Wrapper abstract class for Android's built-in AsyncTask with weak reference to target object. For example you can do any image processing in background (asynchronously) and set the output to a garbage collectible ImageView once completed. If for some reason the ImageView isn't available anymore (e.g. due to user switching activity), the `applyOu…

WeakTask.java

package net.akhyar.android.async;

import java.lang.ref.WeakReference;
import android.os.AsyncTask;

public abstract class WeakTask<I, O, T> extends AsyncTask<Void, Void, O> {
	protected final WeakReference<T> targetRef;
	protected I input;

	public WeakTask(I input, T target) {
		this.input = input;
		targetRef = new WeakReference<T>(target);
	}

	@Override
	protected O doInBackground(Void... args) {
		return process(input);
	}

	protected abstract O process(I input);

	@Override
	protected void onPostExecute(O output) {
		final T target = targetRef.get();
		if (target != null)
			applyOutputToTarget(output, target);
	}

	protected abstract void applyOutputToTarget(O output, T target);
}

Sample usage:

// decode file in background and set the result to an ImageView (weak referenced)
new WeakTask<String, Bitmap, ImageView>(path, imgPreview) {

    @Override
    protected Bitmap process(String path) {
        return BitmapFactory.decodeFile(path, null);
    }

    @Override
    protected void applyOutputToTarget(Bitmap result, ImageView target) {
        target.setImageBitmap(result);

        ............
    }
}.execute();