Question

这给我带来了营养——我一直在圈子里,这是不受欢迎的。我装上了多种动态图像,并有一个简单的 Java字标语,我对每个图像都进行了即时检查,一旦图像装满同步,就会有倒退。

I have verified that the callback code works just fine on a stand-alone basis (ie. I can call the callback manually after the image has loaded, and the image is rendered correctly), and I have verified that the image itself is successfully loaded (by switching the object s callback for a simple one line logging function), but when I try to tie it all together, the callback apparently never gets invoked.

我对联合材料说得较新,我怀疑,我缺少一些关于目标内职能定义的基本内容,但尽管有很多戈格罗宁,我还是可以做些什么。

请有人告诉我我我我我,我的方法有误?

function ImageHolder(aX,aY,aW,aH, anImageURL) {
    this.posx=aX;
    this.posy=aY;
    this.posw=aW;
    this.posh=aH;
    this.url=anImageURL;

    this.myImage = new Image();
    this.myImage.onload=this.onload;
    this.myImage.src=anImageURL;
    this.onload=function() {

        try {
            var d=document.getElementById("d");
            var mycanvas=d.getContext( 2d );
            mycanvas.drawImage(this.myImage, this.posx, this.posy, this.posw, this.posh);
            } catch(err) {
                console.log( Onload: could not draw image  +this.url);
                console.log(err);
            }
    };
}

Answer 1

你们有两个问题:首先,this.onload没有在你把它分配给形象的时候加以界定。您可以通过在存储<代码>onload的左手作为this的财产而加以确定。第二个问题是,当<代码>上载手稿功能被称作时,this并不适用于你认为的(事实上,它提到了刚刚装满的<代码>Image。您需要将目前<代码>(ImageHolder)的标语和用法放在“密码”栏目中。

新法典:

var that = this;

this.myImage = new Image();
this.myImage.onload=function() {
    try {
        var d=document.getElementById("d");
        var mycanvas=d.getContext( 2d );
        mycanvas.drawImage(that.myImage, that.posx, that.posy, that.posw, that.posh);
    } catch(err) {
        console.log( Onload: could not draw image  +that.url);
        console.log(err);
    }
};
this.myImage.src = anImageURL;

友情链接