@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        init();
        Log.v ("gaurav", "Thread is : " + Thread.currentThread().getName());
        Task1 task = new Task1();
        task.execute();
    }

class Task1 extends AsyncTask {
    @Override
    protected Object doInBackground(Object... params) {
        // TODO Auto-generated method stub
        Log.v ("gaurav", "Thread task 1 is : " + Thread.currentThread().getName());

        Task2 task = new Task2();

        task.execute();
        return null;
    }
}

class Task2 extends AsyncTask {
    @Override
    protected Object doInBackground(Object... params) {
        // TODO Auto-generated method stub
        Log.v ("gaurav", "Thread task 2 is : " + Thread.currentThread().getName());

        Log.v ("gaurav", "Task 2 started");
        return null;
    }
}

> 08-07 09:46:25.564: V/gaurav(2100): Thread is : main 08-07
> 09:46:25.564: V/gaurav(2100): Thread task 1 is : AsyncTask #3 08-07
> 09:46:25.564: V/gaurav(2100): Thread task 2 is : AsyncTask #4 08-07
> 09:46:25.564: V/gaurav(2100): Task 2 started

class Task1 extends AsyncTask {
    @Override
    protected Object doInBackground(Object... params) {
        // TODO Auto-generated method stub
        Log.v ("gaurav", "Thread task 1 is : " + Thread.currentThread().getName());

        Task2 task = new Task2();
        task.execute();

        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        Log.v ("gaurav", "Log after sleeping");

        return null;
    }
}

class Task2 extends AsyncTask {
    @Override
    protected Object doInBackground(Object... params) {
        // TODO Auto-generated method stub
        Log.v ("gaurav", "Thread task 2 is : " + Thread.currentThread().getName());

        Log.v ("gaurav", "Task 2 Started");
        return null;
    }
}

08-07 06:13:44.208    3073-3073/testapplication V/gaurav﹕ Thread is : main
08-07 06:13:44.209    3073-3091/testapplication V/gaurav﹕ Thread task 1 is : AsyncTask #1
08-07 06:13:49.211    3073-3091/testapplication V/gaurav﹕ Log after sleeping
08-07 06:13:49.213    3073-3095/testapplication V/gaurav﹕ Thread task 2 is : AsyncTask #2
08-07 06:13:49.213    3073-3095/testapplication V/gaurav﹕ Task 2 Started

public synchronized void execute(final Runnable r) {
    mTasks.offer(new Runnable() {
        public void run() {
            try {
                r.run();
            } finally {
                scheduleNext();
            }
        }
    });
    if (mActive == null) {
        scheduleNext();
    }
}

protected synchronized void scheduleNext() {
    if ((mActive = mTasks.poll()) != null) {
        THREAD_POOL_EXECUTOR.execute(mActive);
    }
}

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    new Thread() {
        @Override
        public void run() {
            Task1 task = new Task1();
            task.execute();
        }
    }.start();
}

class Task1 extends AsyncTask {
    @Override
    protected Object doInBackground(Object... params) {
        return null;
    }
}

08-07 12:05:20.736      584-591/github.yaa110.testapplication E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-8
    java.lang.ExceptionInInitializerError
            at github.yaa110.testapplication.Main2Activity$1.run(Main2Activity.java:21)
     Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
            at android.os.Handler.<init>(Handler.java:121)
            at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
            at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
            at android.os.AsyncTask.<clinit>(AsyncTask.java:152)
            at github.yaa110.testapplication.Main2Activity$1.run(Main2Activity.java:21)

private final static String TAG = "ThreadingAsyncTask";
private ImageView mImageView;
private ProgressBar mProgressBar;
private int mDelay = 500;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mImageView = (ImageView) findViewById(R.id.imageView);;
    mProgressBar = (ProgressBar) findViewById(R.id.progressBar);

    final Button button = (Button) findViewById(R.id.loadButton);
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            new LoadIconTask().execute(R.drawable.cheetah);
        }
    });
    final Button otherButton = (Button) findViewById(R.id.otherButton);
    otherButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Toast.makeText(MainActivity.this, "I'm Working",
                    Toast.LENGTH_SHORT).show();
        }
    });
}


class LoadIconTask extends AsyncTask<Integer, Integer, Bitmap> {
    @Override
    protected void onPreExecute() {
        mProgressBar.setVisibility(ProgressBar.VISIBLE);
    }
    @Override
    protected Bitmap doInBackground(Integer... resId) {
        Bitmap tmp = BitmapFactory.decodeResource(getResources(), resId[0]);
        // simulating long-running operation
        for (int i = 1; i < 11; i++) {
            sleep();
            publishProgress(i * 10);
        }
        return tmp;
    }
    @Override
    protected void onProgressUpdate(Integer... values) {
        mProgressBar.setProgress(values[0]);
    }
    @Override
    protected void onPostExecute(Bitmap result) {
        mProgressBar.setVisibility(ProgressBar.INVISIBLE);
        mImageView.setImageBitmap(result);
    }
    private void sleep() {
        try {
            Thread.sleep(mDelay);
        } catch (InterruptedException e) {
            Log.e(TAG, e.toString());
        }
    }
}