为什么按视频上写的最后出不来圆呢，求大神指教
代码什么的都对
2 回答
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas clock</title>
<style type="text/css">
div{text-align: center; margin-top: 230px;}
#clock{border: 1px solid #fff;}
</style>
</head>
<body>
<div>
<canvas id="clock" height="200px" width="200px"></canvas>
</div>
<script type="text/javascript">
var dom=document.getElementById('clock');
var ctx = dom.getContext('2d');
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
//圆形
function drawBackground(){
ctx.save();
ctx.translate(r, r);
ctx.beginPath();
ctx.lineWidth = 10;
ctx.arc(0, 0, r - 5, 0, 2*Math.PI, false);
ctx.stroke();
drawBackground();
</script>
</body>
</html>
为什么写成上面的代码不能显示
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas clock</title>
<style type="text/css">
div{text-align: center; margin-top: 230px;}
#clock{border: 1px solid #fff;}
</style>
</head>
<body>
<div>
<canvas id="clock" height="200px" width="200px"></canvas>
</div>
<script type="text/javascript">
var dom=document.getElementById('clock');
var ctx = dom.getContext('2d');
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
//圆形
function drawBackground(){
ctx.save();
ctx.translate(r, r);
ctx.beginPath();
ctx.lineWidth = 10;
ctx.arc(0, 0, r - 5, 0, 2*Math.PI, false);
ctx.stroke();
//数字
var hourNumbers=[3,4,5,6,7,8,9,10,11,12,1,2];
ctx.font = '18px Arial';
ctx.textAlign = 'center';
ctx.textBaseline = 'middle';
hourNumbers.forEach(function (number,i){
var rad = 2 * Math.PI / 12 * i;
var x = Math.cos(rad) * (r - 30);
var y = Math.sin(rad) * (r - 30);
ctx.fillText(number,x,y);
});
//小点
for(var i = 0; i < 60; i++){
var rad = 2 * Math.PI / 60 * i;
var x = Math.cos(rad) * (r - 18);
var y = Math.sin(rad) * (r - 18);
ctx.beginPath();
if (i % 5 == 0) {
ctx.fillStyle='#000';
ctx.arc(x, y, 2, 0, 2 * Math.PI, false);
}else{
ctx.fillStyle='#ccc';
ctx.arc(x, y, 2, 0, 2 * Math.PI, false);
}
ctx.fill();
}
}
//时针
function drawHour(hour,minute){
ctx.save();
ctx.beginPath();
var rad = 2 * Math.PI / 12 * hour;
var mrad = 2 * Math.PI / 12 / 60 * minute;
ctx.rotate(rad + mrad);
ctx.lineWidth=6;
ctx.lineCap='round';
ctx.moveTo(0,10);
ctx.lineTo(0,-r / 2);
ctx.stroke();
ctx.restore();
}
//分针
function drawMinute(minute){
ctx.save();
ctx.beginPath();
var rad = 2 * Math.PI / 60 * minute;
ctx.rotate(rad);
ctx.lineWidth=3;
ctx.lineCap='round';
ctx.moveTo(0,10);
ctx.lineTo(0,-r + 30);
ctx.stroke();
ctx.restore();
}
//秒针
function drawSecond(second){
ctx.save();
ctx.beginPath();
ctx.fillStyle='#c14543';
var rad = 2 * Math.PI / 60 * second;
ctx.rotate(rad);
ctx.moveTo(-2,20);
ctx.lineTo(2, 20);
ctx.lineTo(1, -r + 18);
ctx.lineTo(-1, -r + 18);
ctx.fill();
ctx.restore();
}
//圆点
function drawDot(){
ctx.beginPath();
ctx.fillStyle='#fff';
ctx.arc(0,0,3,0,2*Math.PI, false);
ctx.fill();
}
function draw(){
ctx.clearRect(0,0,width,height);
var now = new Date();
var hour = now.getHours();
var minute = now.getMinutes();
var second = now.getSeconds();
drawBackground();
drawHour(hour, minute);
drawMinute(minute);
drawSecond(second);
drawDot();
ctx.restore();
}
draw();
setInterval(draw,1000);
</script>
</body>
</html>
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