package com.example.chronometerdemo; 
 
import android.os.Bundle; 
import android.os.SystemClock; 
import android.app.Activity; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Chronometer; 
import android.widget.Chronometer.OnChronometerTickListener; 
 
public class MainActivity extends Activity 
{ 
 Chronometer time=null; 
 Button restart=null; 
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.activity_main); 
   
  time=(Chronometer) findViewById(R.id.chronometer); 
  restart=(Button) findViewById(R.id.restart); 
   
  //设置起始时间和时间格式，然后开始计时 
  time.setBase(SystemClock.elapsedRealtime()); 
  time.setFormat("已用时间：%s"); 
  time.start(); 
   
  //给计时器添加监听器，当计时到达15s时，要重置 
  time.setOnChronometerTickListener(new OnChronometerTickListener() { 
    
   @Override 
   public void onChronometerTick(Chronometer arg0) 
   { 
    if(SystemClock.elapsedRealtime()-arg0.getBase()>=15000) 
    { 
     arg0.stop(); 
     restart.setVisibility(View.VISIBLE); 
    } 
     
   } 
  }); 
   
  //给按钮添加重置的效果 
  restart.setOnClickListener(new OnClickListener() { 
    
   @Override 
   public void onClick(View arg0) 
   { 
    time.setBase(SystemClock.elapsedRealtime()); 
    time.start(); 
    restart.setVisibility(View.GONE); 
     
   } 
  }); 
 } 
 
 
 @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; 
 } 
  
}