VerificationCountDownTimer

認証コードを取得するときによく使われるコントロールは、ボタンをクリックすると60秒のカウントダウンが表示されます.実はこの原理は簡単で、textviewとTimerの混合使用です.
ダイレクトコード

  public class VerificationCountDownTimer extends CountDownTimer { 
    private final String text; 
    private final TextView view;    
    private  final  static  long MILLIS_IN_FUTURE=60000;//  60  
    private  final  static  long COUNT_DOWN_INTERVAL=1000;//1        
   /**     * @param millisInFuture    The number of millis in the future from the call     *                          to {@link #start()} until the countdown is done and {@link #onFinish()}     *                          is called.     * @param countDownInterval The interval along the way to receive     *                          {@link #onTick(long)} callbacks.     */   
    public VerificationCountDownTimer(long millisInFuture, long countDownInterval , TextView textView) {//        super(countDownInterval, millisInFuture);        super(MILLIS_IN_FUTURE, COUNT_DOWN_INTERVAL);   
           this.view = textView;      
           text = textView.getText().toString();   
   }  
    @Override  
    public void onFinish() {//         
      view.setText(text);   
       view.setClickable(true);  
    } 
     @Override  
     public void onTick(long millisUntilFinished) {     
           view.setClickable(false);//          
           view.setText(millisUntilFinished / COUNT_DOWN_INTERVAL + "     ");   
 }
}

使用時のみ

     verificationCountDown =  (TextView)findViewById(R.id.verificationCountDown);
     verificationCountDown.setOnClickListener(new View.OnClickListener() {   
     @Override    public void onClick(View v) { //0,0      
      new VerificationCountDownTimer(0,0,verificationCountDown); 
   }
});

簡単ではないでしょうか.では、CountDownTimerソースコードを見てみましょう.

public synchronized final CountDownTimer start() {  
mCancelled = false;    
if (mMillisInFuture <= 0) {   
     onFinish(); 
     return this;    
}   
  // SystemClock.elapsedRealtime()             
 mStopTimeInFuture = SystemClock.elapsedRealtime() +   mMillisInFuture;  
 mHandler.sendMessage(mHandler.obtainMessage(MSG));  
//     
 return this;

}
メッセージ処理をよく見て

 private Handler mHandler = new Handler() {   
 @Override
 public void handleMessage(Message msg) {   
     synchronized (CountDownTimer.this) {   
  //          
     if (mCancelled) {             
           return;           
     }         
  //           
     final long millisLeft = mStopTimeInFuture - SystemClock.elapsedRealtime();  
    // 0 ，    finish   
          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);   
         }     
     } 
   }
};