Answer by Krishna for How do I fix 'android.os.NetworkOnMainThreadException'?

You are not allowed to implement network operations on the UI thread on Android. You will have to use AsyncTask class to perform network related operations like sending API request, downloading image from a URL, etc. and using callback methods of AsyncTask, you can get you result in onPostExecute menthod and you will be in the UI thread and you can populate UI with data from web service or something like that.

Example: Suppose you want to download image from an URL: https://www.samplewebsite.com/sampleimage.jpg

Solution using AsyncTask: are respectively.

    public class MyDownloader extends AsyncTask<String,Void,Bitmap>
    {
        @Override
        protected void onPreExecute() {
            // Show progress dialog
            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            //Populate Ui
            super.onPostExecute(bitmap);
        }

        @Override
        protected Bitmap doInBackground(String... params) {
            // Open URL connection read bitmaps and return form here
            return result;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            // Show progress update
            super.onProgressUpdate(values);
        }


    }
}

Note: Do not forget to add the Internet permission in the Android manifest file. It will work like a charm. :)