Android SQLite错误打开数据库

Question

我正在使用SQLiteOpenHelper，而且我的类工作得很好，但是在从游标获取getCount（）后没有关闭数据库的其中一个方法中发生了错误。现在，每次我启动应用程序，我得到的错误：

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

我试图关闭连接，但我无法与该类执行任何方法，因为我总是得到这个错误。

我实际上重新创建了一个全新的Android应用程序，并逐个复制了我的源文件，并且仍然收到相同的错误。

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); 
} 

应该在哪里我可以关闭此连接？任何帮助将不胜感激。

Answer 1

您不必关闭数据库连接，请参阅：

Best place to close database connection

您可以留下一个数据库，这样打开：

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，然后你可以使用database属性来写入或读取数据库，如下所示database.rawQuery(selectQuery, null);