CODEWITHSUNDEEP
animationlibgdx
Vilda
Vilda

Reputation: 1793

StateTime in LibGDX Animation

How do I use implemented Animation in LibGDX? I know, that the documentation can be found here, but when I want to get a frame out of the Animation, I need to use stateTime, which isn't explained anywhere in the documentation. So the question is, what is stateTime in terms of LibGDX's Animation?

Upvotes: 4

Views: 2357

Answers (2)

David Martin
David Martin

Reputation: 29

animationFrames = walkSheetArray[moveDirection];
animation = new Animation(1f / 5f, animationFrames);
myAnimatedActor = new AnimatedActor(animation);
stage.addActor(myAnimatedActor);

public class AnimatedActor extends Image {
    private float stateTime = 0;
    Animation animation;
    public AnimatedActor(Animation animation) {
        super(animation.getKeyFrame(0));
        this.animation = animation;
    }

    @Override
    public void act(float delta) {
        ((TextureRegionDrawable) getDrawable()).setRegion(animation.getKeyFrame(stateTime += delta, true));
        super.act(delta);
    }
}

Upvotes: 0

P.T.
P.T.

Reputation: 25177

There is some more doc on the getKeyFrame method documentation:

Returns a TextureRegion based on the so called state time. This is the amount of seconds an object has spent in the state this Animation instance represents, e.g. running, jumping and so on.

(This documentation doesn't really make any sense to me either.)

But, the Animation.java source is readable. It looks like it boils down to getKeyFrameIndex which divides the stateTime by frameDuration (which is a parameter of the constructor -- how long each frame lasts) to compute an array index. getKeyFrameIndex does different things for looping or non-looping sequences, but basically it takes the array index to look up the right key frame in the sequence to display.

So the "stateTime" is the input to pick a key frame from your Animation. The documentation is assuming you have one Animation instance for "running" and another for "jumping" (these are the "states" its referring to). To find the right key frame within an Animation, you tell it how long you've been in this "state". So, if you've been in the "running" Animation instance for 1.2 seconds, it does some math to figure out which key frame to show (say you've initialized the instance with 30 frames that show for 0.0333 seconds and loop -- it picks the 6th frame).

The wiki https://github.com/libgdx/libgdx/wiki/2D-Animation has some more details and an example, but doesn't address this directly, either.

Upvotes: 3

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