• Html5实现loading功能
  • 银色镜架 发表于 2015/7/5 12:49:00 | 分类标签: html5 loading web2.0
  •  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。

    所以就看了一点html5的东东,并研究了一下canvas标签的用法。如果你从来没有用过canvas标签,请参考Html5 canvas cheat sheet。

    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。

    废话少叙,我们先来看下这两个loading图标的效果,注意,如果你用的是PC,请使用Firefox,Opera或者IE9看此效果。


    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。

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    <!doctype html>
    <html>
      <head>
        <meta http-equiv="content-type" content="GBK"/>
        <title>loading</title>
        <script type="text/javascript">
       
        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" onclick="loadingObj.hide()" value="HideLoading"/>
        <input type="button" onclick="loadingObj.show()" value="showLoading"/>
        </p>
        <script>
        var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3});
        loadingObj.show();
        </script>
      </body>
    </html>
    ,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。
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    <!doctype html>
    <html>
    <head>
      <meta http-equiv="content-type" content="text/html;charset=gbk"/>
      <title>loading</title>
      <script>
        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" onclick="loadingObj.hide()" value="HideLoading"/>
        <input type="button" onclick="loadingObj.show()" 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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