<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 android:layout_width="fill_parent" 
 android:layout_height="fill_parent" 
 android:orientation="vertical" > 
 
 <Chronometer 
 android:id="@+id/myChronometer" 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" /> 
 
 <LinearLayout 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:orientation="horizontal" > 
 
 <Button 
  android:id="@+id/btnStart" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="开始计时" /> 
 
 <Button 
  android:id="@+id/btnStop" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="停止" /> 
 
 <Button 
  android:id="@+id/btnBase" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="复位" /> 
 
 <Button 
  android:id="@+id/btnFormat" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="格式化" /> 
 </LinearLayout> 
 
</LinearLayout> 

package com.example.timer; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.os.SystemClock; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Chronometer; 
 
public class MainActivity extends Activity { 
 private Chronometer myChronometer = null; 
 private Button btnStart = null; 
 private Button btnStop = null; 
 private Button btnBase = null; 
 private Button btnFormat = null; 
 
 public void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); // 生命周期方法 
 super.setContentView(R.layout.activity_main); // 设置要使用的布局管理器 
 this.myChronometer = (Chronometer) super 
  .findViewById(R.id.myChronometer); 
 btnStart = (Button) super.findViewById(R.id.btnStart); 
 btnStop = (Button) super.findViewById(R.id.btnStop); 
 btnBase = (Button) super.findViewById(R.id.btnBase); 
 btnFormat = (Button) super.findViewById(R.id.btnFormat); 
 btnStart.setOnClickListener(new OnClickListenerStart()); 
 btnStop.setOnClickListener(new OnClickListenerStop()); 
 btnBase.setOnClickListener(new OnClickListenerBase()); 
 btnFormat.setOnClickListener(new OnClickListenerFormat()); 
 } 
 
 private class OnClickListenerStart implements OnClickListener { 
 
 public void onClick(View arg0) { 
  myChronometer.start(); 
 
 } 
 
 } 
 
 private class OnClickListenerStop implements OnClickListener { 
 
 public void onClick(View arg0) { 
  myChronometer.stop(); 
 
 } 
 
 } 
 
 private class OnClickListenerBase implements OnClickListener { 
 
 public void onClick(View arg0) { 
  myChronometer.setBase(SystemClock.elapsedRealtime()); 
 
 } 
 
 } 
 
 private class OnClickListenerFormat implements OnClickListener { 
 
 public void onClick(View arg0) { 
  myChronometer.setFormat("新的显示格式：%s。"); 
 
 } 
 
 } 
 
}