Android系统里的倒计时工具CountDownTimer无法cancle的解决方法

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前几天用到了一个倒计时的工具android.os.CountDownTimer,但是其cancle方法竟然无效,蛋疼。
网上查了下,都遇到了这个问题。。。

下面是github上有人重写的一个CountDownTimer工具,可以完美cancle:

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import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;

/* The calls to {@link #onTick(long)} are synchronized to this object so that
* one call to {@link #onTick(long)} won't ever occur before the previous
* callback is complete. This is only relevant when the implementation of
* {@link #onTick(long)} takes an amount of time to execute that is significant
* compared to the countdown interval.
*/

public abstract class CountDownTimer {

/**
* Millis since epoch when alarm should stop.
*/

private final long mMillisInFuture;

/**
* The interval in millis that the user receives callbacks
*/

private final long mCountdownInterval;

private long mStopTimeInFuture;

private boolean mCancelled = false;

/**
* @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 CountDownTimer(long millisInFuture, long countDownInterval) {
mMillisInFuture = millisInFuture;
mCountdownInterval = countDownInterval;
}

/**
* Cancel the countdown.
*
* Do not call it from inside CountDownTimer threads
*/

public final void cancel() {
mHandler.removeMessages(MSG);
mCancelled = true;
}

/**
* Start the countdown.
*/

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


/**
* Callback fired on regular interval.
* @param millisUntilFinished The amount of time until finished.
*/

public abstract void onTick(long millisUntilFinished);

/**
* Callback fired when the time is up.
*/

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;

if (!mCancelled) {
sendMessageDelayed(obtainMessage(MSG), delay);
}
}
}
}
};
}

官方api里的栗子:

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new CountDownTimer(30000, 1000) {

public void onTick(long millisUntilFinished) {
mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
}

public void onFinish() {
mTextField.setText("done!");
}
}.start();

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