在javascript画布上移动图像
我正在尝试制作一个非常简单的动画,加载到Javascript画布上的图像只是向右滑动。以下代码适用于绘制的矩形,但当我尝试插入图像时,不会加载任何内容,但不会收到任何错误消息。我需要让它只使用Javascript在javascript画布上移动图像,javascript,image,canvas,Javascript,Image,Canvas,我正在尝试制作一个非常简单的动画,加载到Javascript画布上的图像只是向右滑动。以下代码适用于绘制的矩形,但当我尝试插入图像时,不会加载任何内容,但不会收到任何错误消息。我需要让它只使用Javascript window.requestAnimFrame = (function(){ return window.requestAnimationFrame || window.webkitRequestAnimationFrame ||
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
var canvas = document.getElementById("canvas"),
cx = canvas.getContext("2d");
function Card(x,y){
this.x = x || 0;
this.y = y || 0;
this.draw = function(){
var img = new Image();
img.onload = function()
{
cx.drawImage(img, x, y);
}
img.src = "images/back.jpg";
}
}
var myCard = new Card(50,50);
function loop(){
cx.clearRect(0, 0, canvas.width, canvas.height);
myCard.x++;
myCard.draw();
requestAnimFrame(loop);
}
loop();
问题是[x,y]值在draw函数中未定义 演示: 下面是对代码的重构,以使其保持在适当的范围内:
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; }
#canvas{border:1px solid red;}
</style>
<script>
$(function(){
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
var canvas = document.getElementById("canvas"),
cx = canvas.getContext("2d");
function Card(x,y){
this.x = x || 0;
this.y = y || 0;
this.img=new Image();
this.init=function(){
// "var self=this" makes myCard available in the img.onload function
// otherwise "this" inside img.onload refers to the img
var self=this;
this.img.onload = function()
{
self.draw();
loop();
}
this.img.src = "https://dl.dropboxusercontent.com/u/139992952/stackoverflow/house16x16.png";
}
// x,y need to be this.x and this.y
this.draw = function(){
cx.drawImage(this.img, this.x, this.y);
}
}
var myCard = new Card(50,50);
myCard.init();
function loop(){
if(myCard.x<canvas.width-20){
requestAnimFrame(loop);
}
cx.clearRect(0, 0, canvas.width, canvas.height);
myCard.x++;
myCard.draw();
}
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>
正文{背景色:象牙;}
#画布{边框:1px纯红;}
$(函数(){
window.requestAnimFrame=(函数(){
return window.requestAnimationFrame||
window.webkitRequestAnimationFrame||
window.mozRequestAnimationFrame||
window.oRequestAnimationFrame||
window.msRequestAnimationFrame||
函数(回调){
设置超时(回调,1000/60);
};
})();
var canvas=document.getElementById(“canvas”),
cx=canvas.getContext(“2d”);
功能卡(x,y){
这个.x=x | | 0;
这个.y=y | | 0;
this.img=新图像();
this.init=函数(){
//“var self=this”使myCard在img.onload函数中可用
//否则,img.onload中的“this”指的是img
var self=这个;
this.img.onload=函数()
{
self.draw();
loop();
}
this.img.src=”https://dl.dropboxusercontent.com/u/139992952/stackoverflow/house16x16.png";
}
//x,y必须是这个,x和这个
this.draw=函数(){
cx.drawImage(this.img、this.x、this.y);
}
}
var myCard=新卡(50,50);
myCard.init();
函数循环(){
如果(myCard.x