这一个demo没有什么特别的知识点,总结起来就有些如下:
1.如何获取一个时间对象
var now = new Date();
2.获取当前时间的时分秒
var sec = now.getSeconds(); var min = now.getMinutes(); var hour = now.getHours();
3.要将24小时制转化为12小时制
hour = hour+min/60;
hour = hour>12?hour-12:hour;
4.画表盘
cxt.lineWidth = 10; cxt.strokeStyle = '#ABCDEF'; cxt.beginPath(); cxt.arc(250,250,200,0,360,false); cxt.closePath(); cxt.stroke();
5.画刻度
//刻度 //时刻度 for(var i=0; i<12; i++){ cxt.save(); cxt.lineWidth = 7; cxt.strokeStyle = '#000'; //设置0,0点 cxt.translate(250,250); //设置旋转角度 cxt.rotate(i*30*Math.PI/180);//角度 = *MAth.PI/180=弧度 cxt.beginPath(); cxt.moveTo(0,-170); cxt.lineTo(0,-190); cxt.closePath(); cxt.stroke(); cxt.restore(); } //分刻度 for(var i=0; i<60; i++){ cxt.save(); cxt.lineWidth = 5; cxt.strokeStyle = '#000'; cxt.translate(250,250); //设置旋转角度 cxt.rotate(i*6*Math.PI/180); cxt.beginPath(); cxt.moveTo(0,-180); cxt.lineTo(0,-190); cxt.stroke(); cxt.closePath(); cxt.restore(); }
6.画指针
//时针 cxt.save(); //设置时针风格 cxt.lineWidth = 7; cxt.strokeStyle = '#000' cxt.translate(250,250); cxt.rotate(hour*30*Math.PI/180); cxt.beginPath(); cxt.moveTo(0,-130); cxt.lineTo(0,10); cxt.stroke(); cxt.closePath(); cxt.restore(); //分针 cxt.save(); cxt.lineWidth = 5; cxt.strokeStyle = '#000' cxt.translate(250,250); cxt.rotate(min*6*Math.PI/180); cxt.beginPath(); cxt.moveTo(0,-150); cxt.lineTo(0,15); cxt.stroke(); cxt.closePath(); cxt.restore(); //秒针 cxt.save(); cxt.strokeStyle = 'red'; cxt.lineWidth = 3; cxt.translate(250,250); cxt.rotate(sec*6*Math.PI/180); cxt.beginPath(); cxt.moveTo(0,-170); cxt.lineTo(0,20); cxt.stroke(); cxt.closePath(); //画出时针,分针,秒针的交叉点 cxt.beginPath(); cxt.arc(0,0,5,0,360,false); cxt.closePath(); cxt.fillStyle = "gray"; cxt.fill(); cxt.strokeStyle = 'red'; cxt.stroke(); //设置秒针的小圆点 cxt.beginPath(); cxt.arc(0,-135,5,0,360,false); cxt.closePath(); cxt.fillStyle = "gray"; cxt.fill(); cxt.strokeStyle = 'red'; cxt.stroke(); cxt.restore(); }
7.让指针动起来
//使用setInterval(代码,毫秒时间) 让时钟动起来 setInterval(drawClock,1000);
8.防止刷新的时候页面出现空白,应该
setInterval(drawClock,1000);之前加上 drawClock();
代码如下:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>canvas时钟</title>
</head>
<body>
<canvas id="canvas" width="500" height="500">您的浏览器不支持canvas</canvas>
<script>
var clock = document.getElementById('canvas');
var cxt = clock.getContext('2d');
function drawClock() {
cxt.clearRect(0,0,500,500);
//获取一个时间对象
var now = new Date();
var sec = now.getSeconds();
var min = now.getMinutes();
var hour = now.getHours();
//小时必须获取浮点类型
hour = hour+min/60;
//这里存在一个时间格式,要将24小时制转化为12小时制
hour = hour>12?hour-12:hour;
//表盘(蓝色)
cxt.lineWidth = 10;
cxt.strokeStyle = '#ABCDEF';
cxt.beginPath();
cxt.arc(250,250,200,0,360,false);
cxt.closePath();
cxt.stroke();
//刻度
//时刻度
for(var i=0; i<12; i++){
cxt.save();
cxt.lineWidth = 7;
cxt.strokeStyle = '#000';
//设置0,0点
cxt.translate(250,250);
//设置旋转角度
cxt.rotate(i*30*Math.PI/180);//角度 = *MAth.PI/180=弧度
cxt.beginPath();
cxt.moveTo(0,-170);
cxt.lineTo(0,-190);
cxt.closePath();
cxt.stroke();
cxt.restore();
}
//分刻度
for(var i=0; i<60; i++){
cxt.save();
cxt.lineWidth = 5;
cxt.strokeStyle = '#000';
cxt.translate(250,250);
//设置旋转角度
cxt.rotate(i*6*Math.PI/180);
cxt.beginPath();
cxt.moveTo(0,-180);
cxt.lineTo(0,-190);
cxt.stroke();
cxt.closePath();
cxt.restore();
}
//时针
cxt.save();
//设置时针风格
cxt.lineWidth = 7;
cxt.strokeStyle = '#000'
cxt.translate(250,250);
cxt.rotate(hour*30*Math.PI/180);
cxt.beginPath();
cxt.moveTo(0,-130);
cxt.lineTo(0,10);
cxt.stroke();
cxt.closePath();
cxt.restore();
//分针
cxt.save();
cxt.lineWidth = 5;
cxt.strokeStyle = '#000'
cxt.translate(250,250);
cxt.rotate(min*6*Math.PI/180);
cxt.beginPath();
cxt.moveTo(0,-150);
cxt.lineTo(0,15);
cxt.stroke();
cxt.closePath();
cxt.restore();
//秒针
cxt.save();
cxt.strokeStyle = 'red';
cxt.lineWidth = 3;
cxt.translate(250,250);
cxt.rotate(sec*6*Math.PI/180);
cxt.beginPath();
cxt.moveTo(0,-170);
cxt.lineTo(0,20);
cxt.stroke();
cxt.closePath();
//画出时针,分针,秒针的交叉点
cxt.beginPath();
cxt.arc(0,0,5,0,360,false);
cxt.closePath();
cxt.fillStyle = "gray";
cxt.fill();
cxt.strokeStyle = 'red';
cxt.stroke();
//设置秒针的小圆点
cxt.beginPath();
cxt.arc(0,-135,5,0,360,false);
cxt.closePath();
cxt.fillStyle = "gray";
cxt.fill();
cxt.strokeStyle = 'red';
cxt.stroke();
cxt.restore();
}
drawClock();
//使用setInterval(代码,毫秒时间) 让时钟动起来
setInterval(drawClock,1000);
</script>
</body>
</html>