Question

我无法弄清楚如何使用up-key使myGamePiece跳转。首先，我尝试了简单的“myGamePiece.speedY = 1”，但这不起作用。也没有尝试在函数中反转“this.gravitySpeed”。有人可以帮助我，如果可能的话解释为什么我的不工作而你的工作呢？提前致谢！我的借口如果似乎很长，我无法在不删除组件代码的情况下进一步缩短它。

对代码的解释：

function startGame：开始游戏

var myGameArea：允许乘以两个键

功能组件：生成对象及其特征

function updateGameArea：允许移动对象

    <!DOCTYPE html>
    <html>
    <head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <style>
    canvas {
        border:1px solid #d3d3d3;
        background-color: #f1f1f1;
    }
    </style>
    </head>
    <body onload="startGame()">
    <script>
    var myGamePiece;

function startGame() {
    myGamePiece = new component(30, 30, "red", 80, 75);
    myGameArea.start();
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);
        window.addEventListener('keydown', function (e) {
            myGameArea.keys = (myGameArea.keys || []);
            myGameArea.keys[e.keyCode] = true;
        })
        window.addEventListener('keyup', function (e) {
            myGameArea.keys[e.keyCode] = false; 
        })
    }, 
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y, type) {
    this.width = width;
    this.height = height;
    this.x = x;
    this.y = y;    
    this.gravity = 0.05;
    this.gravitySpeed = 0;
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.gravitySpeed += this.gravity;
        this.x += this.speedX;
        this.y += this.speedY + this.gravitySpeed;
        this.hitBottom();
    }
    this.hitBottom = function() {
        var rockbottom = myGameArea.canvas.height - this.height;
        if (this.y > rockbottom) {
            this.y = rockbottom;
        }
    }
}

function updateGameArea() {
myGameArea.clear();
    myGamePiece.speedX = 0;
    myGamePiece.speedY = 0; 
    if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedX = -2; }
    if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedX = 2; }
    if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speedY = -1; }
    if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speedY = 1; }
    myGamePiece.newPos(); 
    myGamePiece.update();
}
    </script>

    </body>
    </html>

Answer 1

问题是gravitySpeed变量的值不断增加。

尝试在gravitySpeed支票中将hitBottom变量值重置为0：

if (this.y > rockbottom) {
    this.y = rockbottom;
    this.gravitySpeed = 0;
}

您可能还希望在调试时实时查看某些参数的值：

将这样的块添加到您的html中

<div style="position:absolute; width: 300px; bottom: 50px; right: 50px;">
    <p>sppedY: <span id="speedY"></span></p>
    <p>gravitySpeed: <span id="gravitySpeed"></span></p>
    <p>posY: <span id="posY"></span></p>
</div>

和updateGameArea函数中的这样一个块

...
myGamePiece.newPos();

// -- debug --
speedY.innerText = myGamePiece.speedY.toFixed(2);
gravitySpeed.innerText = myGamePiece.gravitySpeed.toFixed(2);
posY.innerText = myGamePiece.y.toFixed(2);
// -----------

myGamePiece.update();

在画布上跳跃

1 个答案: