html5 loading 效果来了
html5 loading 效果来了
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。
Html代码1.<!doctype html>
2.<html>
3.<head>
4. <meta http-equiv="content-type" content="GBK"/>
5. <title>loading</title>
6. <script type="text/javascript">
7. /*
8. html5 loading 控件
11. */
12. function loading(canvas,options){
13. this.canvas = canvas;
14. if(options){
15. this.radius = options.radius||12;
16. this.circleLineWidth = options.circleLineWidth||4;
17. this.circleColor = options.circleColor||'lightgray';
18. this.dotColor = options.dotColor||'gray';
19. }else{
20. this.radius = 12;
21. this.circelLineWidth = 4;
22. this.circleColor = 'lightgray';
23. this.dotColor = 'gray';
24. }
25. }
26. loading.prototype = {
27. show:function (){
28. var canvas = this.canvas;
29. if(!canvas.getContext)return;
30. if(canvas.__loading)return;
31. canvas.__loading = this;
32. var ctx = canvas.getContext('2d');
33. var radius = this.radius;
34. var rotators = [{angle:0,radius:1.5},{angle:3/radius,radius:2},{angle:7/radius,radius:2.5},{angle:12/radius,radius:3}];
35. var me = this;
36. canvas.loadingInterval = setInterval(function(){
37. ctx.clearRect(0,0,canvas.width,canvas.height);
38. var lineWidth = me.circleLineWidth;
39. var center = {x:canvas.width/2 - radius,y:canvas.height/2-radius};
40. ctx.beginPath();
41. ctx.lineWidth = lineWidth;
42. ctx.strokeStyle = me.circleColor;
43. ctx.arc(center.x,center.y,radius,0,Math.PI*2);
44. ctx.closePath();
45. ctx.stroke();
46. for(var i=0;i<rotators.length;i++){
47. var rotatorAngle = rotators.currentAngle||rotators.angle;
48. //在圆圈上面画小圆
49. var rotatorCenter = {x:center.x-(radius)*Math.cos(rotatorAngle) ,y:center.y-(radius)*Math.sin(rotatorAngle)};
50. var rotatorRadius = rotators.radius;
51. ctx.beginPath();
52. ctx.fillStyle = me.dotColor;
53. ctx.arc(rotatorCenter.x,rotatorCenter.y,rotatorRadius,0,Math.PI*2);
54. ctx.closePath();
55. ctx.fill();
56. rotators.currentAngle = rotatorAngle+4/radius;
57. }
58. },50);
59. },
60. hide:function(){
61. var canvas = this.canvas;
62. canvas.__loading = false;
63. if(canvas.loadingInterval){
64. window.clearInterval(canvas.loadingInterval);
65. }
66. var ctx = canvas.getContext('2d');
67. if(ctx)ctx.clearRect(0,0,canvas.width,canvas.height);
68. }
69. };
70.
71. </script>
72.</head>
73.<body>
74. <canvas id="canvas" width="300" height="100" style="border:1px solid #69c"></canvas>
75. <p>
76. <input type="button" onclick="loadingObj.hide()" value="HideLoading"/>
77. <input type="button" onclick="loadingObj.show()" value="showLoading"/>
78. </p>
79. <script>
80. var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3});
81. loadingObj.show();
82. </script>
83.</body>
84.</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。
Html代码1.<!doctype html>
2.<html>
3.<head>
4.<meta http-equiv="content-type" content="text/html;charset=gbk"/>
5.<title>loading</title>
6.<script>
7. /*
8. html5 loading 控件
12. function loading(canvas,options){
13. this.canvas = canvas;
14. if(options){
15. this.radius = options.radius||12;
16. this.circleLineWidth = options.circleLineWidth||4;
17. this.circleColor = options.circleColor||'lightgray';
18. this.moveArcColor = options.moveArcColor||'gray';
19. }else{
20. this.radius = 12;
21. this.circelLineWidth = 4;
22. this.circleColor = 'lightgray';
23. this.moveArcColor = 'gray';
24. }
25. }
26. loading.prototype = {
27. show:function (){
28. var canvas = this.canvas;
29. if(!canvas.getContext)return;
30. if(canvas.__loading)return;
31. canvas.__loading = this;
32. var ctx = canvas.getContext('2d');
33. var radius = this.radius;
34. var me = this;
35. var rotatorAngle = Math.PI*1.5;
36. var step = Math.PI/6;
37. canvas.loadingInterval = setInterval(function(){
38. ctx.clearRect(0,0,canvas.width,canvas.height);
39. var lineWidth = me.circleLineWidth;
40. var center = {x:canvas.width/2 - radius,y:canvas.height/2-radius};
41. ctx.beginPath();
42. ctx.lineWidth = lineWidth;
43. ctx.strokeStyle = me.circleColor;
44. ctx.arc(center.x,center.y,radius,0,Math.PI*2);
45. ctx.closePath();
46. ctx.stroke();
47. //在圆圈上面画小圆
48. ctx.beginPath();
49. ctx.strokeStyle = me.moveArcColor;
50. ctx.arc(center.x,center.y,radius,rotatorAngle,rotatorAngle+Math.PI*.45);
51. ctx.stroke();
52. rotatorAngle+=step;
53.
54. },50);
55. },
56. hide:function(){
57. var canvas = this.canvas;
58. canvas.__loading = false;
59. if(canvas.loadingInterval){
60. window.clearInterval(canvas.loadingInterval);
61. }
62. var ctx = canvas.getContext('2d');
63. if(ctx)ctx.clearRect(0,0,canvas.width,canvas.height);
64. }
65. };
66.
67. </script>
68.</head>
69.<body>
70. <canvas id="canvas" width="300" height="100" style="border:1px solid #69c">您的浏览器不支持html5哟</canvas>
71. <p>
72. <input type="button" onclick="loadingObj.hide()" value="HideLoading"/>
73. <input type="button" onclick="loadingObj.show()" value="showLoading"/>
74. </p>
75. <script>
76. var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3});
77. loadingObj.show();
78. </script>
79.</body>
80.</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.
学习鸟 谢谢分享
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