWritableDatabase().execSQL(sql.toString());
}
/**
* 实现ContentProvider接口的getType方法，用于获取数据类型。
* @param uri 请求的URI。
* @return 数据类型，此方法未实现返回null。
*/
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
}
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