0
那么,看看这个代码,主要是函数中的drawPaddle
函数和var paddleY
。在画布上绘制带变量的rect() - 仅适用于数字?
<!DOCTYPE html>
<html>
<head>
\t <title>GAME</title>
\t <meta charset="utf-8"/>
\t <style type="text/css">
\t \t canvas {
\t \t \t background-color: gray;
\t \t }
\t </style>
</head>
<body>
\t <canvas width="500" height="500" id="myCanvas"></canvas>
\t
\t <script type="text/javascript">
\t \t var canvas = document.getElementById('myCanvas'); \t
\t \t var ctx = canvas.getContext('2d');
\t \t var ballX = canvas.width/2;
\t \t var ballY = canvas.height - 80;
\t \t var ballR = 10;
\t \t var ballMX = 2;
\t \t var ballMY = -2;
\t \t var paddleX = (canvas.width/2) - (130/2);
\t \t var paddleY = canvas.height - paddleH;
\t \t var paddleW = 130;
\t \t var paddleH = 15;
\t \t function drawPaddle() {
\t \t \t ctx.beginPath();
\t \t \t ctx.fillStyle = "green";
\t \t \t ctx.rect(paddleX, paddleY, paddleW, paddleH);
\t \t \t ctx.fill();
\t \t \t ctx.closePath();
\t \t }
\t \t drawPaddle();
\t </script>
</body>
</html>
在var paddleY
我得到canvas.height - paddleH
,这个代码不画桨,但是当我在var paddleY
canvas.height - 15
改变,它正在它为什么呢?