Pause a loop with CountDownTimer methods until the methods are completed

Question

I'm trying to create an app that mimics a traffic light by looping a segment of code that switches the background of a TextView from red to yellow to green after holding each color for a certain amount of time. The user will be able to start and end the loop by pressing a button. I've used CountDownTimers to hold each background of the TextView for a certain amount of time, and that method seems to be working fine. The current state of my code is as follows:

    public void trafficLight() {
        lightDisplay.setBackgroundColor(Color.RED);

        // Temporary for loop, a do-while loop causes the app to crash
        for (int x = 2; x <= 4; x++) {
             signalSwitcher(3000, Color.YELLOW);
             signalSwitcher(6000, Color.GREEN);
             signalSwitcher(9000, Color.RED);
        }
    }


    public void signalSwitcher(long delayTime, final int signalColor) {
        new CountDownTimer(delayTime, 1000) {

            @Override
            public void onTick(long millisUntilFinished) {
            }

            @Override
            public void onFinish() {
                lightDisplay.setBackgroundColor(signalColor);
            }

        }.start();

I can't seem to get the code in the trafficLight method to loop, as I haven't found a way to pause the start of another loop iteration before the background change cycle completes. In other words, when I run the code, the loop keeps scheduling the tasks in the CountDownTimers; it doesn't schedule, wait for the tasks to complete, and repeat.

My best attempt at trying to solve this problem consisted of having another do-while loop at the end of the signalSwitcher methods that rechecks a parameter until the last signalSwitcher method provides the input needed to exit that loop. However, it seems that this method doesn't work, as I get a blank screen when I try to run the app.

Simply stated, how can you pause a loop until the code inside CountDownTimers are executed?

Answer 1

I think there is no direct api can pause and resume the timer. But you can just cancel it, then record the remaining time. Recreate a timer with the remaining time.

Answer 2

Instead of for loop, do the changes in CountDownTimer onTick() method. Try with this code.

public void trafficLight() {
    lightDisplay.setBackgroundColor(Color.RED);        
    signalSwitcher(9000);
}


public void signalSwitcher(long delayTime) {
    new CountDownTimer(delayTime, 1000) {

        @Override
        public void onTick(long millisUntilFinished) {
    if(millisUntilFinished == 3000)
        lightDisplay.setBackgroundColor(Color.YELLOW);
    else if(millisUntilFinished == 6000)
        lightDisplay.setBackgroundColor(Color.GREEN);

        }

        @Override
        public void onFinish() {
           lightDisplay.setBackgroundColor(Color.RED);
        }

    }.start();