Android SQLite錯誤打開數據庫

Question

我正在使用SQLiteOpenHelper，而且我的類工作得很好，但是在從遊標獲取getCount（）後沒有關閉數據庫的其中一個方法中發生了錯誤。現在，每次我啓動應用程序，我得到的錯誤：

java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: 

我試圖關閉連接，但我無法與該類執行任何方法，因爲我總是得到這個錯誤。

我實際上重新創建了一個全新的Android應用程序，並逐個複製了我的源文件，並且仍然收到相同的錯誤。

在我MainActivity.java：

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    BillDatabaseHelper db = new BillDatabaseHelper(this); 
    db.recreateDatabases(); // this is the line that causes the error 

    viewPagerFragment = new ViewPagerFragment(); 
    transaction = manager.beginTransaction(); 
    transaction.add(R.id.placeholderMain, viewPagerFragment); 
    transaction.commit(); 
} 

在我DatabaseHelper.java：

public void recreateDatabases() { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    onCreate(db); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_TRANSACTIONS); 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_BILL_INFO); 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_REMINDERS); 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_BILL_DATE_INFO); 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_PAYDATES); 

    String strCreateTransactionsTableSQL = 
      "CREATE TABLE " + TABLE_TRANSACTIONS + "(" 
      + KEY_TRAN_ID + " INTEGER PRIMARY KEY," 
      + KEY_TRAN_DESC + " TEXT," 
      + KEY_TRAN_AMOUNT + " REAL," 
      + KEY_TRAN_PURCHASE_DATE + " TEXT);"; 

    String strCreateBillInfoTableSQL = 
      "CREATE TABLE " + TABLE_BILL_INFO + "(" 
      + KEY_BILL_ID + " INTEGER PRIMARY KEY," 
      + KEY_BILL_NAME + " TEXT," 
      + KEY_BILL_BALANCE + " FLOAT," 
      + KEY_BILL_DUE_DATE + " TEXT," 
      + KEY_BILL_MINIMUM + " FLOAT," 
      + KEY_BILL_CURRENT + " FLOAT);"; 

    String strCreateRemindersTableSQL = 
      "CREATE TABLE " + TABLE_REMINDERS + "(" 
      + KEY_REM_ID + " INTEGER PRIMARY KEY," 
      + KEY_REM_NAME + " TEXT," 
      + KEY_REM_DESC + " TEXT," 
      + KEY_REM_LOCATION + " TEXT," 
      + KEY_REM_START + " TEXT);"; 

    String strCreateBillDateTableSQL = 
      "CREATE TABLE " + TABLE_BILL_DATE_INFO + "(" 
      + KEY_BILLDATE_PK + " INTEGER PRIMARY KEY," 
      + KEY_BILLDATE_TOBILL_ID + " INTEGER," 
      + KEY_BILLDATE_BILLID + " INTEGER," 
      + KEY_BILLDATE_PAYDATE + " TEXT," 
      + KEY_BILLDATE_BILLDATE + " TEXT," 
      + KEY_BILLDATE_OWEDTODAY + " CHARACTER(1)," 
      + KEY_BILLDATE_BALANCE + " FLOAT," 
      + KEY_BILLDATE_CURRENT + " FLOAT," 
      + "FOREIGN KEY(" + KEY_BILLDATE_PK + ") REFERENCES " + TABLE_BILL_INFO + "(" + KEY_BILL_ID + "));"; 

    String strCreatePaydatesSQL = 
      "CREATE TABLE " + TABLE_PAYDATES + "(" 
      + KEY_PAYDATE_ID + " INTEGER PRIMARY KEY," 
      + KEY_PAYDATE_DATE + " TEXT);"; 

    db.execSQL(strCreateTransactionsTableSQL); 
    db.execSQL(strCreateBillInfoTableSQL); 
    db.execSQL(strCreateRemindersTableSQL); 
    db.execSQL(strCreateBillDateTableSQL); 
    db.execSQL(strCreatePaydatesSQL); 
} 

應該在哪裏我可以關閉此連接？任何幫助將不勝感激。

Answer 1

您不必關閉數據庫連接，請參閱：

Best place to close database connection

您可以留下一個數據庫，這樣打開：

public class YourDatabase extends SQLiteOpenHelper { 

    public static final int DATABASE_VERSION = 1; 
    public static final String DATABASE_NAME = "yourdatabase.db"; 
    private SQLiteDatabase database; 

    public YourDatabase(Context context) { 
     super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    } 

    // call this function once 
    public void open() throws SQLException { 
     database = this.getWritableDatabase(); 
    } 

    private void create(SQLiteDatabase database) { 
     database.execSQL("CREATE TABLE contacts (TEXT `name`, TEXT `number`)"); 
    } 

    @Override 
    public void onCreate(SQLiteDatabase database) { 
     create(database); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     // TODO Auto-generated method stub 
    } 
} 

就叫open()一次，然後你可以使用database屬性來寫入或讀取數據庫，如下所示database.rawQuery(selectQuery, null);