> 编写:[Lin-H](https://github.com/Lin-H) - 原文:[http://developer.android.com/training/search/search.html](http://developer.android.com/training/search/search.html) 有很多方法可以储存你的数据，比如储存在线上的数据库，本地的SQLite数据库，甚至是文本文件。你自己来选择最适合你应用的存储方式。本节课程会向你展示如何创建一个健壮的可以提供全文搜索的SQLite虚拟表。并从一个每行有一组单词-解释对的文件中将数据填入。 ### 创建虚拟表 虚拟表与SQLite表的运行方式类似，但虚拟表是通过回调来向内存中的对象进行读取和写入，而不是通过数据库文件。要创建一个虚拟表，首先为该表创建一个类: ~~~ public class DatabaseTable { private final DatabaseOpenHelper mDatabaseOpenHelper; public DatabaseTable(Context context) { mDatabaseOpenHelper = new DatabaseOpenHelper(context); } } ~~~ 在`DatabaseTable`类中创建一个继承[SQLiteOpenHelper](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html)的内部类。你必须重写类[SQLiteOpenHelper](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html)中定义的abstract方法，才能在必要的时候创建和更新你的数据库表。例如，下面一段代码声明了一个数据库表，用来储存字典app所需的单词。 ~~~ public class DatabaseTable { private static final String TAG = "DictionaryDatabase"; //字典的表中将要包含的列项 public static final String COL_WORD = "WORD"; public static final String COL_DEFINITION = "DEFINITION"; private static final String DATABASE_NAME = "DICTIONARY"; private static final String FTS_VIRTUAL_TABLE = "FTS"; private static final int DATABASE_VERSION = 1; private final DatabaseOpenHelper mDatabaseOpenHelper; public DatabaseTable(Context context) { mDatabaseOpenHelper = new DatabaseOpenHelper(context); } private static class DatabaseOpenHelper extends SQLiteOpenHelper { private final Context mHelperContext; private SQLiteDatabase mDatabase; private static final String FTS_TABLE_CREATE = "CREATE VIRTUAL TABLE " + FTS_VIRTUAL_TABLE + " USING fts3 (" + COL_WORD + ", " + COL_DEFINITION + ")"; DatabaseOpenHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); mHelperContext = context; } @Override public void onCreate(SQLiteDatabase db) { mDatabase = db; mDatabase.execSQL(FTS_TABLE_CREATE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS " + FTS_VIRTUAL_TABLE); onCreate(db); } } } ~~~ ### 填入虚拟表 现在，表需要数据来储存。下面的代码会向你展示如何读取一个内容为单词和解释的文本文件(位于`res/raw/definitions.txt`)，如何解析文件与如何将文件中的数据按行插入虚拟表中。为防止UI锁死这些操作会在另一条线程中执行。将下面的一段代码添加到你的`DatabaseOpenHelper`内部类中。 > **Tip**:你也可以设置一个回调来通知你的UI [activity](# "An activity represents a single screen with a user interface.")线程的完成结果。 ~~~ private void loadDictionary() { new Thread(new Runnable() { public void run() { try { loadWords(); } catch (IOException e) { throw new RuntimeException(e); } } }).start(); } private void loadWords() throws IOException { final Resources resources = mHelperContext.getResources(); InputStream inputStream = resources.openRawResource(R.raw.definitions); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); try { String line; while ((line = reader.readLine()) != null) { String[] strings = TextUtils.split(line, "-"); if (strings.length < 2) continue; long id = addWord(strings[0].trim(), strings[1].trim()); if (id < 0) { Log.e(TAG, "unable to add word: " + strings[0].trim()); } } } finally { reader.close(); } } public long addWord(String word, String definition) { ContentValues initialValues = new ContentValues(); initialValues.put(COL_WORD, word); initialValues.put(COL_DEFINITION, definition); return mDatabase.insert(FTS_VIRTUAL_TABLE, null, initialValues); } ~~~ 任何恰当的地方，都可以调用`loadDictionary()`方法向表中填入数据。一个比较好的地方是`DatabaseOpenHelper`类的[onCreate()](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html#onCreate(android.database.sqlite.SQLiteDatabase))方法中，紧随创建表之后: ~~~ @Override public void onCreate(SQLiteDatabase db) { mDatabase = db; mDatabase.execSQL(FTS_TABLE_CREATE); loadDictionary(); } ~~~ ### 搜索请求 当你的虚拟表创建好并填入数据后，根据[SearchView](http://developer.android.com/reference/android/widget/SearchView.html)提供的请求搜索数据。将下面的方法添加到`DatabaseTable`类中，用来创建搜索请求的SQL语句: ~~~ public Cursor getWordMatches(String query, String[] columns) { String selection = COL_WORD + " MATCH ?"; String[] selectionArgs = new String[] {query+"*"}; return query(selection, selectionArgs, columns); } private Cursor query(String selection, String[] selectionArgs, String[] columns) { SQLiteQueryBuilder builder = new SQLiteQueryBuilder(); builder.setTables(FTS_VIRTUAL_TABLE); Cursor cursor = builder.query(mDatabaseOpenHelper.getReadableDatabase(), columns, selection, selectionArgs, null, null, null); if (cursor == null) { return null; } else if (!cursor.moveToFirst()) { cursor.close(); return null; } return cursor; } ~~~ 调用`getWordMatches()`来搜索请求。任何符合的结果返回到[Cursor](http://developer.android.com/reference/android/database/Cursor.html)中，可以直接遍历或是建立一个[ListView](http://developer.android.com/reference/android/widget/ListView.html)。这个例子是在检索[activity](# "An activity represents a single screen with a user interface.")的`handleIntent()`方法中调用`getWordMatches()`。请记住，因为之前创建的intent filter，检索[activity](# "An activity represents a single screen with a user interface.")会在[ACTION_SEARCH](http://developer.android.com/reference/android/content/Intent.html#ACTION_SEARCH) intent中额外接收请求作为变量存储: ~~~ DatabaseTable db = new DatabaseTable(this); ... private void handleIntent(Intent intent) { if (Intent.ACTION_SEARCH.equals(intent.getAction())) { String query = intent.getStringExtra(SearchManager.QUERY); Cursor c = db.getWordMatches(query, null); //执行Cursor并显示结果 } } ~~~