HTML5，JavaScript和在画布上绘制多个矩形 [英] HTML5, JavaScript and drawing multiple rectangles in a canvas
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问题描述
为什么我的多个矩形不会在画布上绘制？
Why won't my multiple rectangles draw in the canvas?
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<script src="Scripts/jquery-1.9.1.min.js"></script>
</head>
<body>
<canvas id="myCanvas" width="500" height="500" style="border:1px solid red">
<p>Your browser doesn't support canvas.</p>
</canvas>
</body>
</html>
<script type ="text/javascript">
function Shape(x, y, w, h, fill) {
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.fill = fill;
}
// get canvas element.
var elem = document.getElementById('myCanvas');
// check if context exist
if (elem.getContext) {
var myRect = [];
myRect.push(new Shape(10, 0, 25, 25, "#333"))
myRect.push(new Shape(0, 40, 39, 25, "#333"))
myRect.push(new Shape(0, 80, 100, 25, "#333"))
context = elem.getContext('2d');
for (i in myRect) {
//console.log(x);
context.fillRect(i.x, i.y, i.w, i.h)
}
//// x, y, width, height
//context.fillRect(0, 0, 50, 50);
//// x, y, width, height
//context.fillRect(75, 0, 50, 50);
}
</script>
感谢您的帮助。
推荐答案
好的，所以你几乎在那里。
当你对矩形数组进行迭代时，你将遍历数组键而不是对象本身（参见）。
加上，如@ jimjimmy1995指出，你需要使用 .fillStyle 设置填充。 fillRect 没有填充参数。
Ok, so you were almost there.
When you iterate round your array of rectangles, you are iterating over the array key not the objects themselves (see How to Loop through JavaScript object literal with objects as members?).
Plus, as @jimjimmy1995 pointed out, you need to set the fill using .fillStyle as .fillRect does not have a fill parameter.
此代码将起作用：
function Shape(x, y, w, h, fill) {
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.fill = fill;
}
// get canvas element.
var elem = document.getElementById('myCanvas');
// check if context exist
if (elem.getContext) {
var myRect = [];
myRect.push(new Shape(10, 0, 25, 25, "#333"));
myRect.push(new Shape(0, 40, 39, 25, "#333"));
myRect.push(new Shape(0, 80, 100, 25, "#333"));
context = elem.getContext('2d');
for (var i in myRect) {
oRec = myRect[i];
context.fillStyle = oRec.fill;
context.fillRect(oRec.x, oRec.y, oRec.w, oRec.h);
}
}
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