使用CountDownTimer类轻松实现倒计时功能

CountDownTimer由系统提供
查资料的时候 发现了CountDownTimer这个类之后 果断抛弃了以前的倒计时做法

功能:
30秒倒计时 每次间隔1秒

参数:
mc.start();方法开始

mc.cancel();方法结束
new MyCountDownTimer(30000, 1000); 第一个参数表示 总的时间为30000毫秒,间隔1000毫秒

直接上代码:

package com.example.daojishi; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.os.CountDownTimer; 
import android.util.Log; 
import android.view.View; 
import android.widget.TextView; 
import android.widget.Toast; 
 
 
public class MainActivity extends Activity { 
 
  private MyCountDownTimer mc; 
  private TextView tv; 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    tv = (TextView) findViewById(R.id.show); 
    mc = new MyCountDownTimer(30000, 1000); 
    mc.start(); 
  } 
 
  public void oncancel(View view) { 
    Toast.makeText(MainActivity.this, "取消", Toast.LENGTH_LONG).show();// toast有显示时间延迟 
    mc.cancel(); 
  } 
 
  public void restart(View view) { 
    Toast.makeText(MainActivity.this, "重新开始", Toast.LENGTH_LONG).show();// toast有显示时间延迟 
    mc.start(); 
  } 
 
   
 
  class MyCountDownTimer extends CountDownTimer { 
     
    public MyCountDownTimer(long millisInFuture, long countDownInterval) { 
      super(millisInFuture, countDownInterval); 
    } 
 
    @Override 
    public void onFinish() { 
      tv.setText("done"); 
    } 
 
    @Override 
    public void onTick(long millisUntilFinished) { 
      Log.i("MainActivity", millisUntilFinished + ""); 
      tv.setText("倒计时(" + millisUntilFinished / 1000 + ")..."); 
    } 
  } 
} 
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//┃　　　┃  神兽保佑　　　　　　　　 
//┃　　　┃  代码无BUG！ 
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布局:

附:
CountDownTimer源码:

 
 
package android.os; 
 
import android.util.Log; 
 
 
public abstract class CountDownTimer { 
 
   
  private final long mMillisInFuture; 
 
   
  private final long mCountdownInterval; 
 
  private long mStopTimeInFuture; 
 
   
  public CountDownTimer(long millisInFuture, long countDownInterval) { 
    mMillisInFuture = millisInFuture; 
    mCountdownInterval = countDownInterval; 
  } 
 
   
  public final void cancel() { 
    mHandler.removeMessages(MSG); 
  } 
 
   
  public synchronized final CountDownTimer start() { 
    if (mMillisInFuture <= 0) { 
      onFinish(); 
      return this; 
    } 
    mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture; 
    mHandler.sendMessage(mHandler.obtainMessage(MSG)); 
    return this; 
  } 
 
 
   
  public abstract void onTick(long millisUntilFinished); 
 
   
  public abstract void onFinish(); 
 
 
  private static final int MSG = 1; 
 
 
  // handles counting down 
  private Handler mHandler = new Handler() { 
 
    @Override 
    public void handleMessage(Message msg) { 
 
      synchronized (CountDownTimer.this) { 
 final long millisLeft = mStopTimeInFuture - SystemClock.elapsedRealtime(); 
 
 if (millisLeft <= 0) { 
   onFinish(); 
 } else if (millisLeft < mCountdownInterval) { 
   // no tick, just delay until done 
   sendMessageDelayed(obtainMessage(MSG), millisLeft); 
 } else { 
   long lastTickStart = SystemClock.elapsedRealtime(); 
   onTick(millisLeft); 
 
   // take into account user's onTick taking time to execute 
   long delay = lastTickStart + mCountdownInterval - SystemClock.elapsedRealtime(); 
 
   // special case: user's onTick took more than interval to 
   // complete, skip to next interval 
   while (delay < 0) delay += mCountdownInterval; 
 
   sendMessageDelayed(obtainMessage(MSG), delay); 
 } 
      } 
    } 
  }; 
}