How do I add a timer in libgdx java?

问题:

I am trying to add a timer for power ups in my game. What I am trying to do is change a parameter (like jump height for example) after the player has collided with the power up box but it should only apply for 4 seconds. I have already written the collision coding and have added a random element to choose which power up is activated. I have also added a power up that will not use the timer (adding 1 to the score).

Searching google I found code using various methods like Gdx.graphics.getDeltaTime() and Timer.schedule but I can't seem to get them to work, maybe I am coding them incorrectly. I've been trying to use code like this but when using System.out.println(timeSinceCollision), I keep getting a constant value every time and it doesn't seem to be increasing.

float timeSinceCollision = 0;
timeSinceCollision += delta;
if(timeSinceCollision < 4f) {
 // the action
} else {
 // reset

}

回答1:

As I mentioned in my comment above, you can use the CountDownTimer class.

new CountDownTimer(4000, 4000) {
    public void onTick(long millisUntilFinished) {

    }

    public void onFinish() {
       isPoweredUp = false;
    }
}.start();

回答2:

You are creating timeSinceCollision every time with value of 0 thats why it never increase.

Take a look at my function. the If condition will be true every 4 seconds.

    final float TIME_SINCE_COLLISION = 4;
    float timeSinceCollision = 0;

    public void update(float delta) {

        timeSinceCollision += delta;
        if (timeSinceCollision >= TIME_SINCE_COLLISION) {
            timeSinceCollision -= TIME_SINCE_COLLISION;
            // Do something after 4 seconds.
            Gdx.app.log("Do something", "");
        }
    }