java - Android - ViewRootImpl$CalledFromWrongThreadException

Question

I was using this, to DISPLAY IMAGES FROM THE INTERNET but it throws an error as below:
04-12 13:45:05.337: E/AndroidRuntime(27897): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

public class Order extends Activity {
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            new DownloadFilesTask().execute();       
        }    
        private class DownloadFilesTask extends AsyncTask<Void, Void, Void> {
            protected void onPostExecute(Void result) {
            }
             @Override
             protected Void doInBackground(Void... params) {
                 setContentView(R.layout.order);
                    ImageView imageView = (ImageView)findViewById(R.id.imgView);  
                    imageView.setImageDrawable(createDrawableFromURL("http://savagelook.com/misc/sl_drop2.png"));
                    return null;
             }          
        }     
        private Drawable createDrawableFromURL(String urlString) {
            Drawable image = null;
        try {
            URL url = new URL(urlString);
            InputStream is = (InputStream)url.getContent();
            image = Drawable.createFromStream(is, "src");
        } catch (MalformedURLException e) {
            image = null;
        } catch (IOException e) {
            image = null;
        } 
        return image;
        }

}

Answer 1

I got the same problem trying to change UI view from c++ using JNI. The solution was use

runOnUiThread(new Runnable() {
    public void run(){   
    }
});

runOnUiThread is an Activity method so I have to make my activity instance public static to be able to call on my public static method who later call from JNI.

Hope this help others :)

PS: from here I learn how to use JNI http://www.cocos2d-x.org/projects/cocos2d-x/wiki/How_to_use_jni for my android game previously made with cocos2dx