Why does the GalleryView not refresh with new items?

Question

I am going crazy trying to figure this out. I have tried everything I knew and nothing seem to be working. Any help in the right direction is much appreciated.

GalleryView does not refresh when in the same activity I press a button to start a ProgressDialog (in onPreExecute() method of AsyncTask) to update the String array that holds the items to be displayed in the GalleryView. In onPostExecute() of AsyncTask, I tried to call notifyDataSetChanged() on my adapter followed by setAdapter() on the GalleryView. onPostExecute(), I believe, works on the UI thread. Also, I tried calling notifyDataSetChanged() and setAdapter() in runOnUiThread() but that doesn't seem to work either. GalleryView does not refresh automatically with new items. It does, only when I scroll the view out of the screen and then back in again. The view updates with the new item only then.

Below is the code in parts:

On button click event, calling execute on UpdateGalleryview that extends AsyncTask

refresh.setOnClickListener(new Button.OnClickListener() {
        public void onClick(View v) {

            UpdateGalleryview updateGalleryview=new UpdateGalleryview();
            updateGalleryview.execute(GalleryView.this);
     }
});

Then in onPreExecute() method of UpdateGalleryview class, I am creating a ProgressDialog and updating the array that is sent to the Adapter of GalleryView.

private class UpdateGalleryview extends AsyncTask<Context, Integer, String>
{   

@Override
 protected void onPreExecute() 
 {
     final ProgressDialog dialog = ProgressDialog.show(GalleryView.this, "Refresh", "Loading... please wait", true);

     new Thread(new Runnable(){
        public void run(){

         //Updating the Uri[] that is sent to the Adapter for GalleryView
             File[] imagelist;
             File images = new File("/sdcard/thumbs/");
            imagelist = images.listFiles();

            mFiles = new String[imagelist.length];

            for(int i= 0 ; i< imagelist.length; i++){

                   mFiles[i] = imagelist[i].getAbsolutePath();

            }

            mUrls = new Uri[mFiles.length];

        for(int i=0; i < mFiles.length; i++){

            mUrls[i] = Uri.parse(mFiles[i]); 

        }

         dialog.dismiss();
    }

    }).start();

     Log.i( TAG, "onPreExecute()" );
     super.onPreExecute();

 }

Then, in onPostExecute() of AsyncTask, I am calling another thread that runs on UI

@Override
 protected void onPostExecute( String result ) 
 {
        runOnUiThread(updateAdapter); 
//          gaAdapter.notifyDataSetChanged();

//          ga.setAdapter(gaAdapter);
//          ga.invalidate();
//          ga.setSelection(midposition);

         super.onPostExecute(result);

 }

As you can see above, I even tried to update the Adapter (gaAdapter) with new items and the GalleryView (ga) within onPostExecute() itself. But that didn't work. So I created the new thread to do it, as below.

private Runnable updateAdapter = new Runnable() { 
        @Override 
        public void run() { 
                // TODO Auto-generated method stub 
            gaAdapter.notifyDataSetChanged();

            ga.setAdapter(gaAdapter);
//                    ga.invalidate();
            ga.setSelection(midposition);
        } 
}; 

This is my Adapter code

public class ImageAdapter extends BaseAdapter {

    private Context ctx;
    int imageBackground;

    public ImageAdapter(Context c) {
        ctx = c;
        TypedArray ta = obtainStyledAttributes(R.styleable.Gallery1);
        imageBackground = ta.getResourceId(R.styleable.Gallery1_android_galleryItemBackground, 1);
        ta.recycle();
    }

    @Override
    public int getCount() {

        return imagelist.length;
    }

    @Override
    public Object getItem(int arg0) {

        return arg0;
    }

    @Override
    public long getItemId(int arg0) {

        return arg0;
    }

    @Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {
        ImageView iv = new ImageView(ctx);

        iv.setImageURI(mUrls[arg0]);

        iv.setScaleType(ImageView.ScaleType.CENTER_INSIDE);
        iv.setLayoutParams(new Gallery.LayoutParams(180,144));
        iv.setBackgroundResource(imageBackground);

        return iv;
    }

}

This is where I am at. GalleryView does not refresh automatically by doing the above.

Answer 1

You should be updating the array you use when you create the adapter the first time. You'll probably need to keep a reference to it in your class. Update that array, and then call notifyDataSetChanged.