Android实战教程第四十篇之Chronometer实现倒计时

<?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。"); 
 
 } 
 
 } 
 
}