How to stop Handler Runnable?

Because you call postDelayed() again after removing call backs. Please use this code:

final Handler handler = new Handler();
final Runnable runnable = new Runnable() {
         public void run() {
               Log.d("Runnable","Handler is working");
               if(i == 5){ // just remove call backs
                    handler.removeCallbacks(this); 
                    Log.d("Runnable","ok");
                } else { // post again
                    i++;
                    handler.postDelayed(this, 5000); 
                }
       }
   };

//now somewhere in a method
 b1.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        handler.removeCallbacks(runnable); 
        handler.postDelayed(runnable, 5000); 
    }
});