public class TestActivity extends Activity{

private TextView mTextView;

private Handler mHandler;

@Override

protected void onCreate(Bundle savedInstanceState)

{

// TODO Auto-generated method stub

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

mHandler = new Handler();

mTextView = (TextView) findViewById(R.id.text);

mHandler.post(new Runnable() {

@Override

public void run()

{

// TODO Auto-generated method stub

mTextView.setText(String.valueOf((Math.random() * 100)));

mHandler.postDelayed(this, 2000);

}

});

}

}

main.xml中就是一个textview。

代码就是通过Handler不断把写textview的线程放到消息队列中，系统从消息队列获取消息后，就在UI线程绘制textview。