javascript - 图片源无效错误

Question

var nodeIconImg = new Image();
nodeIconImg.onload = function () {

    var nodeIcon = new Kinetic.Image({
        image: nodeIconImg,
        width: 30,
        height: 30
    });
}

var url = '<?= $baseurl; ?>/img/' + node.main_photo;
nodeIconImg.src = url;

这是kinetic.js中发生错误的核心代码行(恰好在drawImage方法中):

drawImage: function () {
    var a = arguments,
        b = this._context;
    3 === a.length ? b.drawImage(a[0], a[1], a[2]) : 5 === a.length ? b.drawImage(a[0], a[1], a[2], a[3], a[4]) : 9 === a.length && b.drawImage(a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8])
}

错误信息是:

Uncaught InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable.

有什么想法吗？有人遇到过这个问题吗？

Answer 1

onload 函数完成后，您的 nodeIcon 不在范围内。

因此，当您稍后在代码中尝试使用 nodeIcon 时，它不再定义并引发错误。

您需要在 onload 函数外部声明 var nodeIcon

var nodeIcon;

var nodeIconImg = new Image();
nodeIconImg.onload = function () {

    nodeIcon = new Kinetic.Image({
        image: nodeIconImg,
        width: 30,
        height: 30
    });

}
var url = "ship.png";
nodeIconImg.src = url;

或者将nodeIcon添加到onload函数内的图层

var nodeIconImg = new Image();
nodeIconImg.onload = function () {

    var nodeIcon = new Kinetic.Image({
        image: nodeIconImg,
        width: 30,
        height: 30
    });
    layer.add(nodeIcon);
    layer.draw();

}
var url = "ship.png";
nodeIconImg.src = url;