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

问题描述

虽然大多数苹果文档都写得很好，但我认为 'iOS 事件处理指南' 是一个例外.我很难清楚地理解那里描述的内容.

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.

文件说，

在命中测试中，一个窗口在视图层次结构的最顶层视图上调用hitTest:withEvent:；此方法通过在视图层次结构中返回 YES 的每个视图上递归调用 pointInside:withEvent: 继续进行，向下进行层次结构，直到找到发生触摸的边界内的子视图.该视图成为命中测试视图.

那么是不是系统只调用了最顶层视图的hitTest:withEvent:，它调用了所有子视图的pointInside:withEvent:，如果特定子视图的返回值为 YES，则调用该子视图的子类的 pointInside:withEvent:?

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

这似乎是一个很基本的问题.但我同意你的意见，该文件不像其他文件那样清晰，所以这是我的回答.

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.

hitTest:withEvent: 在 UIResponder 中的实现如下:

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

• 它调用了self
的pointInside:withEvent:
• 如果返回 NO，hitTest:withEvent: 返回 nil.故事的结局.
• 如果返回是 YES，它会发送 hitTest:withEvent: 消息到它的子视图.它从顶级子视图开始，并继续到其他视图，直到一个子视图返回一个非nil 对象，否则所有子视图都会收到消息.
• 如果子视图第一次返回一个非nil 对象，第一个hitTest:withEvent: 返回那个对象.故事的结局.
• 如果没有子视图返回非nil对象，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

这个过程会递归重复，所以通常最终会返回视图层次结构的叶子视图.

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 以做不同的事情.在许多情况下，覆盖 pointInside:withEvent: 更简单，并且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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