UICollectionView自动调整高度 [英] UICollectionView autosize height

问题描述

如何正确调整UICollectionView的大小以使其完全显示其内容？我尝试了很多东西，包括设置框架，调用 reloadData 并使布局无效：

How do I properly resize a UICollectionView so that it fully displays its contents? I have tried many things, including setting its frame, calling reloadData and invalidating the layout:

self.collectionView.contentSize = CGSizeMake(300, 2000);
self.collectionView.frame = CGRectMake(0, 0, 300, 2000);
[self.collectionView reloadData];
[self.collectionView.collectionViewLayout invalidateLayout];

但这些都没有任何影响。按下按钮后，我仍然看到初始视图，如下所示：

but none of this has any effect. After pressing the button I still see the initial view, like this:

我有一个小型演示程序，其中我有一个产生100个元素的数据源。在Interface Builder中，我最初将UICollectionView的大小设置为一个较小的值，以便不是所有元素都适合，之后我按下一个按钮，然后执行上面的代码。我希望UICollectionView现在显示所有元素，但它不会。

I have a small demo program where I have a data source producing 100 elements. In Interface Builder I initially set the size of the UICollectionView to a small value so that not all elements fit, after that I press a button after which the code above is executed. I expect the UICollectionView to now show all elements, but it doesn't.

编辑：演示程序可以在以下位置找到 https://github.com/mjdemilliano/TestUICollectionView 。

The demo program can be found at https://github.com/mjdemilliano/TestUICollectionView.

EDIT2：我观察到帧更新在某些时候丢失，因为如果我再次按下按钮，当前帧将恢复为旧值。在按钮事件处理程序中添加一些日志语句后，日志输出为：

I have observed that the frame update is lost at some point, because if I press the button again, the current frame is back to the old value. After adding some log statements in the button event handler, the log output is:

before: frame = {{0, 58}, {320, 331}}, contentSize = {320, 1190}
update button pressed
after: frame = {{0, 0}, {300, 2000}}, contentSize = {300, 2000}
before: frame = {{0, 58}, {320, 331}}, contentSize = {320, 1190}
update button pressed
after: frame = {{0, 0}, {300, 2000}}, contentSize = {300, 2000}

我不明白为什么不保留帧更改，更改它的是什么。

在某些时候我会用值替换硬编码值从流程布局中获得，但我想排除这一点，并尽可能简单地保持我的例子。

At some point I will replace the hardcoded values by values obtained from the flow layout, but I wanted to rule that out and keep my example as simple as possible.

背景：我最终想要做的是：具有可滚动的视图，其中包含标签和图像等各种控件，以及具有动态内容的集合视图。我想滚动所有这些，而不仅仅是集合视图，因此我没有使用集合视图自己的滚动工具，它工作正常。

Context: What I want to do eventually is the following: I have a scrollable view with various controls like labels and images, and a collection view with dynamic content. I want to scroll all that, not just the collection view, therefore I am not using the collection view's own scrolling facilities, which work fine.

推荐答案

我最终通过修复所有自动布局问题，使用约束修复集合视图的高度来解决这个问题。然后，每当我知道内容已更改时，我使用值 collectionView.contentSize.height 更新约束的值：

I solved this eventually by fixing all Auto Layout issues, fixing the height of the collection view using a constraint. Then, whenever I know the content has changed I update the value of the constraint using the value collectionView.contentSize.height:

self.verticalLayoutConstraint.constant = self.collectionView.contentSize.height;

然后正确调整集合视图的大小，它在整个scrollview中表现良好。我用我的更改更新了GitHub测试项目。

Then the collection view is resized properly and it behaves nicely within the overall scrollview. I have updated the GitHub test project with my changes.

对我来说，通过手动更新约束而不是告诉iOS来做到这一点：制作集合视图的框架高度尽可能大对我来说感觉不对，但它是迄今为止我提出的最好的。如果你有一个答案，请发一个更好的答案。

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