android - 用新时间android重新启动倒数计时器

Question

我想在倒计时结束后以新的时间重新开始倒计时。我在下面给出代码:

futureInMillis = newTime();

            CountDownTimer remainingTimeCounter = new CountDownTimer(futureInMillis, 1000) {

            public void onTick(long millisUntilFinished) {
                remainingTime = calculateRemainingTime(millisUntilFinished / 1000);
                runOnUiThread(updateTime);
            }

            public void onFinish() {
                // TODO: restart counter
                cancel();
                futureInMillis = newTime();
//              remainingTimeCounter = null;
                this.start();
            }
        }.start();

Answer 1

我们应该知道 newTime() 做了什么，你不必调用方法 cancel() ，因为计时器在 onFinish() 方法，这意味着计时器完成倒计时:

CountDownTimer remainingTimeCounter = new CountDownTimer(futureInMillis, 1000) {

            public void onTick(long millisUntilFinished) {
                remainingTime = calculateRemainingTime(millisUntilFinished / 1000);
                runOnUiThread(updateTime);
            }

            public void onFinish() {
                // TODO: restart counter
                //cancel();  // there is no need the call the cancel() method here
                futureInMillis = newTime();
//              remainingTimeCounter = null;
                this.start();
            }
        }.start();

编辑:

CountDownTimer 类中没有可用于更改 futureInMillis 的属性，如果你想使用它，你应该使用两个 CountDownTimer；你应该创建两个类，每个类都有一个计时器和一个 futureInMillis 属性，然后当第一个类的计时器完成时，实例化第二个类，将 futureInMillis 传递给它，并启动她的计时器，反之亦然。

**EDIT 2 :**

或者简单地从源代码 android 中编辑类 CountDownTimer 的代码源，并为属性 futureInMillis 添加 setter 和 getter，如下所示:

/*
 * 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.
 */

//add your package declaration here

import android.util.Log;

/**
 * Schedule a countdown until a time in the future, with
 * regular notifications on intervals along the way.
 *
 * Example of showing a 30 second countdown in a text field:
 *
 * <pre class="prettyprint">
 * new CountdownTimer(30000, 1000) {
 *
 *     public void onTick(long millisUntilFinished) {
 *         mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
 *     }
 *
 *     public void onFinish() {
 *         mTextField.setText("done!");
 *     }
 *  }.start();
 * </pre>
 *
 * 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 MyCountDownTimer {

    /**
     * Millis since epoch when alarm should stop.
     */
    private long mMillisInFuture;

    /**
     * The interval in millis that the user receives callbacks
     */
    private long mCountdownInterval;

    private long mStopTimeInFuture;



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

    public void setMillisInFuture(long millisInFuture) {
        this.mMillisInFuture = millisInFuture;
    }

    public void setCountdownInterval(long countdownInterval) {
        this.mCountdownInterval = countDownInterval;
    }

    /**
     * Cancel the countdown.
     */
    public final void cancel() {
        mHandler.removeMessages(MSG);
    }

    /**
     * Start the countdown.
     */
    public synchronized final MyCountDownTimer start() {
        if (mMillisInFuture <= 0) {
            onFinish();
            return this;
        }
        mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture;
        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
    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {

            synchronized (MyCountDownTimer.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);
                }
            }
        }
    };
}

然后您可以像这样轻松更改 millisInFuture :

MyCountDownTimer remainingTimeCounter = new MyCountDownTimer(futureInMillis, 1000) {

                public void onTick(long millisUntilFinished) {
                    remainingTime = calculateRemainingTime(millisUntilFinished / 1000);
                    runOnUiThread(updateTime);
                }

                public void onFinish() {
                    // TODO: restart counter with millisInFuture = 4000 ( 4 seconds ) 
                    //cancel();  // there is no need the call the cancel() method here

                    this.setMillisInFuture(4000); // here we change the millisInFuture of our timer
                    this.start();
                }
            }.start();