更新时间:2022-06-25 23:07:20
CountDownTimer(倒计时计数器)
0.本人写的综合案例
案例
说明及截图
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1.1介绍:
定时执行在一段时间后停止的倒计时,在倒计时执行过程中会在固定间隔时间得到通知。
1.2参数:
millisInFuture 从开始调用start()到倒计时完成并onFinish()方法被调用的毫秒数。(倒计时时间,单位毫秒)
countDownInterval 接收onTick(long)回调的间隔时间。(单位毫秒)
1.3公共方法
1.4使用方法
CountDownTimer timer = new CountDownTimer(30000, 1000) {
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
Intent intent = new Intent(GuideActivity.this, TimerReceiver.class);
intent.setAction("timer");
}
}.start();
源码分析
// handles counting down
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
synchronized (CountDownTimer.this) {
if (mCancelled) {
return;
}
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);
}
}
}
};
synchronized 关键字
主要有以下两个特点:
其他说明