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

Answer 1

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://....");

Answer 2

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);