handler thread

package com.example.handlerdemo;

import java.util.Date;

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

public class MainActivity extends Activity {
	Handler handler;
	Button start,end;
	TextView tv;
	Runnable r;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		tv=(TextView)this.findViewById(R.id.textView1);
		start=(Button)this.findViewById(R.id.start);
		end=(Button)this.findViewById(R.id.end);
		handler=new Handler();
		r = new Runnable(){
			@Override
			public void run(){
				tv.setText(new Date().toString());
				handler.postDelayed(r, 1000);
			}
		};
		start.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v){
				handler.post(r);
			}
			
		});
		
		end.setOnClickListener(new OnClickListener(){
			@Override
			public void onClick(View v){
				handler.removeCallbacks(r);
			}
		});
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}