如何制作减少数值的函数（例如，从800毫秒减少到200毫秒）

Question

the timer is set in a period of 800 milliseconds, so always RandomPositions() will execute the inner code every 800 milliseconds (the period). Now, what I want is to decrease this number by 50 every 20 seconds or 20,000 milliseconds until it gets the period to 200 milliseconds.

GOAL - IN THE GAME THIS MUST BE INCREASING THE SPEED GRADUALLY EVERY 20 SECONDS.

example: first execution - 800 milliseconds, second execution - 750 milliseconds, third execution - 700 milliseconds, and so on...

What I think is that I could insert a function of type Integer (instead of 800), that can make this job of decreasing from 800 to 200 miliseconds.

How can I make this function? or is there any other solution?

public void RandomPositions() {

        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask()
        {
            public void run() {

                getWindowManager().getDefaultDisplay().getMetrics(displaymatrics);
                float dx = r.nextFloat() * displaymatrics.widthPixels/1.2f;
                float dy = r.nextFloat() * displaymatrics.heightPixels/1.2f;
                button.animate().x(dx).y(dy).setDuration(0);


            }
        }, 0, 800);  // first value = Delay   , Second value = Period(what I need to change)

Answer 1

I wouldn't use a Timer for that, as the interval changes all the time.

In vanilla Android I would probably use a Handler

Int interval = 800; // milliseconds
Handler handler = new Handler()
Runnable runnable = new Runnable() { 

   @Override void run() {

        //
        // do your logic here
        //

        // decrement interval by 20 milliseconds 
        // if interval - 20 is greater than 200
        interval = interval - 20 > 200 ? interval - 20 : interval;


        // Request an execution of this runnable with the new value of interval
        handler.postDelayed(runnable, interval);
   }
}


public void start() {
   handler.postDelayed(runnable, interval);
}

public void stop() { 
   handler.removeCallbacks(runnable);
}

Make sure you call removeCallbacks whenever you want to stop it, or whenever the user is leaving the activity/context where this is running.

Answer 2

Here's a solution that uses a timer. If you don't want to call the method in a loop then just subtract the delay parameter by 50 each time you call it.

    public static void main(String[] args) {                
        Timer timer = new Timer();              
        for(int i = 800; i >= 200; i-=50)
        {
            runTimer(timer, i);         
        }   
    }   

    private static void runTimer(Timer timer, int delay) {
        timer.schedule(new TimerTask()
        {
            public void run() {
            }                
        }, 0, delay);  
    }