UICollectionView上的UIRefreshControl仅在集合填充容器高度时才有效

问题描述

我正在尝试将 UIRefreshControl 添加到 UICollectionView ，但问题是刷新控件确实除非集合视图填满其父容器的高度，否则不会出现。换句话说，除非集合视图足够长以至于需要滚动，否则无法向下拉以显示刷新控件视图。一旦集合超过其父容器的高度，它就会被拉下并显示刷新视图。

I'm trying to add a UIRefreshControl to a UICollectionView, but the problem is that the refresh control does not appear unless the collection view fills up the height of its parent container. In other words, unless the collection view is long enough to require scrolling, it cannot be pulled down to reveal the refresh control view. As soon as the collection exceeds the height of its parent container, it is pulled down and reveals the refresh view.

我已经设置了一个只有一个 UICollectionView 在主视图中，有一个出口到集合视图，以便我可以在<$中添加 UIRefreshControl C $ C> viewDidLoad中。还有一个原型单元格，其重用标识符 cCell

I have set up a quick iOS project with just a UICollectionView inside the main view, with an outlet to the collection view so that I can add the UIRefreshControlto it in viewDidLoad. There is also a prototype cell with the reuse identifier cCell

这是控制器中的所有代码，它很好地证明了这个问题。在此代码中，我将单元格的高度设置为100，这不足以填充显示，因此无法拉取视图并且不会显示刷新控件。将其设置为更高的值以填充显示，然后它可以工作。有什么想法？

This is all the code in the controller, and it demonstrates the issue pretty well. In this code I set the height of the cell to 100, which isn't enough to fill the display, and therefore the view cannot be pulled and the refresh control won't show. Set it to something higher to fill the display, then it works. Any ideas?

@interface ViewController () <UICollectionViewDelegateFlowLayout, UICollectionViewDataSource>
@property (strong, nonatomic) IBOutlet UICollectionView *collectionView;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
    [self.collectionView addSubview:refreshControl];
}

-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return 1;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    return [collectionView dequeueReusableCellWithReuseIdentifier:@"cCell" forIndexPath:indexPath];
}

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return CGSizeMake(self.view.frame.size.width, 100);
}

推荐答案

试试这个：

self.collectionView.alwaysBounceVertical = YES;

完整代码对于 UIRefreshControl

UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
refreshControl.tintColor = [UIColor grayColor];
[refreshControl addTarget:self action:@selector(refershControlAction) forControlEvents:UIControlEventValueChanged];
[self.collectionView addSubview:refreshControl];
self.collectionView.alwaysBounceVertical = YES;

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