Question

I’ve got this inner class as part of an application which doesn’t accept changes in orientation (it makes more sense in landscape orientation).

  private class initialDBQuery extends AsyncTask<SQLiteDatabase, Void, Cursor> {

    @Override
    protected Cursor doInBackground(SQLiteDatabase... params) {
        final SQLiteDatabase mDatabase = params[0];
        mCursor = mDatabase.rawQuery("SELECT * FROM database", null);
        return mCursor;
    }

    @Override
    protected void onPostExecute(Cursor c){

        ParentActivity.this.mCursor = mCursor; 
        ParentActivity.this.updateQuery();
        mDatabase.close(); //Close database connection ASAP
    }

    // can use UI thread here
    protected void onPreExecute() {
        ParentActivity.this.mAnimalPager = null;
        Toast.makeText(ParentActivity.this.getBaseContext(), "Loading Database...", Toast.LENGTH_SHORT).show();
    }
} 

My main UI has a number of buttons which lead to different activities, the function of which is to provide search criteria via intents to the main activity (ParentActivity) which will then perform a search. the rest of the main activity is a viewpager which dependsonthe cursor returned from the AsyncTask (the update of this is working fine).

My problem is that: with this code i, I press one of the onscreen buttons (launch another activity) while the asynctask is running then I get the error “Unable to pause activity”.

what are the further steps I need to take to deal with the running of the AsyncTask when the app pauses?

thanks, m

Answer 1

The problem I was experiencing here was actually to do with the viewpager I have on the main activity.

As the AsyncTask was creating a cursor for the PagerAdapter i wasn’t setting the adapter until it had finished. There is a known problem with ViewPagers and activity onPause when an adapter has not been set (see here).

To overcome this I modified my adapter to return 0 when there is no cursor available to the adapter:

public int getCount() {
    // return the size of the cursor if it has been instantiated; 
    return (mCursor !=null) ? mCursor.getCount() : 0 ; 
}

and added a setCurrentCursor method to the adapter. This way I was able to set the adapter up and bind it to the viewpager in onCreate and then add the cursor to the adapter when it became available from the ASyncTask;

    public void setCurrentCursor(Cursor cu){
    this.mCursor = cu; 
    this.notifyDataSetChanged();
}

Now all I have to do is call adapter.setCurrentCursor in the onPostExecute method of the ASyncTask passing in the created cursor.

Hope this helps.

Thanks,
m