UIRefreshControl on UICollectionView only works if

问题:

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.

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

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);
}

回答1:

Try this:

self.collectionView.alwaysBounceVertical = YES;

Complete code for a 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;

回答2:

Attributes/Scroll View/Bounce Vertically in Storyboard/Xib

回答3:

Larry's answer in swift:

    let refreshControl = UIRefreshControl()
    refreshControl.tintColor = UIColor.blueColor()
    refreshControl.addTarget(self, action: "refresh", forControlEvents: .ValueChanged)
    collectionView.addSubview(refreshControl)
    collectionView.alwaysBounceVertical = true

Swift 3:

    let refreshControl = UIRefreshControl()
    refreshControl.tintColor = .blue
    refreshControl.addTarget(self, action: #selector(refresh), for: .valueChanged)
    collectionView.addSubview(refreshControl)
    collectionView.alwaysBounceVertical = true

回答4:

If your collectionview has a content size big enough to scroll vertically, it's OK, but in your case it's not.

You must enable the property AlwaysBounceVertical, so you could set self.collectionView.alwaysBounceVertical = YES;

回答5:

I too was facing the same issue, I was not able to use the UIRefreshControl until the UICollectionView's content size was large enough to scroll vertically,

Setting the bounces property of UICollectionView solved this

[self.collectionView setBounces:YES];
[self.collectionView setAlwaysBounceVertical:YES];