Question

My expected result is in the first launch there will display a progress dialog to wait for the background thread loading the content. The dialog dismisses after worker thread is done the job. I did search and got this solution How to display progress dialog before starting an activity in Android?

This is my complete code:

    private ManagerApplication app;
    private ImageAdapter adapter;
    private GridView gridview;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        setupView();      
    }

    private void setupView() {
        gridview = (GridView) findViewById(R.id.gridview);
        app = (ManagerApplication) getApplication();
        ProgressDialog progress = new ProgressDialog(this);
        progress.setMessage("Loading...");
        new LoadImageTask(progress, this).execute();       
    }

    private class LoadImageTask extends AsyncTask<Void, Void, Void> {
        private ProgressDialog progress;
        private Context context;

        public LoadImageTask(ProgressDialog progress, Context context) {
            this.progress = progress;
            this.context = context;
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progress.show();
        }

        @Override
        protected Void doInBackground(Void... params) {
            adapter = new ImageAdapter(app.getShoes(), context);
            gridview.setAdapter(adapter); 
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            progress.dismiss();
        }

    }

However, my application crashes with the reason that “Only the original thread that created a view hierarchy can touch its views”. I suppose there are something blocked the main UI thread, but its still very unclear. So could anyone point me to the problem ? Thanks

Answer 1

doinBackground is non UI Thread ,So never update any UI(View) in this
method…

and use OnPostExecute or OnProgressUpdate for update UI

 @Override
        protected Void doInBackground(Void... params) {
           //here just background task ,
     //its non UI Thread so dont set ant view here set it in OnPostExecute,...
            return null;
        }

call asynctask from setupview

private void setupView() {
        gridview = (GridView) findViewById(R.id.gridview);
        app = (ManagerApplication) getApplication();

        new LoadImageTask(progress, this).execute();       
  }

and create ProgressDilog in OnPreExecute method

ProgressDialog progress;

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

     progress = new ProgressDialog(this);
     progress.setMessage("Loading...");
     progress.show();
    }

and in onPostExecute dismiss it