Java中断/停止计时器

Question

I have an if statement, that checks if my object (wizard) hit an item . If he did, the size of the wizard will change and he should be able to survive 1 collision with an obstacle.

Right now I'm stuck at "surviving 1 obstacle collision", because in my collision method I have set it up so that if InvulnerabilityActive is true, then it shouldn't detect collision.

So the problem is that, during the entire duration (9 seconds), no collision with an obstacle is being detected. The wizard just flies through. How can I change it, so that it doesn't detect collision with the first obstacle and then deactivates the item?

I thought of using the Timer.cancel() method, but as you can see I can only refer to it with the this keyword. I can't call Timer.cancel() before I use the Timer itself.

Here is the collision with the item.

try {
    invulnerability = new Rectangle(GameWorld.obstacle1.getX() - GameRenderer.generator2.getValue2(),
            GameWorld.obstacle1.getY() + GameRenderer.generator2.getValue1(), 15, 15);
    if ((Intersector.overlaps(GameWorld.wizard.getBoundingRectangle(), invulnerability))){
        GameRenderer.InvulnerabilityActive = true;
        activeItem = true;
        case0 = true; 
        GameWorld.wizard.setWidth(8);
        GameWorld.wizard.setHeight(8);
        new java.util.Timer().schedule(
                new java.util.TimerTask() {
                    public void run() {
                        this.cancel();
                        GameRenderer.InvulnerabilityActive = false;
                        activeItem = false;
                        case0 = false;
                        GameWorld.wizard.setWidth(16);
                        GameWorld.wizard.setHeight(16);
                    }
                 },
                 9000
        );
     }
} catch (NullPointerException e){
     System.out.println("Caught NullPointerException!");
}

Here's the collision with an obstacle method:

public boolean collides(Wizard wizard) {
   if (GameRenderer.InvulnerabilityActive){
       return false;
   } else {
       return (Intersector.overlaps(wizard.getBoundingRectangle(), barUp)
               || Intersector.overlaps(wizard.getBoundingRectangle(), barDown));
   }
}

I know that the problem is due to the if statement, because it just checks whether the item is active or not, but I don't know how to change it to make it work.

Answer 1

You need to check collisions first. If collision detected - check InvulnerabilityActive . If it is true - reset it to false and return false. On next collision InvulnerabilityActive will be false and collision will be detected.

public boolean collides(Wizard wizard) {
    if (Intersector.overlaps(wizard.getBoundingRectangle(), barUp)
            || Intersector.overlaps(wizard.getBoundingRectangle(), barDown)) {
        if (GameRenderer.InvulnerabilityActive) {
            GameRenderer.InvulnerabilityActive=false;
            return false;
        } else {
            return true;
        }
    } else {
        return false;
    }
}

There may be problem like "wizard flies through obstacle and collisions are constantly detected". In that case: add extra field bool InvulnerabilityActivePending to GameRenderer . Add GameRenderer.InvulnerabilityActivePending = true; next to GameRenderer.InvulnerabilityActive = true; . And use this code:

public boolean collides(Wizard wizard) {
    if (Intersector.overlaps(wizard.getBoundingRectangle(), barUp)
            || Intersector.overlaps(wizard.getBoundingRectangle(), barDown)) {
        if (GameRenderer.InvulnerabilityActive) {
            GameRenderer.InvulnerabilityActivePending=false;
            return false;
        } else {
            return true;
        }
    } else {
        GameRenderer.InvulnerabilityActive=GameRenderer.InvulnerabilityActivePending;
        return false;
    }
}

Instead of resetting InvulnerabilityActive on collision start, we reset it when collision ends.