iOS的事件处理 - hitTest：withEvent：和pointInside：withEvent：如何相关？

问题描述

虽然大多数苹果文档编写得很好，但我认为'是一个例外。我很难清楚地了解那里所描述的内容。

While most apple documents are very well written, I think 'Event Handling Guide for iOS' is an exception. It's hard for me to clearly understand what's been described there.

该文件说，

因此只有 hitTest：withEvent：由系统调用，它调用所有子视图的 pointInside：withEvent：，如果从特定子视图返回的是是，然后调用 pointInside：withEvent：该子视图的子类？

So is it like that only hitTest:withEvent: of the top-most view is called by the system, which calls pointInside:withEvent: of all of subviews, and if the return from a specific subview is YES, then calls pointInside:withEvent: of that subview's subclasses?

推荐答案

这似乎是一个非常基本的问题。但我同意你的意见，文件不像其他文件那么清楚，所以这是我的答案。

It seems quite a basic question. But I agree with you the document is not as clear as other documents, so here is my answer.

在UIResponder中执行 hitTest：withEvent：会执行以下操作：

The implementation of hitTest:withEvent: in UIResponder does the following:

• 它调用 pointInside：withEvent： of self


• 如果返回为NO，则 hitTest：withEvent：返回 nil 。故事的结尾。


• 如果返回是YES，它会将 hitTest：withEvent：消息发送到其子视图。
  它从顶级子视图开始，并继续到其他视图，直到子视图
  返回非 nil 对象，或者所有子视图都接收到消息。


• 如果子视图第一次返回非 nil 对象，则第一个 hitTest： withEvent：返回该对象。故事结束。


• 如果没有子视图返回非 nil 对象，则第一个 hitTest： withEvent：返回 self

• It calls pointInside:withEvent: of self
• If the return is NO, hitTest:withEvent: returns nil. the end of the story.
• If the return is YES, it sends hitTest:withEvent: messages to its subviews.it starts from the top-level subview, and continues to other views until a subviewreturns a non-nil object, or all subviews receive the message.
• If a subview returns a non-nil object in the first time, the first hitTest:withEvent: returns that object. the end of the story.
• If no subview returns a non-nil object, the first hitTest:withEvent: returns self

此过程重复递归地，通常最终返回视图层次结构的叶视图。

This process repeats recursively, so normally the leaf view of the view hierarchy is returned eventually.

但是，您可以覆盖 hitTest：withEvent 以不同的方式做某事。在许多情况下，覆盖 pointInside：withEvent：更简单，仍然提供足够的选项来调整应用程序中的事件处理。

However, you might override hitTest:withEvent to do something differently. In many cases, overriding pointInside:withEvent: is simpler and still provides enough options to tweak event handling in your application.

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