参考视频资料:Canvas 绘制时钟
最近复习到 Canvas, 先准备来段有趣的代码，用 Canvas 绘制出一个动态的时钟。然后后续再对 Canvas 进行进一步学习。以下代码均来自以上链接所属的视频教程。【侵删】
完整代码：
<!DOCTYPE html>
<html lang=”en”>
<head>
<meta charset=”UTF-8″>
<meta name=”viewport” content=”width=device-width, initial-scale=1.0″>
<meta http-equiv=”X-UA-Compatible” content=”ie=edge”>
<title>Document</title>
<style type=”text/css”>
div {
text-align: center;
margin-top: 250px;
}
</style>
</head>
<body>
<div>
<canvas id=”clock” height=”200px” width=”200px”> 你的浏览器不支持 canvas</canvas>
</div>
<script>
var dom = document.getElementById(‘clock’);
var ctx = dom.getContext(‘2d’);
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
// 绘制表盘
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();
var hourNumbers = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2];
ctx.font = ’18px Arial’;
ctx.textAlign = ‘center’;
ctx.textBaseline = ‘middle’;
// 小时数字
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);
// console.log(x)
})
// 绘制分刻度
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();
}
}
// 绘制时针
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();
}
// 绘制分针
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();
}
// 绘制秒针
function drawSecond(second) {
ctx.save();
ctx.beginPath();
ctx.fillStyle = ‘red’
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();
}
// 绘制指针的端点
function drawDot() {
ctx.beginPath();
ctx.fillStyle = ‘white’;
ctx.arc(0, 0, 3, 0, 2 * Math.PI, false);
ctx.fill();
}
// 动起来
function draw() {
// 清除之前所绘制的
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>