Fix Resource Leak

[maxwai]

During executions a lot of Log Messages from the System stating A resource failed to call AbstractCursor.close. are generated. This doesn't lead to crashed but should be fixed nevertheless.

[MortusMg]

The message "A resource failed to call AbstractCursor.close" is a warning that typically appears when a cursor, which is used to interact with a database in an Android app, is not closed properly after being used. While this doesn’t cause crashes immediately, it can lead to memory leaks and performance issues over time.

Here’s how to fix it in a way that’s simple and easy to implement:

1. Always Close the Cursor

Whenever you’re using a cursor to query a database, make sure to close it once you're done with it. The easiest way to do this is by using a finally block, which ensures the cursor gets closed even if something goes wrong.

Example:

Cursor cursor = null; try { cursor = db.query("table_name", null, null, null, null, null, null); // Do something with the cursor here if (cursor != null && cursor.moveToFirst()) { // Process data from the cursor } } catch (Exception e) { e.printStackTrace(); } finally { if (cursor != null) { cursor.close(); // Always close it here } }

2. Use Try-With-Resources (Java 7 and Above)

If your app is using Java 7 or newer, you can simplify this by using try-with-resources. This feature automatically closes resources like cursors, so you don’t have to manually close them. This is a cleaner and safer approach.

Example with try-with-resources:

try (Cursor cursor = db.query("table_name", null, null, null, null, null, null)) { // Do something with the cursor here if (cursor != null && cursor.moveToFirst()) { // Process data from the cursor } } catch (Exception e) { e.printStackTrace(); } // No need for cursor.close() - it’s handled automatically.

3. Review All Database Interactions

Check the rest of your app for any other places where you're querying the database and working with cursors. Be sure every cursor that’s opened gets closed properly. This includes calls to query(), rawQuery(), or any database interactions that return a cursor.

For example:

SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.query("table_name", null, null, null, null, null, null); try { // Use the cursor for your work here } finally { cursor.close(); // Don’t forget to close it }

4. Watch Out for Other Libraries

If you're using libraries (e.g., third-party database libraries) to handle your database, ensure they’re following the same practice of closing cursors after use. Sometimes, libraries can manage cursors for you, but you should double-check to avoid any issues.

5. Optimize Your Queries

To prevent holding unnecessary data in memory, make sure your database queries are as efficient as possible. Only request the data you actually need, as it reduces the chance of problems related to cursor management.

Bottom Line

The key to fixing the "AbstractCursor.close" warning is simple: always close your cursors when you’re done with them. Using a finally block or try-with-resources ensures that you don’t forget to clean up after yourself. This will keep your app’s memory use under control and prevent those warning messages from popping up.