javascript结合Canvas 实现简易的圆形时钟

之前学习了下html5中的canvas元素，为了练练手就实现了一个简易的时钟。时钟本身并不复杂，也没有使用图片进行美化，不过麻雀虽小五脏俱全，下面就与大家分享一下：

演示效果：

html代码：


<!DOCTYPE html>

<html>

<head>

    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

    <title>Clock</title>

    <style type="text/css">

    *{

        margin: 0;

        padding: 0;

    }

    .canvas{

        margin-left: 20px;

        margin-top: 20px;

        border: solid 1px;

    }

    </style>

</head>

<body onload= "main()">

<canvas class = "canvas" id="canvasId" width = '500px' height = '400px'></canvas>

<script type= "text/javascript" src = "Clock.js"></script>

</body>

</html>

JS代码:


var Canvas = {};

Canvas.cxt = document.getElementById('canvasId').getContext('2d');

Canvas.Point = function(x, y){

    this.x = x;

    this.y = y;

};

/*擦除canvas上的所有图形*/

Canvas.clearCxt = function(){

    var me = this;

    var canvas = me.cxt.canvas;

       me.cxt.clearRect(0,0, canvas.offsetWidth, canvas.offsetHeight);

};

/*时钟*/

Canvas.Clock = function(){

    var me = Canvas,

        c = me.cxt,

        radius = 150, /*半径*/

        scale = 20, /*刻度长度*/

        minangle = (1/30)*Math.PI, /*一分钟的弧度*/

        hourangle = (1/6)*Math.PI, /*一小时的弧度*/

        hourHandLength = radius/2, /*时针长度*/

        minHandLength = radius/3*2, /*分针长度*/

        secHandLength = radius/10*9, /*秒针长度*/

        center = new me.Point(c.canvas.width/2, c.canvas.height/2); /*圆心*/

    /*绘制圆心（表盘中心）*/

    function drawCenter(){

        c.save();

        c.translate(center.x, center.y); 

        c.fillStyle = 'black';

        c.beginPath();

        c.arc(0, 0, radius/20, 0, 2*Math.PI);

        c.closePath();

        c.fill();

        c.stroke();

        c.restore();

    };

    /*通过坐标变换绘制表盘*/

    function drawBackGround(){

        c.save();

        c.translate(center.x, center.y); /*平移变换*/

        /*绘制刻度*/

        function drawScale(){

           c.moveTo(radius - scale, 0);

           c.lineTo(radius, 0); 

        };

        c.beginPath();

        c.arc(0, 0, radius, 0, 2*Math.PI, true);

        c.closePath();

        for (var i = 1; i <= 12; i++) {

           drawScale();

           c.rotate(hourangle); /*旋转变换*/

        };

        /*绘制时间(3,6,9,12)*/

        c.font = " bold 30px impack"

        c.fillText("3", 110, 10);

        c.fillText("6", -7, 120);

        c.fillText("9", -120, 10);

        c.fillText("12", -16, -100);

        c.stroke();

        c.restore();

    };

    /*绘制时针(h: 当前时（24小时制）)*/

    this.drawHourHand = function(h){

        h = h === 0? 24: h;

        c.save();

        c.translate(center.x, center.y); 

        c.rotate(3/2*Math.PI);

        c.rotate(h*hourangle);

        c.beginPath();

        c.moveTo(0, 0);

        c.lineTo(hourHandLength, 0);

        c.stroke();

        c.restore();

    };

    /*绘制分针（m: 当前分）*/

    this.drawMinHand = function(m){

        m = m === 0? 60: m;

        c.save();

        c.translate(center.x, center.y); 

        c.rotate(3/2*Math.PI);

        c.rotate(m*minangle);

        c.beginPath();

        c.moveTo(0, 0);

        c.lineTo(minHandLength, 0);

        c.stroke();

        c.restore();

    };

    /*绘制秒针（s：当前秒）*/

    this.drawSecHand = function(s){

        s = s === 0? 60: s;

        c.save();

        c.translate(center.x, center.y); 

        c.rotate(3/2*Math.PI);

        c.rotate(s*minangle);

        c.beginPath();

        c.moveTo(0, 0);

        c.lineTo(secHandLength, 0);

        c.stroke();

        c.restore();

    };

    /*依据本机时间绘制时钟*/

    this.drawClock = function(){

        var me = this;

        function draw(){

           var date = new Date();

           Canvas.clearCxt();

           drawBackGround();

           drawCenter();

           me.drawHourHand(date.getHours() + date.getMinutes()/60);

           me.drawMinHand(date.getMinutes() + date.getSeconds()/60);

           me.drawSecHand(date.getSeconds());

        }

        draw();

        setInterval(draw, 1000);

    };  

};

 var main = function(){

    var clock = new Canvas.Clock();

    clock.drawClock();

};

代码中涉及到了一些简单的canvas元素API 大家度娘一下即可

以上就是本文的全部内容了，希望对大家学习canvas能够有所帮助。

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