ActivityDestroyObserver.java

import android.app.Activity;

public interface ActivityDestroyObserver {

	public void registerOnDestroy(ActivityEndAction action);

	public Activity getActivity();
}

ActivityEndAction,java

import android.content.Context;

public interface ActivityEndAction {

	public void execute(Context context);
}

AsyncImageDownloader .java

package com.mcall.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.MalformedURLException;
import java.net.URL;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;


public class AsyncImageDownloader extends AsyncTask<Void, Void, Drawable> {

	private WeakReference<ImageView> _reference;
	private String _name;
	private String _url;
	private ActivityDestroyObserver _context;
	private boolean _save;
	private Bitmap bm;
	private boolean destroy = false;
	private boolean fullsize = false;
	
	private int thumbsize = 100;
	
	public AsyncImageDownloader(ActivityDestroyObserver context, String name, ImageView iv, String url) {
		this(context, name, iv, url, false);
	}
	
	
	public AsyncImageDownloader setThumbsize(int size){
		thumbsize = size;
		return this;
	}
	public AsyncImageDownloader setFullSize(boolean size){
		fullsize = size;
		return this;
	}

	public AsyncImageDownloader(ActivityDestroyObserver context, String name, ImageView iv, String url, boolean save) {
		_name = name;
		_url = url;
		_reference = new WeakReference<ImageView>(iv);
		_save = save;
		_context = context;

		context.registerOnDestroy(new ActivityEndAction() {
			public void execute(Context context) {
				destroy = true;
				if (bm != null) {
					bm.recycle();
				}
				_reference.clear();
				_reference = null;
				bm = null;
				_context = null;
				_name = null;
				
			}
		});
	}

	protected Drawable doInBackground(Void... params) {
		if (_reference != null && _reference.get() != null && !destroy) {

			String file = FileUtil.getFilePath("cache/image_download/" + _name);
			if (new File(file).exists()) {
				return decodeFileToDrawable(file);
			}

			URL url;
			try {
				url = new URL(_url);
				InputStream content = (InputStream) url.getContent();

				FileUtil.createFolders("cache/image_download/");
				FileUtil.saveTo(file, content);
				Drawable dw = decodeFileToDrawable(file);
				if (!_save) {
					new File(file).delete();
				}
				return dw;

			} catch (MalformedURLException e) {
			} catch (IOException e) {
			}
		}
		return null;
	}

	private Drawable decodeFileToDrawable(String f) {
		if (_context == null){
			return null;
		}
		if(_context.getActivity() == null){
			return null;
		}
		return new BitmapDrawable(_context.getActivity().getResources(), decodeFile(new File(f)));
	}

	// decodes image and scales it to reduce memory consumption
	private Bitmap decodeFile(File is) {
		// Decode image size
		try {
			
			
			BitmapFactory.Options o = new BitmapFactory.Options();
			o.inJustDecodeBounds = true;
			BitmapFactory.decodeStream(new FileInputStream(is), null, o);
			
			
			// The new size we want to scale to
			final int REQUIRED_SIZE = this.fullsize ? 1024 : thumbsize;

			// Find the correct scale value. It should be the power of 2.
			int scale = 1;
			while (o.outWidth / scale / 2 >= REQUIRED_SIZE && o.outHeight / scale / 2 >= REQUIRED_SIZE)
				scale *= 2;

			// Decode with inSampleSize
			BitmapFactory.Options o2 = new BitmapFactory.Options();
			o2.inSampleSize = scale;
			this.bm = BitmapFactory.decodeStream(new FileInputStream(is), null, o2);
			return this.bm;
		} catch (FileNotFoundException e) {
			Log.e("error", "File not found:" + is.getAbsolutePath(), e);
			return null;
		}
	}

	protected void onPostExecute(Drawable result) {
		super.onPostExecute(result);
		if (_reference != null && _reference.get() != null) {
			_reference.get().setImageDrawable(result);
		}
	}

}

BaseActivity.java

public class BaseActivity extends Activity implements ActivityDestroyObserver{
	private List<ActivityEndAction> actions;

	@Override
	public void registerOnDestroy(ActivityEndAction action) {
		if (actions == null)
			actions = new ArrayList<ActivityEndAction>();
		actions.add(action);
	}

	protected void onDestroy() {
		super.onDestroy();
		if (actions != null) {
			for (ActivityEndAction action : actions) {
				try {
					action.execute(this);
				} catch (Exception ex) {
					Log.e("error", "error", ex);
				}
			}
			actions.clear();
			actions = null;
		}
	}

	@Override
	public Activity getActivity() {
		return this;
	}
}

MyActivity

import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;



public class MyActivity extends BaseActivity {

	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		// TODO: implement left guester
		setContentView(R.layout.activity_image);
		Bundle extras = getIntent().getExtras();

		String title = extras.getString("Title");
		String url = extras.getString("Url");
		String name = extras.getString("Name");

		final ImageView imageview = (ImageView) _findViewById(R.id.image_imageview);
		new AsyncImageDownloader(ImageActivity.this, name == null ? "image" : name, imageview, url, name != null)
				.setFullSize(true).execute();

	}
}