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利用HTML5 Canvas制作键盘及鼠标动画的实例分享_html5教程技巧

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Release： 2016-05-16 15:45:44
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键盘控制小球移动

众所周知，我们所看到的动画实际上就是一系列静态画面快速切换，从而让肉眼因视觉残像产生了「画面在活动」的视觉效果。明白了这一点后，在canvas上绘制动画效果就显得比较简单了。我们只需要将某个静态图形先清除，然后在另外一个位置重新绘制，如此反复，让静态图形按照一定的轨迹进行移动，就可以产生动画效果了。

下面，我们在canvas上绘制一个实心小球，然后用键盘上的方向键控制小球的移动，从而产生动态效果。示例代码如下：

JavaScript Code 复制内容到剪贴板
  1. nbsp;html>
  4. "UTF-8">
  5. html5 canvas绘制可移动的小球入门示例
  7. "moveBall(event)">
  10. "myCanvas" width= "400px" height= "300px" style= "border: 1px solid red;" >
  11. 您的浏览器不支持canvas标签。
  14. >
  15. //获取Canvas对象(画布)
  16. varcanvas = document.getElementById("myCanvas");
  18. //表示圆球的类
  19. functionBall(x, y ,radius, speed){
  20. this.x = x || 10;//圆球的x坐标，默认为10
  21. this.y = y || 10;//圆球的y坐标，默认为10
  22. this.radius = radius || 10;//圆球的半径，默认为10
  23. this.speed = speed || 5;//圆球的移动速度，默认为5
  25. //向上移动
  26. this.moveUp =function(){
  27. this.y -=this.speed;
  28. if(this.ythis.radius){
  29. //防止超出上边界
  30. this.y =this.radius;
  31. }
  32. };
  34. //向右移动
  35. this.moveRight =function(){
  36. this.x +=this.speed;
  37. varmaxX = canvas.width -this.radius;
  38. if(this.x > maxX){
  39. //防止超出右边界
  40. this.x = maxX;
  41. }
  42. };
  44. //向左移动
  45. this.moveLeft =function(){
  46. this.x -=this.speed;
  47. if(this.xthis.radius){
  48. //防止超出左边界
  49. this.x =this.radius;
  50. }
  51. };
  53. //向下移动
  54. this.moveDown =function(){
  55. this.y +=this.speed;
  56. varmaxY = canvas.height -this.radius;
  57. if(this.y > maxY){
  58. //防止超出下边界
  59. this.y = maxY;
  60. }
  61. };
  62. }
  64. //绘制小球
  65. functiondrawBall(ball){
  66. if(typeofctx !="undefined"){
  67. ctx.beginPath();
  68. ctx.arc(ball.x, ball.y, ball.radius, 0, Math.PI * 2,false);
  69. ctx.fill();
  70. }
  71. }
  73. //清空canvas画布
  74. functionclearCanvas(){
  75. if(typeofctx !="undefined"){
  76. ctx.clearRect(0, 0, 400, 300);
  77. }
  78. }
  80. varball =newBall();
  81. //简单地检测当前浏览器是否支持Canvas对象，以免在一些不支持html5的浏览器中提示语法错误
  82. if(canvas.getContext){
  83. //获取对应的CanvasRenderingContext2D对象(画笔)
  84. varctx = canvas.getContext("2d");
  85. drawBall(ball);
  86. }
  88. //onkeydown事件的回调处理函数
  89. //根据用户的按键来控制小球的移动
  90. functionmoveBall(event){
  91. switch(event.keyCode){
  92. case37://左方向键
  93. ball.moveLeft();
  94. break;
  95. case38://上方向键
  96. ball.moveUp();
  97. break;
  98. case39://右方向键
  99. ball.moveRight();
  100. break;
  101. case40://下方向键
  102. ball.moveDown();
  103. break;
  104. default://其他按键操作不响应
  105. return;
  106. }
  108. clearCanvas();//先清空画布
  109. drawBall(ball);//再绘制最新的小球
  110. }

请使用支持html5的浏览器打开以下网页以查看实际效果(使用方向键进行移动)：
使用canvas绘制可移动的小球。


小丑笑脸
只需要了解很少的几个API，然后使用需要的动画参数，就能制作出这个有趣又能响应你的动作的Web动画。
第一步，画五官

这个小丑没有耳朵和眉毛，所以只剩下三官，但它的两个眼睛我们要分别绘制，所以一共是四个部分。下面先看看代码。

绘制左眼的代码

JavaScript Code 复制内容到剪贴板
  1. varleftEye =newKinetic.Line({
  2. x: 150,
  3. points: [0, 200, 50, 190, 100, 200, 50, 210],
  4. tension: 0.5,
  5. closed:true,
  6. stroke:'white',
  7. strokeWidth: 10
  8. });

绘制右眼的代码

JavaScript Code 复制内容到剪贴板
  1. varrightEye =newKinetic.Line({
  2. x: sw - 250,
  3. points: [0, 200, 50, 190, 100, 200, 50, 210],
  4. tension: 0.5,
  5. closed:true,
  6. stroke:'white',
  7. strokeWidth: 10
  8. });

绘制鼻子的代码

JavaScript Code 复制内容到剪贴板
  1. varnose =newKinetic.Line({
  2. points: [240, 280, sw/2, 300, sw-240,280],
  3. tension: 0.5,
  4. closed:true,
  5. stroke:'white',
  6. strokeWidth: 10
  7. });

绘制嘴巴的代码

JavaScript Code 复制内容到剪贴板
  1. varmouth =newKinetic.Line({
  2. points: [150, 340, sw/2, 380, sw - 150, 340, sw/2, sh],
  3. tension: 0.5,
  4. closed:true,
  5. stroke:'red',
  6. strokeWidth: 10
  7. });

你会不会觉得很失望，原来就这么简单几行代码。没错，就是这么简单，相信你对自己能成为一名Web游戏动画程序员开始有信心了!

简单讲解一下上面的代码。Kinetic就是我们使用的js工具包。在页面的头部，我们需要这样引用它：

JavaScript Code 复制内容到剪贴板
  1. varmouth =newKinetic.Line({
  2. points: [150, 340, sw/2, 380, sw - 150, 340, sw/2, sh],
  3. tension: 0.5,
  4. closed:true,
  5. stroke:'red',
  6. strokeWidth: 10
  7. });

其它几个分别是几个关键点，线条弹性，颜色，宽度等。这些都很容易理解。

第二步，让图动起来

这个动画之所以能吸引人，是因为它能响应你的鼠标动作，和用户有互动，这是一个成功的动画最关键的地方。如果你仔细观察，这个小丑五官的变化只是形状的变化，眼睛变大，嘴巴变大，鼻子变大，但特别的是这个变化不是瞬间变化，而是有过渡性的，这里面有一些算法，这就是最让人发愁的地方。幸运的是，这算法技术都非常的成熟，不需要我们来思考，在这些动画引擎库里都把这些技术封装成了非常简单方便的接口。下面我们来看看如何让动起来。

左眼的动画

JavaScript Code 复制内容到剪贴板
  1. varleftEyeTween =newKinetic.Tween({
  2. node: leftEye,
  3. duration: 1,
  4. easing: Kinetic.Easings.ElasticEaseOut,
  5. y: -100,
  6. points: [0, 200, 50, 150, 100, 200, 50, 200]
  7. });

右眼的动画

JavaScript Code 复制内容到剪贴板
  1. varrightEyeTween =newKinetic.Tween({
  2. node: rightEye,
  3. duration: 1,
  4. easing: Kinetic.Easings.ElasticEaseOut,
  5. y: -100,
  6. points: [0, 200, 50, 150, 100, 200, 50, 200]
  7. });

鼻子的动画

JavaScript Code 复制内容到剪贴板
  1. varnoseTween =newKinetic.Tween({
  2. node: nose,
  3. duration: 1,
  4. easing: Kinetic.Easings.ElasticEaseOut,
  5. y: -100,
  6. points: [220, 280, sw/2, 200, sw-220,280]
  7. });

嘴巴的动画

JavaScript Code 复制内容到剪贴板
  1. varmouthTween =newKinetic.Tween({
  2. node: mouth,
  3. duration: 1,
  4. easing: Kinetic.Easings.ElasticEaseOut,
  5. points: [100, 250, sw/2, 250, sw - 100, 250, sw/2, sh-20]
  6. });

这些代码非常的简单，而且变量名能自释其意。稍微有点经验的程序员想看懂这些代码应该不难。基本每段代码都是让你提供一些点，指定动画动作的衰退模式和持续时间。

完整的动画代码

JavaScript Code 复制内容到剪贴板
  1. nbsp;HTML>
  5. body {
  6. margin: 0px;
  7. padding: 0px;
  8. }
  9. #container {
  10. background-color: black;
  11. }
  15. "container" >
  16. >
  17. >
  18. varsw = 578;
  19. varsh = 400;
  20. varstage =newKinetic.Stage({
  21. container:'container',
  22. width: 578,
  23. height: 400
  24. });
  25. varlayer =newKinetic.Layer({
  26. y: -30
  27. });
  29. varleftEye =newKinetic.Line({
  30. x: 150,
  31. points: [0, 200, 50, 190, 100, 200, 50, 210],
  32. tension: 0.5,
  33. closed:true,
  34. stroke:'white',
  35. strokeWidth: 10
  36. });
  38. varrightEye =newKinetic.Line({
  39. x: sw - 250,
  40. points: [0, 200, 50, 190, 100, 200, 50, 210],
  41. tension: 0.5,
  42. closed:true,
  43. stroke:'white',
  44. strokeWidth: 10
  45. });
  47. varnose =newKinetic.Line({
  48. points: [240, 280, sw/2, 300, sw-240,280],
  49. tension: 0.5,
  50. closed:true,
  51. stroke:'white',
  52. strokeWidth: 10
  53. });
  55. varmouth =newKinetic.Line({
  56. points: [150, 340, sw/2, 380, sw - 150, 340, sw/2, sh],
  57. tension: 0.5,
  58. closed:true,
  59. stroke:'red',
  60. strokeWidth: 10
  61. });
  63. layer.add(leftEye)
  64. .add(rightEye)
  65. .add(nose)
  66. .add(mouth);
  68. stage.add(layer);
  70. // tweens
  72. varleftEyeTween =newKinetic.Tween({
  73. node: leftEye,
  74. duration: 1,
  75. easing: Kinetic.Easings.ElasticEaseOut,
  76. y: -100,
  77. points: [0, 200, 50, 150, 100, 200, 50, 200]
  78. });
  80. varrightEyeTween =newKinetic.Tween({
  81. node: rightEye,
  82. duration: 1,
  83. easing: Kinetic.Easings.ElasticEaseOut,
  84. y: -100,
  85. points: [0, 200, 50, 150, 100, 200, 50, 200]
  86. });
  88. varnoseTween =newKinetic.Tween({
  89. node: nose,
  90. duration: 1,
  91. easing: Kinetic.Easings.ElasticEaseOut,
  92. y: -100,
  93. points: [220, 280, sw/2, 200, sw-220,280]
  94. });
  96. varmouthTween =newKinetic.Tween({
  97. node: mouth,
  98. duration: 1,
  99. easing: Kinetic.Easings.ElasticEaseOut,
  100. points: [100, 250, sw/2, 250, sw - 100, 250, sw/2, sh-20]
  101. });
  103. stage.getContainer().addEventListener('mouseover',function() {
  104. leftEyeTween.play();
  105. rightEyeTween.play();
  106. noseTween.play();
  107. mouthTween.play();
  108. });
  110. stage.getContainer().addEventListener('mouseout',function() {
  111. leftEyeTween.reverse();
  112. rightEyeTween.reverse();
  113. noseTween.reverse();
  114. mouthTween.reverse();
  115. });

观看演示

Related labels：
canvas html5 animation
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