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對於此項目,我們正在使用畫布。我需要創建一些按鈕,當你點擊按鈕時,應該調用相應的函數。這些函數會在畫布中繪製一些東西。但是,我的代碼不起作用。按鈕和畫布本身出現,但是當您單擊按鈕時沒有繪製任何東西。有沒有錯誤?如何使用按鈕調用在畫布中繪製的函數
<script>
function drawCircle(){
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(95,50,40,0,2*Math.PI);
ctx.stroke();
}
function drawLine(){
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(0,0);
ctx.lineTo(200,100);
ctx.stroke();
}
function drawRectangle(){
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.fillStyle = "#FF0000";
ctx.fillRect(0,0,150,75);
}
function drawImage(){
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("scream");
ctx.drawImage(img,10,10);
}
function drawText(){
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.fillText("Hello World",10,50);
}
</script>
</head>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;">
</canvas>
<input type="button" onclick="drawCircle();" value="Draw Circle">
<input type="button" onclick="drawLine();" value="Draw Line">
<input type="button" onclick="drawRectangle();" value="Draw Rectangle">
<input type="button" onclick="drawImage();" value="Draw Line">
<input type="button" onclick="drawText();" value="Text">
<input type="button" onclick="drawGradient();" value="Gradient">
<input type="button" onclick="scale();" value="Scale">
</body>
</html>
它似乎爲我工作得很好(至少在Chrome和IE中)。你如何運行它? –