Android – Setting a downloaded image to an ImageView

Setting an ImageView with a downloaded image is a fairly common thing to do in Android and there are plenty of tutorials out there for doing just this but I’m going to do something a little different. I’m going to extend an ImageView and have the ImageView take care of the downloading and setting the bitmap.

**Note: remember to set the internet permission in the manifest

When declaring a custom view in xml you need to specify the full package name, see below.

<!--?xml version="1.0" encoding="utf-8"?-->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<com.custom.image.CustomImageView android:id="@+id/image"
		android:layout_width="fill_parent" android:layout_height="fill_parent"/>
</LinearLayout>

Here is the custom ImageView, nothing too complex, all you need is a constructor, an AsyncTask to download the image and a method to start the AsyncTask.

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.AttributeSet;
import android.widget.ImageView;

public class CustomImageView extends ImageView {
	//constructor
	public CustomImageView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}
	
	/**
	 * method to start the download
	 * @param url - the url of the image to download
	 */
	public void downloadImage(String url){
		new GetImage().execute(url);
	}
	/**
	 * AsyncTask to download the image in the background
	 * The downloaded bitmap is passed to the onPostExecute and 
	 * the ImageView sets the bitmap there (back in the UI thread)
	 *
	 */
	private class GetImage extends AsyncTask<String,Void,Bitmap>{

		@Override
		protected Bitmap doInBackground(String... params) {

			try {

				return BitmapFactory.decodeStream((InputStream)new URL(params[0]).getContent());
			} catch (MalformedURLException e) {
				e.printStackTrace();

			} catch (IOException e) {
				e.printStackTrace();

			}

			return null;

		}
		@Override
		protected void onPostExecute(Bitmap b){
			if(b != null)
				setImageBitmap(b);
		}
	}
}

And finally the main Activity.

public class CustomImageViewActivity extends Activity {

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
        //get the custom image view
		CustomImageView image = (CustomImageView)findViewById(R.id.image);
        //start the download
		image.downloadImage("http://cdn.esphoneblog.com/wp-content/uploads/2011/12/android-logo-font.png");
		
	}
}

And that is it, a nice clean way to download and set an image.