我有两个故意重叠的 Canvas ，以绘制落在另一个 Canvas 上的球。我想将第三个 Canvas 放在页面上那两个重叠的 Canvas 下方，没有任何重叠。当容纳重叠 Canvas 的 div 元素具有相对位置时，它不会阻止其他元素重叠它。据我了解，该 div 必须相对定位，以便其中的 Canvas 可以绝对定位并重叠。
这是我的 HTML:
<div id="box" style="position: relative;"></div>
<div id="countdiv"></div>
这是 JavaScript:
boxCanvas = document.createElement("canvas");
// the margins on the page are 3%
boxCanvas.width = window.innerWidth - (window.innerWidth * .06);
boxCanvas.height = document.getElementById("height").value;
boxCanvas.style = "border: 1px solid #808080; position: absolute; left: 0; top: 0; z-index: 0";
document.getElementById("box").appendChild(boxCanvas);
// second canvas for drawing balls falling
ballCanvas = document.createElement("canvas");
ballCanvas.width = boxCanvas.width;
ballCanvas.height = boxCanvas.height;
ballCanvas.style = "border: 1px solid #808080; position: absolute; left: 0; top: 0; z-index: 1";
document.getElementById("box").appendChild(ballCanvas);
这是第三个 Canvas 的 JavaScript:
countCanvas = document.createElement("canvas");
countCanvas.width = window.innerWidth - (window.innerWidth * .06);
countCanvas.height = 100;
countCanvas.style = "border: 1px solid #808080;";
document.getElementById("box").appendChild(countCanvas);
countctx = countCanvas.getContext("2d");
ballCanvas.height = boxCanvas.height;
ballCanvas.style = "border: 1px solid #808080; position: absolute; left: 0; top: 0; z-index: 1";
document.getElementById("countdiv").appendChild(ballCanvas);
问题可见here当您单击 drawbox() 然后“显示点击数”时。谢谢您的帮助!让我知道是否可以提供更多信息。
最佳答案
我必须承认我不太确定你在问什么。
我想你想在顶部有 2 个重叠的 Canvas ，然后在底部有一个单独的 Canvas 。
并且您想使用 javascript 而不是 CSS 进行样式设置。
这是代码和 fiddle :http://jsfiddle.net/m1erickson/hgHBw/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
#box{
border:1px solid blue;
}
.subcanvs{
border: 1px solid green;
}
#countCanvas{
border: 1px solid gold;
}
</style>
<script>
$(function(){
var w=300;
var h=200;
var boxDiv=document.getElementById("box");
boxDiv.style.width=w+"px";
boxDiv.style.height=h+"px";
boxDiv.style.position="relative";
var box=document.getElementById("boxCanvas");
var boxCtx=box.getContext("2d");
box.width=w;
box.height=h;
box.style.position="absolute";
box.style.left=0;
box.style.top=0;
var ball=document.getElementById("ballCanvas");
var ballCtx=ball.getContext("2d");
ball.width=w;
ball.height=h;
ball.style.position="absolute";
ball.style.left=0;
ball.style.top=0;
var counter=document.getElementById("countCanvas");
var countCtx=counter.getContext("2d");
counter.width=w;
counter.height=100;
test(boxCtx,20,30,"red");
test(ballCtx,100,30,"green");
test(countCtx,30,30,"blue");
function test(ctx,x,y,color){
ctx.beginPath();
ctx.fillStyle=color;
ctx.rect(x,y,50,50);
ctx.fill();
}
}); // end $(function(){});
</script>
</head>
<body>
<div id="box">
<canvas id="boxCanvas" class="subcanvs"></canvas>
<canvas id="ballCanvas" class="subcanvs"></canvas>
</div>
<canvas id="countCanvas"></canvas>
</body>
</html>
需要注意的一点:
// this sets the canvas drawing area to 100px wide
myCanvas.width=100;
// this styles the canvas element to be 100px wide on the page
// if this isn't == myCanvas.width then the image will be horizontally distorted
myCanvas.style.width="100px";
关于javascript - 将 Canvas 定位在重叠 Canvas 下方，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16876179/