Download an image into Bitmap file in android

Question

I've been trying to download an image into a bitmap element to load them into a gridView with images, but I need to do it async because if not gives the error "android.os.NetworkOnMainThreadException".

Searching I found a lot of tutorials to do that, but all of them add this element to an ImageView when finished. Is there any way to do that but into a Bitmap?

Here I have ways to download without async that I found:

URL url = new URL("http://....");
Bitmap image = BitmapFactory.decodeStream(url.openConnection().getInputStream());

One more:

public static Bitmap getBitmapFromURL(String src) {
    try {
        URL url = new URL(src);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream();
        Bitmap myBitmap = BitmapFactory.decodeStream(input);
        return myBitmap;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

Android load from URL to Bitmap

Put one of your code snippets in a thread to perform that work asynchronously. — CommonsWare, May 29 '16 at 13:24
https://docs.oracle.com/javase/tutorial/essential/concurrency/runthread.html http://tutorials.jenkov.com/java-concurrency/creating-and-starting-threads.html — CommonsWare, May 29 '16 at 13:41

Clive Seebregts · Accepted Answer · 2016-05-29T18:18:05.740

Wrap your getBitmapFromURL method into an AsyncTask, see below:

private class GetBitmapFromURLAsync extends AsyncTask<String, Void, Bitmap>   {
    @Override
    protected Bitmap doInBackground(String... params) {
        return getBitmapFromURL(params[0]);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
    }
}

Nest the above AsyncTask into your Activity:

public class MyActivity extends Activity {
  // To store the Bitmap returned by doInBackground asynctask
  private Bitmap result;
  // existing Activity code
  ...

  private class GetBitmapFromURLAsync extends AsyncTask<String, Void, Bitmap>   {
    @Override
    protected Bitmap doInBackground(String... params) {
      return getBitmapFromURL(params[0]);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
      //  return the bitmap by doInBackground and store in result
      result = bitmap;
    }
}

And to call the above code:

GetBitmapFromURLAsync getBitmapFromURLAsync = new GetBitmapFromURLAsync();
getBitmapFromURLAsync.execute("http://....");

But how can I do to return the bitmap? – Onelio May 29 '16 at 17:48 — Onelio, May 29 '16 at 17:48
I have added code to the answer on how to return the Bitmap – Clive Seebregts May 29 '16 at 18:20 — Clive Seebregts, May 29 '16 at 18:20

score 0 · Answer 2 · answered May 29 '16 at 16:50

You can't make heavy operations like http request from main (UI) thread in android. Or you will get that error. You can use AsyncTask.

class ImageDownloadTask extends AsyncTask<String, Void, Bitmap>   {

    //this operation is in backgrouund
    @Override
    protected Bitmap doInBackground(String... params) {
        return getBitmapFromURL(params[0]);
    }

    //operation is finished, update the UI with bitmap
    @Override
    protected void onPostExecute(Bitmap bitmap) {
    }
}

Or just use Picasso library, it does all work for you, including caching.

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

Download an image into Bitmap file in android

2 Answers2