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详解通过Canvas + JS 实现简易的时钟

2015-03-27  来源:博客园  我有话说  收藏本文  阅读  次

 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:

实现效果:

通过Canvas + JS 实现简易的时钟

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Google一下即可,祝大家学习愉快:-D

原文出自:http://www.cnblogs.com/liubingblog/archive/2015/03/10/4325063.html

(责编:tianji)
关键词: 简易时钟

声明:原文出自//article.nxpop.com/js/2015-03-27/267.html ,文章观点仅代表原作者,转载请注明出处。

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