javascript結合Canvas 實現簡易的圓形時鐘

2019-11-20 12:59:22

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之前學習了下html5中的canvas元素，為了練練手就實現了一個簡易的時鐘。時鐘本身并不復雜，也沒有使用圖片進行美化，不過麻雀雖小五臟俱全，下面就與大家分享一下：

演示效果：

html代碼：

<!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代碼:

復制代碼代碼如下:

var Canvas = {};
Canvas.cxt = document.getElementById('canvasId').getContext('2d');
Canvas.Point = function(x, y){
    this.x = x;
    this.y = y;
};
/*擦除canvas上的所有圖形*/
Canvas.clearCxt = function(){
    var me = this;
    var canvas = me.cxt.canvas;
       me.cxt.clearRect(0,0, canvas.offsetWidth, canvas.offsetHeight);
};
/*時鐘*/
Canvas.Clock = function(){
    var me = Canvas,
        c = me.cxt,
        radius = 150, /*半徑*/
        scale = 20, /*刻度長度*/
        minangle = (1/30)*Math.PI, /*一分鐘的弧度*/
        hourangle = (1/6)*Math.PI, /*一小時的弧度*/
        hourHandLength = radius/2, /*時針長度*/
        minHandLength = radius/3*2, /*分針長度*/
        secHandLength = radius/10*9, /*秒針長度*/
        center = new me.Point(c.canvas.width/2, c.canvas.height/2); /*圓心*/
    /*繪制圓心（表盤中心）*/
    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();
    };
    /*通過坐標變換繪制表盤*/
    function drawBackGround(){
        c.save();
        c.translate(center.x, center.y); /*平移變換*/
        /*繪制刻度*/
        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); /*旋轉變換*/
        };
        /*繪制時間(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();
    };
    /*繪制時針(h: 當前時（24小時制）)*/
    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();
    };
    /*繪制分針（m: 當前分）*/
    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();
    };
    /*繪制秒針（s：當前秒）*/
    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();
    };
    /*依據本機時間繪制時鐘*/
    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();
};