javascript - 在 Dojo 中创建自定义小部件时，在新小部件中调用函数时出错？

Question

问题是我正在遵循教程 here并且新小部件的功能工作正常，直到我将鼠标悬停在从“on”监听器调用 this._changeBackground 方法的小部件上，我收到错误 TypeError: this._changeBackground is not a function

教程中实现的最终代码如下所示:

define(["dojo/_base/declare","dijit/_WidgetBase", "dijit/_TemplatedMixin", "dojo/text!/JS/Allatus/Test.html", "dojo/dom-style", "dojo/_base/fx", "dojo/_base/lang","dojo/on"],
    function(declare, WidgetBase, TemplatedMixin, template, domStyle, baseFx, lang , on){
        return declare([WidgetBase, TemplatedMixin], {
            // Some default values for our author
            // These typically map to whatever you're handing into the constructor
            name: "No Name",
            // Using require.toUrl, we can get a path to our AuthorWidget's space
            // and we want to have a default avatar, just in case
            avatar: require.toUrl("JS/Allatus/custom/android_vector.jpg"),

           bio: "",

            // Our template - important!
            templateString: template,

            // A class to be applied to the root node in our template
            baseClass: "authorWidget",

            // A reference to our background animation
            mouseAnim: null,

            // Colors for our background animation
            baseBackgroundColor: "#fff",
            mouseBackgroundColor: "#def",
            postCreate: function(){
    // Get a DOM node reference for the root of our widget
    var domNode = this.domNode;

    // Run any parent postCreate processes - can be done at any point
    this.inherited(arguments);

    // Set our DOM node's background color to white -
    // smoothes out the mouseenter/leave event animations
    domStyle.set(domNode, "backgroundColor", this.baseBackgroundColor);
    // Set up our mouseenter/leave events - using dojo/on
    // means that our callback will execute with `this` set to our widget
    on(domNode, "mouseenter", function (e) {
        this._changeBackground(this.mouseBackgroundColor);
    });
    on(domNode, "mouseleave", function (e) {
        this._changeBackground(this.baseBackgroundColor);
    });
},
_changeBackground: function(toCol) {
    // If we have an animation, stop it
    if (this.mouseAnim) { this.mouseAnim.stop(); }

    // Set up the new animation
    this.mouseAnim = baseFx.animateProperty({
        node: this.domNode,
        properties: {
            backgroundColor: toCol
        },
        onEnd: lang.hitch(this, function() {
            // Clean up our mouseAnim property
            this.mouseAnim = null;
        })
    }).play();
},
_setAvatarAttr: function(av) {
    // We only want to set it if it's a non-empty string
    if (av != "") {
        // Save it on our widget instance - note that
        // we're using _set, to support anyone using
        // our widget's Watch functionality, to watch values change
        this._set("avatar", av);

        // Using our avatarNode attach point, set its src value
        this.avatarNode.src = av;
    }
}
        });
});

有什么想法为什么我无法在自定义小部件中调用另一个函数？这只是一个错误还是我做错了什么？

Answer 1

您的 mouseEnter 函数在您的小部件范围之外被调用(JS 中的范围指的是“this”变量的值)。这是一个常见的问题，dojo 有一个简单的解决方案，可以使用函数 lang.hitch 将函数绑定(bind)到某个范围。 (而且，我建议阅读有关它的文档)。以下是在这种情况下应如何使用它:

// Set up our mouseenter/leave events - using dojo/on
// means that our callback will execute with `this` set to our widget
on(domNode, "mouseenter", lang.hitch(this, function (e) {
    this._changeBackground(this.mouseBackgroundColor);
}));
on(domNode, "mouseleave", lang.hitch(this, function (e) {
    this._changeBackground(this.baseBackgroundColor);
}));