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CountDownTimerCopyFromAPI25.java
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CountDownTimerCopyFromAPI25.java
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/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cn.dawnyu.demo.androidnotedemo.countdown;
import android.annotation.SuppressLint;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.util.Log;
/**
* Schedule a countdown until a time in the future, with
* regular notifications on intervals along the way.
* <p>
* Example of showing a 30 second countdown in a text field:
* <p>
* <pre class="prettyprint">
* new CountDownTimer(30000, 1000) {
* <p>
* public void onTick(long millisUntilFinished) {
* mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
* }
* <p>
* public void onFinish() {
* mTextField.setText("done!");
* }
* }.start();
* </pre>
* <p>
* 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.
*/
/**
* Copy from API 25 's CountDownTimer.
* API 25 CountDownTimer 的源码副本。
* 仅增加了中文注释和 Log 打印代码。(注释为 Add 的代码)
* <p>
* date 2018/1/9
*/
public abstract class CountDownTimerCopyFromAPI25 {
private String TAG = "CountDownTimer-25";//Add
/**
* 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;
/**
* boolean representing if the timer was cancelled
*/
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 CountDownTimerCopyFromAPI25(long millisInFuture, long countDownInterval) {
mMillisInFuture = millisInFuture;
mCountdownInterval = countDownInterval;
}
/**
* Cancel the countdown.
*/
public synchronized final void cancel() {
mCancelled = true;
mHandler.removeMessages(MSG);
}
/**
* Start the countdown.
*/
public synchronized final CountDownTimerCopyFromAPI25 start() {
mCancelled = false;
if (mMillisInFuture <= 0) {
onFinish();
return this;
}
//Add
Log.i(TAG, "start → mMillisInFuture = " + mMillisInFuture + ", seconds = " + mMillisInFuture / 1000);
mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture;
//Add
Log.i(TAG, "start → elapsedRealtime = " + SystemClock.elapsedRealtime());
Log.i(TAG, "start → mStopTimeInFuture = " + mStopTimeInFuture);
mHandler.sendMessage(mHandler.obtainMessage(MSG));
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
@SuppressLint("HandlerLeak")
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
synchronized (CountDownTimerCopyFromAPI25.this) {
if (mCancelled) {
return;
}
final long millisLeft = mStopTimeInFuture - SystemClock.elapsedRealtime();
//Add
Log.i(TAG, "handleMessage → elapsedRealtime = " + SystemClock.elapsedRealtime());
Log.i(TAG, "handleMessage → millisLeft = " + millisLeft + ", seconds = " + millisLeft / 1000);
if (millisLeft <= 0) {
//Add
Log.i(TAG, "onFinish → millisLeft = " + millisLeft);
onFinish();
} else if (millisLeft < mCountdownInterval) {
//Add
Log.i(TAG, "handleMessage → millisLeft < mCountdownInterval !");
// no tick, just delay until done
//不执行 onTick(),直接延迟直到计时结束
sendMessageDelayed(obtainMessage(MSG), millisLeft);
} else {
long lastTickStart = SystemClock.elapsedRealtime();
//Add
Log.i(TAG, "before onTick → lastTickStart = " + lastTickStart);
Log.i(TAG, "before onTick → millisLeft = " + millisLeft + ", seconds = " + millisLeft / 1000);
onTick(millisLeft);
//Add
Log.i(TAG, "after onTick → elapsedRealtime = " + SystemClock.elapsedRealtime());
// take into account user's onTick taking time to execute
// 考虑到用户执行 onTick 需要时间
long delay = lastTickStart + mCountdownInterval - SystemClock.elapsedRealtime();
//Add
Log.i(TAG, "after onTick → delay1 = " + delay);
// special case: user's onTick took more than interval to
// complete, skip to next interval
// 特殊情况:用户的 onTick 执行时间超过了给定的时间间隔 mCountdownInterval,则直接跳到下一次间隔
while (delay < 0) delay += mCountdownInterval;
//Add
Log.i(TAG, "after onTick → delay2 = " + delay);
sendMessageDelayed(obtainMessage(MSG), delay);
}
}
}
};
}