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实现懒惰拖放

[英]Implement lazy drag & drop

原文 2010-09-14 12:56:05 3 2 c#/ drag-and-drop/ lazy-evaluation

I am trying to implement a lazy drag and drop operation. 我正在尝试实现一个懒惰的拖放操作。 I want to show a listview with files to my user, when the user drags a file and drops it into a folder the content should be downloaded and delivered. 我想向用户显示包含文件的列表视图，当用户拖动文件并将其放入文件夹时，应下载并传送内容。

I am using the IDataObject interface, but my problem is that the GetData() method is queried way too early. 我正在使用IDataObject接口，但我的问题是过早地查询GetData（）方法。 For instance a drag over the desktop (without any drop involved) will query the GetData() method a couple of times. 例如，在桌面上拖动（不涉及任何丢弃）将多次查询GetData（）方法。 And each of these calls starts the download of the file :/ 每个调用都会开始下载文件：/

Now, my question is: What's wrong here - why is the GetData() method called without any drop? 现在，我的问题是：这里有什么问题 - 为什么调用GetData（）方法没有任何丢弃？ Is there another way to implement lazy drag & drop operations in .net? 还有另一种在.net中实现懒惰拖放操作的方法吗？

2 个解决方案

Maybe this could work for you... 也许这对你有用......

On every occurrence of the GetData() do this: 每次出现GetData（）时都会这样做：

you'll need some kind of a timer here. 你在这里需要某种计时器。
if your timer is already active, kill it. 如果您的计时器已经激活，请将其杀死。
create and start a new timer. 创建并启动一个新计时器。 Make it 1sec or determine its duration from the experiment. 将其设为1秒或从实验中确定其持续时间。
on timer event do what has to be done. 在计时器事件上做必须做的事情。

I use similar procedure on many occasions where such workaround is needed. 我需要在需要这种解决方法的许多场合使用类似的程序。

I think GetData is being called so that the (potential) drop target can determine whether or not it can accept the (potential) drop item(s). 我认为正在调用GetData，以便（潜在的）放置目标可以确定它是否可以接受（潜在的）放置项。 Have you considered using a shell extension? 你考虑过使用shell扩展吗？