html5 loading 效果来了

yukaizhao · 发表于 2013-1-29 08:53:16

Html5在移动设备上表现抢眼，几乎所有稍微高端一点的设备（乔帮主的iPad，iPhone和Andriod的平板手机等）的浏览器都支持Html5。而且据我个人的测试这些支持html5的设备对canvas标签的支持是相当的好。

大家都知道web2.0以来大量的使用ajax，loading的小图标也有很多很多种，甚至还有专门提供loading图片的网站。所以我就想能不能让html5解决一下这个以前用gif文件解决的问题。没想到非常的简单，只用了不到一小时的时间就搞定了两个，而且这样做出来的loading图标是可定制的，既可以定制颜色，也可以定制大小等属性。

看看效果吧：
http://f200-8.bbs.hexun.com/e/111219/loading.htm
http://f200-8.bbs.hexun.com/e/111219/loading2.htm

第一个带着小尾巴转动的loading图标画图的思路是，首先画一个圆，然后在圆的边上按顺序画大小逐渐减小的小圆点，在每次刷新画布时改变这一系列的小圆点在大圆边上的位置。
<!doctype html><html> <head> <meta http-equiv="content-type" content="GBK"/> <title>loading</title> <script type="text/javascript"> /* html5 loading 控件作者：玉开博客：http://www.cnblogs.com/yukaizhao/ 发布或使用此控件，请保留作者声明 */ function loading(canvas,options){ this.canvas = canvas; if(options){ this.radius = options.radius||12; this.circleLineWidth = options.circleLineWidth||4; this.circleColor = options.circleColor||'lightgray'; this.dotColor = options.dotColor||'gray'; }else{ this.radius = 12; this.circelLineWidth = 4; this.circleColor = 'lightgray'; this.dotColor = 'gray'; } } loading.prototype = { show:function (){ var canvas = this.canvas; if(!canvas.getContext)return; if(canvas.__loading)return; canvas.__loading = this; var ctx = canvas.getContext('2d'); var radius = this.radius; var rotators = [{angle:0,radius:1.5},{angle:3/radius,radius:2},{angle:7/radius,radius:2.5},{angle:12/radius,radius:3}]; var me = this; canvas.loadingInterval = setInterval(function(){ ctx.clearRect(0,0,canvas.width,canvas.height); var lineWidth = me.circleLineWidth; var center = {x:canvas.width/2 - radius,y:canvas.height/2-radius}; ctx.beginPath(); ctx.lineWidth = lineWidth; ctx.strokeStyle = me.circleColor; ctx.arc(center.x,center.y,radius,0,Math.PI*2); ctx.closePath(); ctx.stroke(); for(var i=0;i<rotators.length;i++){ var rotatorAngle = rotators[i].currentAngle||rotators[i].angle; //在圆圈上面画小圆 var rotatorCenter = {x:center.x-(radius)*Math.cos(rotatorAngle) ,y:center.y-(radius)*Math.sin(rotatorAngle)}; var rotatorRadius = rotators[i].radius; ctx.beginPath(); ctx.fillStyle = me.dotColor; ctx.arc(rotatorCenter.x,rotatorCenter.y,rotatorRadius,0,Math.PI*2); ctx.closePath(); ctx.fill(); rotators[i].currentAngle = rotatorAngle+4/radius; } },50); }, hide:function(){ var canvas = this.canvas; canvas.__loading = false; if(canvas.loadingInterval){ window.clearInterval(canvas.loadingInterval); } var ctx = canvas.getContext('2d'); if(ctx)ctx.clearRect(0,0,canvas.width,canvas.height); } }; </script> </head> <body> <canvas id="canvas" width="300" height="100" style="border:1px solid #69c"></canvas> <p> <input type="button" value="HideLoading"/> <input type="button" value="showLoading"/> </p> <script> var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3}); loadingObj.show(); </script> </body></html>
第二个较为简单，在一个圆环上有一个相同圆心相同半径的圆弧在不停的转动。画图的步骤是首先画一个圆环，然后画一个不同颜色相同圆心半径的圆弧，在每次刷新画布时改变圆弧的起始角度。
<!doctype html><html><head> <meta http-equiv="content-type" content="text/html;charset=gbk"/> <title>loading</title> <script> /* html5 loading 控件作者：玉开博客：http://www.cnblogs.com/yukaizhao/ 发布或使用此控件，请保留作者声明 */ function loading(canvas,options){ this.canvas = canvas; if(options){ this.radius = options.radius||12; this.circleLineWidth = options.circleLineWidth||4; this.circleColor = options.circleColor||'lightgray'; this.moveArcColor = options.moveArcColor||'gray'; }else{ this.radius = 12; this.circelLineWidth = 4; this.circleColor = 'lightgray'; this.moveArcColor = 'gray'; } } loading.prototype = { show:function (){ var canvas = this.canvas; if(!canvas.getContext)return; if(canvas.__loading)return; canvas.__loading = this; var ctx = canvas.getContext('2d'); var radius = this.radius; var me = this; var rotatorAngle = Math.PI*1.5; var step = Math.PI/6; canvas.loadingInterval = setInterval(function(){ ctx.clearRect(0,0,canvas.width,canvas.height); var lineWidth = me.circleLineWidth; var center = {x:canvas.width/2 - radius,y:canvas.height/2-radius}; ctx.beginPath(); ctx.lineWidth = lineWidth; ctx.strokeStyle = me.circleColor; ctx.arc(center.x,center.y,radius,0,Math.PI*2); ctx.closePath(); ctx.stroke(); //在圆圈上面画小圆 ctx.beginPath(); ctx.strokeStyle = me.moveArcColor; ctx.arc(center.x,center.y,radius,rotatorAngle,rotatorAngle+Math.PI*.45); ctx.stroke(); rotatorAngle+=step; },50); }, hide:function(){ var canvas = this.canvas; canvas.__loading = false; if(canvas.loadingInterval){ window.clearInterval(canvas.loadingInterval); } var ctx = canvas.getContext('2d'); if(ctx)ctx.clearRect(0,0,canvas.width,canvas.height); } }; </script> </head> <body> <canvas id="canvas" width="300" height="100" style="border:1px solid #69c">您的浏览器不支持html5哟</canvas> <p> <input type="button" value="HideLoading"/> <input type="button" value="showLoading"/> </p> <script> var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3}); loadingObj.show(); </script> </body></html>

目前从移动设备对Html5的支持来看，html5大有可为。
天下大势，合久必分，分久必和。PC开发时web应用在很大程度上统一了客户端程序；而现在移动开发使用不同的系统不同的语言，将来大多数应用必然会统一到一种语言。这种语言必然是html5+javascript.

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