Java切换案例延迟

Question

I'm programming a little 2d game. Acutally I'm busy with the jumping-function. I want my player to jump, when i press the up-arrow key. I managed to make him jumping, but there is a delay of at least one second. This dealy is not existing for other actions like moving left or right. Do you know where it comes from?

The code for jumping is in the keyReaction method.

public class John<I> extends AbstractGame<I> {
//lists
List<ImageObject<I>> floor = new ArrayList<>();

//variables
double jumpHeight = 0;

//boolean
boolean jump = false;

//fix values
int blockHeight = 40;
int blockWidth = 40;

public John(double width, double height) {
    //getPlayer()
    super(new ImageObject<>("player.png", new Vertex(120, height - 200), new Vertex(0, 0)), width, height);

    //floor objects
    for(int i=0; i<getWidth(); i+=blockWidth)
        floor.add(new ImageObject<>("brick.png", new Vertex(i, getHeight() - blockHeight)));

    //add arrays to canvas
    getGOss().add(floor);
}

@Override
public void doChecks() {
    for(ImageObject<I> f:floor) {
        //gravity
        if(!(jump) && !(getPlayer().touches(f)))
            getPlayer().getMotion().y++;

        //stop y-motion on ground
        if(getPlayer().touches(f)){
            getPlayer().getPos().y = getHeight() - blockHeight - getPlayer().getHeight();
            getPlayer().getMotion().y = 0;}
    }
}

@Override
public boolean isStopped(){
    return false;
}

@Override
public void keyReaction(KeyCode keycode){
    switch (keycode) {
        //move left
        case LEFT_ARROW:
            getPlayer().getMotion().x = -2;
            break;
        case VK_A:
            getPlayer().getMotion().x = -2;
            break;
        //move right
        case RIGHT_ARROW:
            getPlayer().getMotion().x = 2;
            break;
        case VK_D:
            getPlayer().getMotion().x = 2;
            break;
        //jump
        case UP_ARROW:
            jump = true;
            if(jumpHeight < 100){
                jumpHeight += 5;
                getPlayer().getPos().y -=5;

            } else if (jumpHeight < 200){
                jumpHeight +=5;
                getPlayer().getPos().y +=5;
            }
            break;
        case VK_W:
            break;
        case SPACE:
            break;
    }
}

@Override
public void keyReactionReleased(KeyCode keycode){
    switch (keycode) {
        //move left
        case LEFT_ARROW:
            getPlayer().getMotion().x = 0;
            break;
        case VK_A:
            getPlayer().getMotion().x = 0;
            break;
        //move right
        case RIGHT_ARROW:
            getPlayer().getMotion().x = 0;
            break;
        case VK_D:
            getPlayer().getMotion().x = 0;
            break;
        //jump
        case UP_ARROW:
            jump = false;
            jumpHeight = 0;
            break;
        case VK_W:
            jump = false;
            break;
        case SPACE:
            break;
    }
}

//test main
public static void main(String[] args) {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.add(new SwingScreen(new John<>(1800, 600)));
    f.pack();
    f.setVisible(true);
}
}

Thank you for your help.

Code with the if:

case UP_ARROW:
    if(jumpHeight < 20){
        jumpHeight += 5;
        getPlayer().getPos().y = -5;

    } else if (jumpHeight < 40){
        jumpHeight +=5;
        getPlayer().getPos().y = 5;
    }
    break;

Code without the if:

case UP_ARROW:
   getPlayer().getPos().y = -5;
   break;

KeyReaction:

setOnKeyPressed((ev)->{
    logic.keyReaction(KeyCode.fromCode(ev.getCode().impl_getCode()));
    ev.consume();
        });

setOnKeyReleased((ev)->{
    logic.keyReactionReleased(KeyCode.fromCode(ev.getCode().impl_getCode()));
    ev.consume();
        });

Answer 1

In your jumpheight method you have

jump = true;
if(jumpHeight < 100){
  jumpHeight += 5;
  getPlayer().getPos().y -=5;
} else if (jumpHeight < 200){
  jumpHeight +=5;
  getPlayer().getPos().y +=5;
}
break;

On the 4th line there, you have a -=5 for the pos. There is likely another method that prevents the ypos from going under 0. What happens then is you press the up arrow, it gets sent 40 times(200/5), eventually the jumpheight is greater than 200, and only then does the player start moving up.