<?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="開始計時" />   <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="復(fù)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); // 設(shè)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("新的顯示格式：%s。");   }   }  }