UICollectionViewCell higher y than UICollectionview

Question

I have a UICollectionView in my app, that I initialize with the following code:

UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
layout.itemSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height);
[layout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
self.collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)
                                                     collectionViewLayout:layout];
self.collectionView.backgroundColor = [UIColor clearColor];
self.collectionView.delegate = self;
self.collectionView.dataSource = self;
[self.collectionView setPagingEnabled:YES];
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"normalCell"];
[self.collectionView setShowsHorizontalScrollIndicator:NO];
[self.collectionView setShowsVerticalScrollIndicator:NO];
[self.view addSubview:self.collectionView];

Then I added all the protocol methods:

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

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
    return 0;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionView *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
    return 0;
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 3;
}


- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return 3;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"normalCell" forIndexPath:indexPath];

    if (indexPath.row == 0) {
        cell.backgroundColor = [UIColor blueColor];
    } else if (indexPath.row == 1) {
        cell.backgroundColor = [UIColor greenColor];
    } else if (indexPath.row == 2) {
        cell.backgroundColor = [UIColor yellowColor];
    }

    return cell;
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    UIEdgeInsets safeInsets = self.tabBarController.view.safeAreaInsets;

    NSLog(@"Top: %f", safeInsets.top);

    self.collectionView.frame = CGRectMake(0, safeInsets.top, self.view.frame.size.width, self.view.frame.size.height-safeInsets.top);
    [self.collectionView reloadData];
}

Now, the UICollectionView is placed perfectly within my view. The UICollectionViewCell however, starts much higher than the UICollectionView .

In the screenshot below you can see the behaviour. In blue, you can see the UICollectionViewCell and in yellow, you can see the UICollectionView . As you can see it seems to have a higher y-coordinate then the UICollectionView .

I've been busting my head for a couple of hours now, but I can't seem to figure out why it's doing this. Any ideas?

Answer 1

在这里，您可以根据tabbarcontroller设置单元格高度，以使其高于单元格高度，而只是通过单元格设置高度。