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：

代码如下:

<!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:

代码如下:

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。