iOS的自动布局 - 帧大小viewDidLayoutSubviews未设定 [英] iOS Autolayout - Frame size not set in viewDidLayoutSubviews

问题描述

我正在键盘上适用于iOS 8使用自动布局放置在视图上的按钮。结果
当我使用约束更改布局，一切都正确出现在屏幕上，但是当我想知道视图的帧大小，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：我根据我的约束preSS一键，键盘布​​局的变化和布局的一切。然后，我想知道屏幕上的任何按钮的大小 - 我这样做，在viewDidLayoutSubviews，并得到这一结果在控制台：

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上，而是试图获取其帧时没有设置大小。

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

在哪里我已经把我的code时，它不是在viewDidLayoutSubviews工作？

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

我发现了很多的websited在计算器和其他问题，但他们没有覆盖我的问题。

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

推荐答案

我遇到了一个非常类似的问题（upvoted的问题），并发现 beeef的回答在正确的方向指向。鉴于苹果的文件说，不要调用layoutSubviews（）直接，而不是我做了如下（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mySubView是一个UIScrollView，我需要得到它的子视图中的一个，这样我可以设置相应的contentOffset出现视图之前的框架。我不知道viewDidLayoutSubviews（）是否做到这一点的最佳场所，但它可以确保mySubView已经奠定了。

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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