android Handler和Thread实现定时器开始计时和停止计时

package com.example.timer;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
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 {
private TextView timer;//显示时间的控件
private int recLen = 60;//定时长度
private Button startRec, stopRec;//控制开始计时和停止计时的按钮
private static final int START = 0;//开始计时消息标志，下面用到
private static final int STOP = 1;//停止计时消息标志，下面用到
private static int RUN = 0;//子线程中的while循环判断标志
private Thread thread;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

timer = (TextView) findViewById(R.id.timer);

startRec = (Button) findViewById(R.id.start);
stopRec = (Button) findViewById(R.id.stop);
startRec.setOnClickListener(listener);
stopRec.setOnClickListener(listener);

}

public OnClickListener listener = new OnClickListener() {

@Override
public void onClick(View v) {
int id = v.getId();
switch (id) {
case R.id.start:
RUN = 0;
thread = new Thread(new MyThread()); // start thread
thread.start();
break;
case R.id.stop:
//				long tid = thread.getId();
RUN = 1111;
thread.interrupt();
thread.run();
Message message = new Message();
message.what = STOP;
handler.sendMessage(message);
break;
default:
break;
}

}

};

@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;
}

final Handler handler = new Handler() { // handle
public void handleMessage(Message msg) {
switch (msg.what) {
case START:
recLen--;
timer.setText("" + recLen);
break;
case STOP:
timer.setText("" + recLen);
break;
}
super.handleMessage(msg);
}
};

public class MyThread implements Runnable { // thread
@Override
public void run() {
while (0 == RUN) {
try {
Thread.sleep(100); // sleep 100ms
Message message = new Message();
message.what = START;
handler.sendMessage(message);
} catch (Exception e) {
}
}
}
}

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<Button
android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="开始计时"
/>

<Button
android:id="@+id/stop"
android:layout_toRightOf="@id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="停止计时"
/>

<TextView
android:id="@+id/timer"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="25dp"
android:textColor="#FF0000"
android:text="@string/hello_world" />

</RelativeLayout>