Question

I am looking for best approach to handling database connection. I have designed my application base on following method and works fine. However, sometimes application crashes especially on old model devices. Please look at my following method.

I have a DatabaseHelper class which all of tables will be created here. This class is like this:

public class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);

        Log.i(TAG, "Object created.");
    }

@Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CRT_TBL_1);
        db.execSQL(CRT_TBL_2);
        db.execSQL(CRT_TBL_3);
        db.execSQL(CRT_TBL_4);
        db.execSQL(CRT_TBL_5);
        db.execSQL(CRT_TBL_6);
        db.execSQL(CRT_TBL_7);
        db.execSQL(CRT_TBL_8);
    }

@Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(DatabaseHelper.class.getName(), "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data.");

        onCreate(db);
    }
}

As you have seen, I have 8 tables which provides data for 8 different activities. Implementation of handler class for one activity is like following code.

public class DatabaseHandler_1 {

    private final String TAG = "DatabaseHandler_1 ";

    private DatabaseHelper dbHelper;
    private SQLiteDatabase database;

    public DatabaseHandler_1 (Context context) {
        dbHelper = new DatabaseHelper(context);

        Log.i(TAG, "Object created.");
    }

    public void open() throws SQLException {
        database = dbHelper.getWritableDatabase();
    }

    public void close() {
        dbHelper.close();
    }

// ... Other methods insert, update, query, ...
}

Finally, based on required information one or some of them will be used in each activity.

public class Activity_1 {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "Try to create activity...");

        // Creating Database/Table
        dbHandler_1 = new DatabaseHandler_1 (this);
        dbHandler_1 .open();
        dbHandler_2 = new DatabaseHandler_2 (this);
        dbHandler_2 .open();
        dbHandler_3 = new DatabaseHandler_3 (this);
        dbHandler_3 .open();
    }

     @Override
     protected void onDestroy() {
        super.onDestroy();

        // Closing database
        dbRecipesHandler.close();
        dbFavoritsHandler.close();
        dbShoppingHandler.close();
     }

        // Other methods for displaying data...
}

When crashes happens logcat shows the connection is close while my application tries to query in database. I think scenario is like this:
User opens 1’st activity then he goes to second activity and then he goes to third activity. Now, if user clicks on back button third activity will be closed and onDestroy() method of this activity closes database connection. Because, second activity is still in memory, activity assumes that the connection is still open and when it wants to query into database, crash happens.

Logcat shows a message like this: Database connection is close. You wanted to query…

One solution is instead of letting Android OS handles database connection, we manually open connection and use it the manually close it.
Second solution is in Handler class manually open and close connection for each method.

What is you suggestion? did you have any experience about it?
Any suggestion would be appreciated.

Answer 1

Finally I solved the problem. I thought that I should open database one time in activity. I tried to open database again in onResume() method of each activity and closing it in onPause() of each activity instead of closing in onDestroy() method.

So far problem solved. Hope to don’t see it again. If i face it again then will update/remove answer.