How to run a Runnable thread in Android?

The simple fix to your example is:

 

final Runnable r = new Runnable(){    public void run()     {        tv.append("Hello World");        handler.postDelayed(this, 1000);    }};handler.postDelayed(r, 1000);

Or we can use normal thread for example (with original Runner):

Thread thread = new Thread(){    @Override    public void run() {        try {            while(true) {                sleep(1000);                handler.post(r);            }        } catch (InterruptedException e) {            e.printStackTrace();        }    }};thread.start();

You may consider your runnable object just as a command that can be sent to the message queue for execution, and handler as just a helper object used to send that command.

More details are here http://developer.android.com/reference/android/os/Handler.html