android开发中动态获取系统时间

//主要使用子线程发送消息 使用Handler更新显示

import java.text.SimpleDateFormat;
import java.util.Date;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.widget.TextView;

public class MainActivity extends Activity  implements Runnable{
private Handler handler;
private TextView textView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textView=(TextView) findViewById(R.id.time);
handler = new Handler() {
public void handleMessage(Message msg) {
textView.setText((String)msg.obj);
}
};

new Thread(this).start();
}

@Override
public void run() {
// TODO Auto-generated method stub
try {
while(true){
SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日   HH:mm:ss");
String str=sdf.format(new Date());
handler.sendMessage(handler.obtainMessage(100,str));
Thread.sleep(1000);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}