canvas ：原生javascript编写动态时钟

时间 2019-12-05

标签 canvas 原生 javascript 编写动态时钟栏目 JavaScript 繁體版

原文原文链接

canvas ：原生javascript编写动态时钟

此时针是以画布的中心为圆心；javascript

g.translate(width/2,width/2);css

此函数是将画布的原点移到(width/2,width/2)html

绘制表盘

function jiang(){
                r = width/2
                g.clearRect(0, 0, 600, 600);
                
                g.save();
                g.translate(r, r);
                g.rotate(-Math.PI / 2);

              //分钟刻度线

                for(var i = 0; i < 60; i++) {//画60个刻度线
                    g.beginPath();
                    g.strokeStyle ="white";
                    g.lineWidth = 4;
                    g.moveTo(250, 0);
                    g.lineTo(240, 0);
                    g.stroke();
                    g.rotate(Math.PI / 30); //每一个6deg画一个时钟刻度线
                    g.closePath();
                }

              //时钟刻度线
                for(var i = 0; i < 12; i++) {//画12个刻度线
                    g.beginPath();
                    g.strokeStyle ="white";
                    g.lineWidth = 8;
                    g.moveTo(250, 0);
                    g.lineTo(230, 0);
                    g.stroke();
                    g.rotate(Math.PI / 6); //每一个30deg画一个时钟刻度
                    g.closePath();
                }
            }

时针

save和restore必不可少，在这两个函数之间，改变位置不会影响到其余函数，在此段代码中特指rotate，若是没有rotate，能够不用save和restorejava

必定要加beginPath，省得被其余函数影响canvas

时针和分针秒针不同，一个30°，还有分针的移动会影响时针的位置函数

时针运动的原理是画好一条线，而后旋转那条线post

            function drawHour(hour,minu){
                g.save();
                g.beginPath();
                g.lineWidth = 9; var rad = Math.PI*2/12*hour; var radMinu = Math.PI*2/12/60*minu; g.rotate(rad + radMinu) g.moveTo(-10,0); g.lineTo(r/2,0); g.strokeStyle = "white"; g.stroke(); g.restore(); }

分针

            function drawMinu(minu){ g.save(); g.beginPath(); g.lineWidth = 6; var radMinu = Math.PI*2/60*minu;  g.rotate(radMinu) g.moveTo(-16,0); g.lineTo(r-100,0); g.strokeStyle = "white"; g.stroke(); g.restore(); }

秒针

　　　　　　　function drawSeco(seco){
                g.save();
                g.beginPath();
                g.lineWidth = 3; var radSeco = Math.PI*2/60*seco;  g.rotate(radSeco) g.moveTo(-25,0); g.lineTo(r-80,0); g.strokeStyle = "#ff0032"; g.stroke(); g.restore(); }

数字表

        function drawNumClock(){
            var data = new Date(); var sec = data.getSeconds(); var min = data.getMinutes(); var hour = data.getHours(); g.fillStyle = "white"; g.font = "20px '楷体'"; g.beginPath(); g.rotate(Math.PI/2) g.fillText(hour,60,0); g.fillText(":",80,0); g.fillText(min,90,0); g.font = "20px '楷体'"; g.fillText(sec,120,0); }

下面附上总体代码：

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>时钟</title>
        <style type="text/css">
            .kuang{
                width: 600px; 
                height: 600px;
                margin: auto;
                padding: 5;
            }
        </style>
    </head>
    <body>
        <div class="kuang">
        <canvas id="zhong" width="600" height="600"></canvas>
        </div>
        <script type="text/javascript">
            var canvas =document.querySelector("canvas");
            canvas.style.background ="paleturquoise";
            var g = canvas.getContext("2d");  
            var width = canvas.width;
            var height = canvas.height;

          

                   //绘制转盘时钟

            function jiang(){
                r = width/2
                g.clearRect(0, 0, 600, 600);
                
                g.save();
                g.translate(r, r);
                g.rotate(-Math.PI / 2);

              //分钟刻度线

                for(var i = 0; i < 60; i++) {//画60个刻度线
                    g.beginPath();
                    g.strokeStyle ="white";
                    g.lineWidth = 4;
                    g.moveTo(250, 0);
                    g.lineTo(240, 0);
                    g.stroke();
                    g.rotate(Math.PI / 30); //每一个6deg画一个时钟刻度线
                    g.closePath();
                }

              //时钟刻度线
                for(var i = 0; i < 12; i++) {//画12个刻度线
                    g.beginPath();
                    g.strokeStyle ="white";
                    g.lineWidth = 8;
                    g.moveTo(250, 0);
                    g.lineTo(230, 0);
                    g.stroke();
                    g.rotate(Math.PI / 6); //每一个30deg画一个时钟刻度
                    g.closePath();
                }
            }

                /*画时针*/
            function drawHour(hour,minu){
                g.save();
                g.beginPath();
                g.lineWidth = 9;
                var rad = Math.PI*2/12*hour;
                var radMinu = Math.PI*2/12/60*minu;
                g.rotate(rad + radMinu)
                g.moveTo(-10,0);
                g.lineTo(r/2,0);
                g.strokeStyle = "white";
                g.stroke();
                g.restore();
            }
                /*画分针*/
            function drawMinu(minu){
                g.save();
                g.beginPath();
                g.lineWidth = 6;
                var radMinu = Math.PI*2/60*minu;
                g.rotate(radMinu)
                g.moveTo(-16,0);
                g.lineTo(r-100,0);
                g.strokeStyle = "white";
                g.stroke();
                g.restore();
            }
                /*画秒针*/
            function drawSeco(seco){
                g.save();
                g.beginPath();
                g.lineWidth = 3;
                var radSeco = Math.PI*2/60*seco;
                g.rotate(radSeco)
                g.moveTo(-25,0);
                g.lineTo(r-80,0);
                g.strokeStyle = "#ff0032";
                g.stroke();
                g.restore();
            }
            /*数字表*/
        function drawNumClock(){
            var data = new Date();

            var sec = data.getSeconds();
            var min = data.getMinutes();
            var hour = data.getHours();

            g.fillStyle = "white";
            g.font = "20px '楷体'";
            g.beginPath();
            g.rotate(Math.PI/2)        
            g.fillText(hour,60,0);
            g.fillText(":",80,0);
            g.fillText(min,90,0);
            g.font = "20px '楷体'";
            g.fillText(sec,120,0);

        }

        function draw(){
            
            var data = new Date();
            var sec = data.getSeconds();
            var min = data.getMinutes();
            var hour = data.getHours();
            jiang();
            drawHour(hour,min);
            drawMinu(min);
            drawSeco(sec);
            drawNumClock()
            g.restore();
            
        }
            
        setInterval(draw,10)

        </script>
    
    </body>
</html>