iOS Autolayout - viewDidLayoutSubviews 中未设置帧大小 [英] iOS Autolayout - Frame size not set in viewDidLayoutSubviews

问题描述

我正在开发 iOS 8 的键盘，使用 Autolayout 将按钮放置在视图上.
当我使用约束更改布局时，屏幕上的所有内容都正确显示，但是当我想知道视图的帧大小时，我没有得到正确的大小.

I'm working on a keyboard for iOS 8 using Autolayout to place the buttons on the view.
When I'm changing the layout using constraints, everything is appearing correctly on the screen, but when I want to know the view's frame size, I don't get the right size.

例如:我按下一个键，键盘布局会根据我的约束改变和布局.然后我想知道屏幕上任何按钮的大小 - 我在viewDidLayoutSubviews"中执行此操作并在控制台中获得结果:

For example: I press a key, the keyboard layout changes and layouts everything according to my constraints. Then I want to know the size of any button on the screen - I do that in "viewDidLayoutSubviews" and get that result in the console:

2014-10-29 12:27:09.088 Keyboard[2193:60674] view did layout subviews
2014-10-29 12:27:09.088 Keyboard[2193:60674] {{inf, inf}, {0, 0}}

按钮具有正确的大小和正确的位置，但是在尝试获取其框架时未设置大小.

The button has the correct size and correct position, but when trying to get its frame the size is not set.

当我的代码在 viewDidLayoutSubviews 中不起作用时，我必须把它放在哪里?

Where do I have to put my code when it is not working in viewDidLayoutSubviews?

我在 stackoverflow 和其他网站上发现了很多问题，但没有一个涵盖我的问题.

I found a lot of questions on stackoverflow and other websited, but none of them covered my question.

推荐答案

我遇到了一个非常相似的问题(upvoted question)，发现 beeef's回答 指向正确的方向.鉴于 Apple 的文档说不要直接调用 layoutSubviews()，我改为执行以下操作(其中 mySubView 是 self.view 的直接子视图):

I encountered a very similar issue (upvoted question) and found beeef's answer to point in the right direction. Given that Apple's documentation says not to call layoutSubviews() directly, I instead did as follows (where mySubView is a direct subview of self.view):

override func viewDidLayoutSubviews() {
    // self.view's direct subviews are laid out.
    // force my subview to layout its subviews:
    self.mySubView.setNeedsLayout()
    self.mySubView.layoutIfNeeded()

    // here we can get the frame of subviews of mySubView
    // and do useful things with that...
}

仅供参考，在我的情况下，mySubView 是一个 UIScrollView，我需要获取其中一个子视图的框架，以便我可以在视图出现之前相应地设置 contentOffset.我不确定 viewDidLayoutSubviews() 是否是执行此操作的最佳位置，但它可以确保 mySubView 已布局.

Just FYI, in my case mySubView is a UIScrollView, and I need to get the frame of one of its subviews, such that I can set the contentOffset accordingly before the view appears. I'm not sure whether viewDidLayoutSubviews() is the best place to do this, but it ensures that mySubView has been laid out.

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