Android database connection and cursor Oh, my

When using Android, I have read a lot of blogs and tutorials on how to create and use database connections. Although I have many working examples, different implementations will lead to different problems

For example, I use the data source class, data source and database assistant class dbmanage

data source

public class DataSource {
    // Database fields
    private sqliteDatabase database;
    private DBManagement dbHelper;

    public SMSDataSource(Context context) {
        dbHelper = new DBManagement(context);
    }

    public void open() throws sqlException {
        if(database == null){
             database = dbHelper.getWritableDatabase();
        }
    }

public Cursor exampleCursor(long constraint){
    Cursor cur = database.query(DBManagement.TABLE_NAME,
            new String[] {DBManagement.Column}, "constraint="+constraint, null, null, null, null);
    return cur;
}
    //.. other methods down here which do rawQuery, QueryBuilder, etc.. 

DBManagement

public class DBManagement extends sqliteOpenHelper{

    // .. table deFinitions and columns etc ..//

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

In the oncreate method in the activity, I will call datasource. Open() and the SQL connection has been opened. Then I will do the following:

DataSource datasource = new DataSource();

Cursor cursor = datasource.exampleCursor(1);
startManagingCursor(cursor);

If I navigate to a new activity, I receive the following error:

 06-27 21:59:14.812: E/Database(13396): close() was never explicitly called on database '/data/data/com.example.package/databases/db.db' 

If I add datasource. Close(); At the end of oncreate, no simple cursor adapter works, or if I perform an operation on the conextual menu, I get an error that DB is not opened

What is the best way to deal with the above problems?

So I did the following, and I still encountered database problems:

@Override
public void onBackPressed() {
    // do something on back.
    //Log.i(getClass().toString(), "onBackPressed");

    datasource.close();

    finish();
    return;
}

@Override
protected void onResume(){
    super.onResume();
    onCreate(null);
}


@Override
protected void onRestart(){
    datasource = new DataSource(this);
    datasource.open();

    filters = datasource.getFilterCursor();
    startManagingCursor(filters);

    super.onRestart();
}

@Override
protected void onPause(){
    //Log.i(getClass().toString(), "onPause");
    ((CursorAdapter) adapter).getCursor().close();
    datasource.close();
    super.onPause();
}   
@Override
protected void onStop(){
    //Log.i(getClass().toString(), "onStop");
    datasource.close();
    super.onStop();
}

My datasource.java class has the following contents:

public Datasource(Context context){
     dbHelper = new DBManagement(context);
}

public void open() throws sqlException {
    if( database == null ){
           database = dbHelper.getWritableDatabase();
    }
}

public void close(){
    if(dbHelper != null){
         dbHelper.close();
    }
}

resolvent:

This is actually very simple:

>After completion, explicitly close all cursors (last used), etc. > do not use startmanagingcursor() > make your database wrapper / Assistant / Manager / no matter what kind of detail > do not explicitly call close() on the database assistant. When your process terminates, I will close automatically

In addition: frequent opening and closing is definitely a bad idea because it brings a lot of overhead

Using a loader is also an option. You absolutely don't need to use a content provider to use a loader, but it's not that simple. Using a content provider involves IPC. If you don't intend to export data to other applications, there will usually be excessive killing