> 編寫:[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) 有很多方法可以儲存你的數據，比如儲存在線上的數據庫，本地的SQLite數據庫，甚至是文本文件。你自己來選擇最適合你應用的存儲方式。本節課程會向你展示如何創建一個健壯的可以提供全文搜索的SQLite虛擬表。并從一個每行有一組單詞-解釋對的文件中將數據填入。 ### 創建虛擬表 虛擬表與SQLite表的運行方式類似，但虛擬表是通過回調來向內存中的對象進行讀取和寫入，而不是通過數據庫文件。要創建一個虛擬表，首先為該表創建一個類: ~~~ public class DatabaseTable { private final DatabaseOpenHelper mDatabaseOpenHelper; public DatabaseTable(Context context) { mDatabaseOpenHelper = new DatabaseOpenHelper(context); } } ~~~ 在`DatabaseTable`類中創建一個繼承[SQLiteOpenHelper](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html)的內部類。你必須重寫類[SQLiteOpenHelper](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html)中定義的abstract方法，才能在必要的時候創建和更新你的數據庫表。例如，下面一段代碼聲明了一個數據庫表，用來儲存字典app所需的單詞。 ~~~ public class DatabaseTable { private static final String TAG = "DictionaryDatabase"; //字典的表中將要包含的列項 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); } } } ~~~ ### 填入虛擬表 現在，表需要數據來儲存。下面的代碼會向你展示如何讀取一個內容為單詞和解釋的文本文件(位于`res/raw/definitions.txt`)，如何解析文件與如何將文件中的數據按行插入虛擬表中。為防止UI鎖死這些操作會在另一條線程中執行。將下面的一段代碼添加到你的`DatabaseOpenHelper`內部類中。 > **Tip**:你也可以設置一個回調來通知你的UI [activity](# "An activity represents a single screen with a user interface.")線程的完成結果。 ~~~ 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); } ~~~ 任何恰當的地方，都可以調用`loadDictionary()`方法向表中填入數據。一個比較好的地方是`DatabaseOpenHelper`類的[onCreate()](http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html#onCreate(android.database.sqlite.SQLiteDatabase))方法中，緊隨創建表之后: ~~~ @Override public void onCreate(SQLiteDatabase db) { mDatabase = db; mDatabase.execSQL(FTS_TABLE_CREATE); loadDictionary(); } ~~~ ### 搜索請求 當你的虛擬表創建好并填入數據后，根據[SearchView](http://developer.android.com/reference/android/widget/SearchView.html)提供的請求搜索數據。將下面的方法添加到`DatabaseTable`類中，用來創建搜索請求的SQL語句: ~~~ 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; } ~~~ 調用`getWordMatches()`來搜索請求。任何符合的結果返回到[Cursor](http://developer.android.com/reference/android/database/Cursor.html)中，可以直接遍歷或是建立一個[ListView](http://developer.android.com/reference/android/widget/ListView.html)。這個例子是在檢索[activity](# "An activity represents a single screen with a user interface.")的`handleIntent()`方法中調用`getWordMatches()`。請記住，因為之前創建的intent filter，檢索[activity](# "An activity represents a single screen with a user interface.")會在[ACTION_SEARCH](http://developer.android.com/reference/android/content/Intent.html#ACTION_SEARCH) intent中額外接收請求作為變量存儲: ~~~ 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); //執行Cursor并顯示結果 } } ~~~