ios - 为什么 UIViewController 和 UIView 子类 UIResponder？

Question

看苹果GLPaint示例代码。

我看到 PaintingViewController 和 PaintingView 都实现了

- (BOOL)canBecomeFirstResponder {
    return YES;
}

为什么是二元性？一般来说，不应该只有 UIView 负责处理硬件产生的触摸事件吗？如 The Runtime Interaction Model for Views 中所述

Answer 1

不，有一个简单的例子:

想象一下，你有一个 presentedController .那么你不想要 presentingController处理触摸事件，即使它仍然可见。

View Controller 层次结构在事件传递中非常重要。

见 UIViewController 中的注释文档:

A view controller is tightly bound to the views it manages and takes part in the responder chain used to handle events. View controllers are also UIResponder objects and are inserted into the responder chain between the view controller’s root view and that view’s superview, which typically belongs to a different view controller. If none of the view controller’s views handle an event, the view controller has the option of handling the event or passing it along to the superview.