如何链接“范围变化”和“更新结束”事件在Dojo？ [英] How to link "extent-change" and "update-end" events in Dojo?

问题描述

在ArcGIS JS API中，在扩展盘更改完成后的处理中，我需要触发一个类的方法。我没有找到任何特殊的事件。当数据尚未加载时，$ code> extent-change 触发得太早了。 update-end 也由我想要调用的函数触发，使得无限循环。所以我需要的是将两个事件联系起来，第二个只是一次。但是如何？

In ArcGIS JS API I need to trigger a method of my class when the processing after an extent change is complete. I didn't find any special event for this. extent-change triggers too early, when the data are not loaded yet. update-end is triggered also by the function I want to call, making an endless loop. So what I need is to link the two events together, the second one just once. But how?

我的大部分活动如下所示：

Most of my events look like this:

this.events.push(on(this.map, "extent-change", lang.hitch(this, this._foo)));

这不适合事件链接，所以我需要使链接的事件有其他的方式。我尝试过：

This is not suitable for event linking, so I need to make the linked event some other way. What I've tried:

_foo: function () {
    function fooEvent() {
        this._bar();
        dojo.disconnect(updateHandle);
    }
    var updateHandle = dojo.connect(map, "onUpdateEnd", fooEvent());
}

_bar 是方法我想在范围变化结束时运行。但是，事件处理程序中的这个意味着别的东西，而不是包含该函数的类。我也尝试了在声明声明中声明的类名，但没有运气。

_bar is the method I want to run on the end of the extent change. However, this in the event handler means something else, not the class containing the function. I also tried the classname I declared in the declare statement, but with no luck.

_foo（）和 _bar（）在同一个类中（让我们称之为foobar / baz code>）。但是，在 fooEvent（）的内部不是我的子类，因为我希望 - 当我尝试使用 this.inherited 在它内，它是未定义的。我尝试的另一种方法是向处理程序添加事件参数，但它也是未定义的。所以除非有更好的方法，否则我需要了解如何获取foobar / baz类的对象。

_foo() and _bar() are in the same class (let's call it "foobar/baz"). However, inside of the fooEvent() is not its subclass as I hoped - when I try to use this.inherited within it, it's undefined. Another way I try is to add event argument to the handler, but it's undefined as well. So unless there is some better way, I need to understand how to get the object of "foobar/baz" class.

另一种尝试方法是使用 lang.hitch ，以下列方式之一：

Another way I tried was to use lang.hitch once more, in one of the following ways:

//through the cluster event
var updateHandle = dojo.connect(map, "onUpdateEnd", lang.hitch(this, clusterEvent));

//or directly calling _bar()
var updateHandle = dojo.connect(map, "onUpdateEnd", { langh:lang.hitch(this, this._bar), disc:dojo.disconnect(updateHandle)});

//or through on, leaving a rouge event listener
dojo.on(map, "onUpdateEnd", lang.hitch(this, this._bar));

没有一个返回任何清除错误，虽然 _bar（）方法似乎工作了一段时间，它现在不起作用 - 对于以前的所有三个都是如此。我不明白这些听众的作用。

None of them returns any clear error and though the _bar() method seemed to work for some time, it doesn't work now - this is true for all three of the previous. I don't understand what these listeners do.

推荐答案

我通过展平事件听众来解决这个问题。首先，我将一个标志 _reloadFlag ，在构造函数中初始化为 false ，然后更改为只要我想要调用 _bar ，就像在 _foo 中一样。 _bar 现在开始测试 _reloadFlag 将其设置为 false 或什么也不返回事件侦听器现在看起来像这样：

I solved this issue by flattening the event listeners. First, I made a flag _reloadFlag, initialized in the constructor as false and then changed to true whenever I want to call _bar, like in _foo. _bar now starts with a test of _reloadFlag either setting it to false or returning nothing. The event listeners now look like this:

this.events.push(on(this.map, "extent-change", lang.hitch(this, this._foo)));
this.events.push(on(this.map, "update-end", lang.hitch(this, this._bar)));

这篇关于如何链接“范围变化”和“更新结束”事件在Dojo？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！