Slick2D中的java跳跃难度

Question

我研究了如何在slick2d中实现一个基本的重力系统。以下是我的代码（在更新函数中）：

if (input.isKeyDown(Input.KEY_UP)) {
        spressed = true; //Has the UP key been pressed?
    }
    if (spressed) { 
        if (!sjumping) {//if so, are we already in the air? 
             Sub_vertical_speed = -1.0f * delta;//negative value indicates an upward movement 
             sjumping = true;//yes, we are in the air
        }
        if (sjumping) { //if we're in the air, make gravity happen
             Sub_vertical_speed += 0.04f * delta;//change this value to alter gravity strength 
        } 
        Sub.y += Sub_vertical_speed;
    }
    if (Sub.y == Sub.bottom){//Sub.bottom is the floor of the game
        sjumping = false;//we're not jumping anymore
        spressed = false;//up key reset
    }

这就是问题所在。当我按下向上键时，精灵会跳跃并正常下降，但再次按下向上键不会产生任何效果。我最初认为这是因为我没有重置spressed，所以我添加了一行以将其设置为false，但您仍然只能跳转一次：/

Answer 1

看起来你的Sub.y需要夹在你的Sub.bottom上，这样它就不会超过它了。尝试：

if(Sub.y >= Sub.bottom) {
    Sub.y = Sub.bottom;
    sjumping = false;
    spressed = false;
}

Answer 2

我以前也做过类似的事情，我的假设是Sub.y永远不等于Sub.bottom。根据y位置和垂直速度的不同，对象的y位置永远不会恰好是Sub.bottom的值。下面的代码将对此进行测试：

if (Sub_vertical_speed + Sub.y > Sub.bottom){ //new position would be past the bottom
    Sub.y = Sub.bottom;
    sjumping = false; //we're not jumping anymore
    spressed = false; //up key reset
}