How to clear CountDownTimer from onTick method?

Question

I have implemented the timer functionality in android app, I able to finish the timer from other local methods by calling timerObject.cancel() . Its working perfectly.

But when I tried to call same in onTick() method for specific condition, i am not able to cancel the timer, it last till the timer time ends.

How can i cancel the timer?

Answer 1

AFAIK You can not do that

But there is Drop-in alternative for the Android CountDownTimer class, but which you can cancel from within onTick.

Here you go

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

Answer 2

Looking at the source code for CountDownTimer it is easy to see why it is not working. cancel() merely removes the message for ticking the timer from the queue. But the message handler that gets called at each tick posts a message for the next tick after calling onTick(). So either you have to call cancel() outside of onTick(), via a Handler for example, or switch to using the Timer class instead.

Answer 3

if using RXJava2. this code can help you.

    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();
    } 
}

using:

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();
    } 
} 

the owner of the code https://gist.github.com/chemickypes/fa3b7fc5b5a00a3ce37fee5815018702