How do I implement this image view in an async task?

Question

I have an url passed to an activity and I am trying to show the image from the url full screen, however it throws a main network thread exception.

From what I can find I believe I have to put the method in an async task however I cannot seem to make sense of it at all. So how would I put this method in an async task?

FullScreenImageView.java

public class FullscreenImageView extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    String url = getIntent().getStringExtra("SelectedImageURL");



    try {
        ImageView i = (ImageView)findViewById(R.id.imgView);
        Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url).getContent());
        i.setImageBitmap(bitmap);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}
}

put `BitmapFactory.decodeStream` into doInBackground return Bitmap and in onPostExecute set this bitmap to image — Selvin, Sep 17 '14 at 13:22
http://www.learn2crack.com/2014/06/android-load-image-from-internet.html — Naveen Tamrakar, Sep 17 '14 at 13:22
possible duplicate of [android.os.NetworkOnMainThreadException](http://stackoverflow.com/questions/6343166/android-os-networkonmainthreadexception) — panini, Sep 19 '14 at 04:39

score 2 · Accepted Answer · edited Sep 17 '14 at 13:42

2

It should be something like this. In the doInBackground you get the image, and in the onPostExecute you set it

private class DownloadFilesTask extends AsyncTask<String, Void, Bitmap>  {
     @Override
     protected Bitmap doInBackground(String... urls) {
          Bitmap bitmap = null; 
          try {
              bitmap = BitmapFactory.decodeStream((InputStream)new URL(urls[0]).getContent());
          } catch (MalformedURLException e) {
               e.printStackTrace();
          } catch (IOException e) {
             e.printStackTrace();
          }
          return bitmap;
     }
     @Override
     protected void onPostExecute(Bitmap bitmap) {
        ImageView i = (ImageView)findViewById(R.id.imgView);
        i.setImageBitmap(bitmap);
     }
 }

Then, you call it inside your onCreate method

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String url = getIntent().getStringExtra("SelectedImageURL");
    new DownloadFilesTask ().execute(url); 
}

edited Sep 17 '14 at 13:42

Selvin

6,598
3
37
43

answered Sep 17 '14 at 13:30

arlistan

731
9
20

does this all go within the oncreate method? – Dominic Sewell Sep 17 '14 at 13:35
unfortunately this is showing "Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference" when i click – Dominic Sewell Sep 17 '14 at 13:54
when you click what ? – Selvin Sep 17 '14 at 13:57
2

From that error I can assume that something is missing in your activity, causing the ImageView to be null. I can't see a setContentView in your code, so maybe that is whats missing. – arlistan Sep 17 '14 at 13:59

Nabin · Answer 2 · 2014-09-17T13:48:37.567

0

Put your network task inside doInBackground() method of AsyncTask as follow:

@Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

try {
        //ImageView i = (ImageView)findViewById(R.id.imgView);Put this line in onPreExecute() method
        Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url).getContent());
       // i.setImageBitmap(bitmap);//and this one on postExecute() method
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

edited Sep 17 '14 at 13:48

answered Sep 17 '14 at 13:21

Nabin

11,216
8
63
98

@Selvin Please have a look and consider voting as well if you like :-) – Nabin Sep 17 '14 at 13:29
@Selvin sorry but couldn't understand the reason – Nabin Sep 17 '14 at 13:47
@SpiderMan this is life, things go up, and things go down. <3 – Munir Basheer Aug 13 '15 at 10:08

score 0 · Answer 3 · answered Sep 17 '14 at 13:47

0

Using Picasso after initializing yourImageView with findViewById();

Picasso.with(context).load(url).into(yourImageView)

answered Sep 17 '14 at 13:47

David Corsalini

7,958
8
41
66

How do I implement this image view in an async task?

3 Answers3

Linked

Related