学习Android Handler消息传递机制

public final boolean sendMessage(Message msg) 
{ 
return sendMessageDelayed(msg, 0); 
} 
public final boolean sendEmptyMessage(int what)
{ 
return sendEmptyMessageDelayed(what, 0);
 
} 

public final boolean sendEmptyMessageDelayed(int what, long delayMillis) 
{ 
Message msg = Message.obtain();
msg.what = what; 
return sendMessageDelayed(msg, delayMillis); 
}

public class MainActivity extends Activity {
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 final TextView txt=(TextView)findViewById(R.id.showTime);
 final Handler myHandler=new Handler()
 {
  @Override
  public void handleMessage(Message msg)
  {
  if(msg.what==0x12)
  {

   txt.setText("当前时间:"+new java.util.Date());

  }
  }
 };
 Button btn=(Button)findViewById(R.id.btn);
 btn.setOnClickListener(new OnClickListener() {
  @Override
  public void onClick(View arg0) {
  // TODO Auto-generated method stub

  new Timer().schedule(new TimerTask() {
  @Override
   public void run() {
   // TODO Auto-generated method stub

   myHandler.sendEmptyMessage(0x12);
   }
  }, 0,1000);  
  }
 });

 }
 

 @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;
 }
 

}