Error (android.os.NetworkOnMainThreadException) while downloading images from the server showing in ListView using AsyncTask

Issue

I am facing some problem while downloading images from the server and showing in the ListView using AsyncTask in Android.

It showing me error that downloading the images are in the Main (UI) Thread But I am using the AsyncTask for that purpose.

Here is my MainActivity.java code.

public class MainActivity extends AppCompatActivity {

    private String[] imageURLArray = new String[]{
            "http://farm8.staticflickr.com/7315/9046944633_881f24c4fa_s.jpg",
            "http://farm4.staticflickr.com/3777/9049174610_bf51be8a07_s.jpg",
            "http://farm8.staticflickr.com/7324/9046946887_d96a28376c_s.jpg",
            "http://farm3.staticflickr.com/2828/9046946983_923887b17d_s.jpg",
            "http://farm4.staticflickr.com/3810/9046947167_3a51fffa0b_s.jpg",
            "http://farm4.staticflickr.com/3773/9049175264_b0ea30fa75_s.jpg",
            "http://farm4.staticflickr.com/3781/9046945893_f27db35c7e_s.jpg",
            "http://farm6.staticflickr.com/5344/9049177018_4621cb63db_s.jpg",
            "http://farm8.staticflickr.com/7307/9046947621_67e0394f7b_s.jpg",
            "http://farm6.staticflickr.com/5457/9046948185_3be564ac10_s.jpg",
            "http://farm4.staticflickr.com/3752/9046946459_a41fbfe614_s.jpg",
            "http://farm8.staticflickr.com/7403/9046946715_85f13b91e5_s.jpg",
            "http://farm8.staticflickr.com/7315/9046944633_881f24c4fa_s.jpg",
            "http://farm4.staticflickr.com/3777/9049174610_bf51be8a07_s.jpg",
            "http://farm8.staticflickr.com/7324/9046946887_d96a28376c_s.jpg",
            "http://farm3.staticflickr.com/2828/9046946983_923887b17d_s.jpg",
            "http://farm4.staticflickr.com/3810/9046947167_3a51fffa0b_s.jpg",
            "http://farm4.staticflickr.com/3773/9049175264_b0ea30fa75_s.jpg",
            "http://farm4.staticflickr.com/3781/9046945893_f27db35c7e_s.jpg",
            "http://farm6.staticflickr.com/5344/9049177018_4621cb63db_s.jpg",
            "http://farm8.staticflickr.com/7307/9046947621_67e0394f7b_s.jpg",
            "http://farm6.staticflickr.com/5457/9046948185_3be564ac10_s.jpg",
            "http://farm4.staticflickr.com/3752/9046946459_a41fbfe614_s.jpg",
            "http://farm8.staticflickr.com/7403/9046946715_85f13b91e5_s.jpg"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView listView = (ListView)this.findViewById(R.id.listView);
        ImageAdapter imageAdapter = new ImageAdapter(this, R.layout.imageitem, imageURLArray);
        listView.setAdapter(imageAdapter);
    }
}

Here is my ImageAdapter.java code.

public class ImageAdapter extends ArrayAdapter<String> {
    private String[] imageURLArray;
    private LayoutInflater inflater;

    public ImageAdapter(Context context, int textViewResourceId,
                        String[] imageArray) {
        super(context, textViewResourceId, imageArray);
        // TODO Auto-generated constructor stub

        inflater = ((Activity) context).getLayoutInflater();
        imageURLArray = imageArray;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        ViewHolder viewHolder = null;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.imageitem, null);
            viewHolder = new ViewHolder();
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.testImage);
            convertView.setTag(viewHolder);
        }

        viewHolder = (ViewHolder) convertView.getTag();
        Bitmap imageBitmap = null;
        try {
            URL imageURL = new URL(imageURLArray[position]);
            imageBitmap = BitmapFactory.decodeStream(imageURL.openStream());
            viewHolder.imageView.setImageBitmap(imageBitmap);
        } catch (IOException e) {
            // TODO: handle exception
            Log.e("error", "Downloading Image Failed");
            viewHolder.imageView.setImageResource(R.mipmap.ic_launcher);
        }

        return convertView;
    }

    private static class ViewHolder {
        Bitmap bitmap;
        String imageURL;
        ImageView imageView;
    }

    private class DownloadAsyncTask extends AsyncTask<ViewHolder, Void, ViewHolder> {
        @Override
        protected ViewHolder doInBackground(ViewHolder... params) {
            // TODO Auto-generated method stub
            //load image directly
            ViewHolder viewHolder = params[0];
            try {
                URL imageURL = new URL(viewHolder.imageURL);
                viewHolder.bitmap = BitmapFactory.decodeStream(imageURL.openStream());
            } catch (IOException e) {
                // TODO: handle exception
                Log.e("error", "Downloading Image Failed");
                viewHolder.bitmap = null;
            }

            return viewHolder;
        }

        @Override
        protected void onPostExecute(ViewHolder result) {
            if (result.bitmap == null) {
                result.imageView.setImageResource(R.mipmap.ic_launcher);
            } else {
                result.imageView.setImageBitmap(result.bitmap);
            }
        }
    }
}

Here is the link that have the full project.

http://www.mediafire.com/download/70pxv6ib584x9j7/DownloadImagesInListView.rar

Here is the error stack that is showing.

09-29 18:33:37.859    5550-5550/com.example.android.downloadimagesinlistview E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.android.downloadimagesinlistview, PID: 5550
    android.os.NetworkOnMainThreadException
            at 

    android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1161)
                at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
                at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
                at java.net.InetAddress.getAllByName(InetAddress.java:215)
                at com.android.okhttp.HostResolver$1.getAllByName(HostResolver.java:29)
                at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:232)
                at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:124)
                at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:272)
                at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:211)
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:382)
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:332)
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:199)
                at java.net.URL.openStream(URL.java:470)
                at com.example.android.downloadimagesinlistview.ImageAdapter.getView(ImageAdapter.java:48)
                at android.widget.AbsListView.obtainView(AbsListView.java:2347)
                at android.widget.ListView.makeAndAddView(ListView.java:1864)
                at android.widget.ListView.fillDown(ListView.java:698)
                at android.widget.ListView.fillFromTop(ListView.java:759)
                at android.widget.ListView.layoutChildren(ListView.java:1673)
                at android.widget.AbsListView.onLayout(AbsListView.java:2151)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
                at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
                at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
                at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.support.v7.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:437)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
                at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
                at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
                at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
                at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
                at android.view.View.layout(View.java:15689)
                at android.view.ViewGroup.layout(ViewGroup.java:5040)
                at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2116)
                at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1873)
                at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1084)
                at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5990)
                at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
                at android.view.Choreographer.doCallbacks(Choreographer.java:580)
                at android.view.Choreographer.doFrame(Choreographer.java:550)
                at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
                at android.os.Handler.handleCallback(Handler.java:739)
                at android.os.Handler.dispatchMessage(Handler.java:95)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5343)
                at java.lang.reflect.Method.invoke(

Solution

This exception occurs when you perform network related operations on the main thread. For downloading the images either you have to perform the operation in AsyncTask or Use picasso library.

Using Picasso use this

Picasso.with(MainActivity.this).load(imageURLArray[position]).error(R.mipmap.ic_launcher).into(viewHolder.imageView);

at the place of

Bitmap imageBitmap = null;
try {
  URL imageURL = new URL(imageURLArray[position]);
  imageBitmap = BitmapFactory.decodeStream(imageURL.openStream());
  viewHolder.imageView.setImageBitmap(imageBitmap);
} catch (IOException e) {
  // TODO: handle exception
  Log.e("error", "Downloading Image Failed");
  viewHolder.imageView.setImageResource(R.mipmap.ic_launcher);
}

Answered By - Deepak Goyal