Android and TimerTask (Java)

package com.myapp;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;

import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;

public class MainActivity extends Activity {

	Handler handler = new Handler();
	Timer timer = new Timer();	
	TimerTask timetask;
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);	

		
		// btnStart
		final Button btnStart = (Button) findViewById(R.id.btnStart);
		// Perform action on click
		btnStart.setOnClickListener(new View.OnClickListener() {
			public void onClick(View v) {
				// TODO Auto-generated method stub
				doTask();
			}
		});
		
		// btnStop
		final Button btnStop = (Button) findViewById(R.id.btnStop);
		// Perform action on click
		btnStop.setOnClickListener(new View.OnClickListener() {
			public void onClick(View v) {
				// TODO Auto-generated method stub
				stopTask();
			}
		});

	}

    public void doTask(){
    	 
    	timetask = new TimerTask() {
    	        public void run() {
    	                handler.post(new Runnable() {
    	                        public void run() {
 
    	                			Calendar c = Calendar.getInstance();
    	                			SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    	                			String formattedDate = df.format(c.getTime());

    	                	        // txtResult
    	                	        TextView result = (TextView) findViewById(R.id.txtResult);
    	                	        result.setText("TimeTask runing... Current : " + formattedDate);
    	                        }
    	               });
    	        }};
    	        timer.schedule(timetask, 0, 1000); // Every 1 second

    	 }
    
    public void stopTask(){
    	if(timetask != null)
    	{
    		timetask.cancel();
 	        TextView result = (TextView) findViewById(R.id.txtResult);
	        result.setText("TimeTask stop.");
    	}
    }

}