清除按钮不适用于我的 javascript 和 hmtl5 画布
[英]Clear button not working with my javascript and hmtl5 canvas
问题描述
I'am very new at this and I'm trying to create a signature drawing program in html, canvas and javascript.
我对此很陌生，我正在尝试用 html、canvas 和 javascript 创建一个签名绘图程序。
Im trying to get the clear button working with this function;我试图让清除按钮使用此功能；
function clearCanvas() {
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
But it does not seem to work.但它似乎不起作用。 I don't really know where in the js script to put the function for it to be executed in the html code.我真的不知道在 js 脚本中的何处放置要在 html 代码中执行的函数。
this is the html code:这是 html 代码：
<!DOCTYPE html>
<html lang="sv">
<head>
<meta charset="utf-8">
<script type="text/javascript" src="uppgift-6.js"></script>
<title>Uppgift6</title>
<style type="text/css">
#canvas { position: relative; }
#bildruta { border: 2px solid #000; }
body {font-family: Calibri}
h2 {font-size: 150%; color: BLACK; background-color: BEIGE; padding: 20px; margin: 5px auto; text-align: center;}
</style>
</head>
<body>
<h2>Signatur</h2>
<div id="canvas">
<canvas id="bildruta" width="600" height="400"></canvas>
</div>
<button type="button" onclick="clearCanvas()"> Clear signature </button>
</body>
</html>
Grateful for all help that i can get!感谢我能得到的所有帮助！
2 个解决方案
解决方案1
1 2016-04-25 09:48:42
Your ID is not correct.您的 ID 不正确。 Change your id or change the JS line like this:更改您的 id 或更改 JS 行，如下所示：
function clearCanvas() {
var canvas = document.getElementById('bildruta'); // that's the correct ID
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
}
And it works.它有效。
解决方案2
1 2016-04-25 09:50:25
var canvas = document.getElementById('canvas') points to this div <div id="canvas"> not to your canvas. var canvas = document.getElementById('canvas')指向这个 div <div id="canvas">而不是你的画布。 It should be document.getElementById('bildruta')它应该是document.getElementById('bildruta')
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