如何清除CountDownTimer从onTick方法？

Question

我已经在android应用程序中实现了计时器功能，我可以通过调用timerObject从其他本地方法完成计时器。取消（）。它工作得很好。

但是，当我试图在onTick（）方法中为特定条件调用相同的函数时，我无法取消计时器，它将一直持续到计时器时间结束。

如何取消计时器？

Answer 1

如果使用RXJava2。这段代码可以帮助你。

    public abstract class CountDownTimer { 

    private TimeUnit timeUnit;
    private Long startValue;
    private Disposable disposable;

    public CountDownTimer(Long startValue,TimeUnit timeUnit) {
        this.timeUnit = timeUnit;
        this.startValue = startValue;
    } 

    public abstract void onTick(long tickValue);

    public abstract void onFinish(); 

    public void start(){ 
        io.reactivex.Observable.zip( 
                io.reactivex.Observable.range(0, startValue.intValue()), io.reactivex.Observable.interval(1, timeUnit), (integer, aLong) -> {
                    Long l = startValue-integer;
                    return l; 
                } 
        ).subscribeOn(Schedulers.io()) 
                .observeOn(AndroidSchedulers.mainThread()) 
                .subscribe(new Observer<Long>() { 
                    @Override 
                    public void onSubscribe(Disposable d) { 
                        disposable = d; 
                    } 

                    @Override 
                    public void onNext(Long aLong) { 
                        onTick(aLong); 
                    } 

                    @Override 
                    public void onError(Throwable e) { 
                        e.printStackTrace(); 
                    } 

                    @Override 
                    public void onComplete() { 
                        onFinish(); 
                    } 
                }); 
    } 

    public void cancel(){ 
        if(disposable!=null) disposable.dispose();
    } 
}

使用：

public class MainActivity extends AppCompatActivity { 

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.start_activity);

        new CountDownTimer(10L, TimeUnit.SECONDS) {

            @Override 
            public void onTick(long tickValue) {
                Log.d("CountDown", "Remaining: " + tickValue);

                // cancel();
            } 

            @Override 
            public void onFinish() { 
                Log.d("CountDown", "The End!! ");
            } 
        }.start();
    } 
} 

代码的所有者https://gist.github.com/chemickypes/fa3b7fc5b5a00a3ce37fee5815018702

Answer 2

查看CountDownTimer的源代码，很容易看出它不起作用的原因cancel（）仅从队列中删除用于勾选计时器的消息。但是在每次勾选时被调用的消息处理程序在调用onTick（）后为下一个勾选发布消息。因此，您必须在onTick（）之外通过处理程序调用cancel（），例如，或者切换到使用Timer类。

Answer 3

好吧，你不能那样做

但是Android CountDownTimer类还有一个替代方案，但是您可以在onTick中取消它。

干得好

/*
 * 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 alt.android.os;

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

/**
 * 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 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);
                    }
                }
            }
        }
    };
}