UICollectionView 不会在屏幕旋转时更新其布局

Question

我有一个自定义的UIView 和一个UICollectionView。

在屏幕旋转时，我试图让UICollectionView 在屏幕上伸展，然后重绘其单元格。

下载数据后，我尝试了[grid setNeedsLayout] 和[grid setNeedsDisplay]，但都没有成功。

这就是我想要发生的事情：

肖像

风景

（这也是应用以横向启动时的显示方式，但如果您更改为纵向，它不会更新。）

但是如果我从Portrait 模式开始并切换到Landscape，这就是我得到的。

我正在以编程方式创建这些视图。我没有使用任何情节提要。

我试过了：

-(void)viewDidLayoutSubviews {
    grid = [[MyThumbnailGridView alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height/2, self.view.frame.size.width, self.view.frame.size.height/2)];

}

我也试过玩弄：

- (void) viewWillLayoutSubviews {

    UIInterfaceOrientation interfaceOrientation = [[UIApplication sharedApplication] statusBarOrientation];

    if (UIInterfaceOrientationIsLandscape(interfaceOrientation))
    {
        //LANDSCAPE
        if(grid){
            NSLog(@"Grid Needs Landscape Layout");
            grid.frame =CGRectMake(0, self.view.frame.size.height/2, self.view.frame.size.width, self.view.frame.size.height/2);
            [grid refreshData];
        }

    }else {
        //PORTRIAT
        if(grid){
            NSLog(@"Grid Needs Portrait Layout");
            grid.frame =CGRectMake(0, self.view.frame.size.height/2, self.view.frame.size.width, self.view.frame.size.height/2);
            [grid refreshData];
        }
    }
}

但我无法拉伸。

有什么帮助吗？

MyThumbnailGridView

@interface ViewController () <UINavigationControllerDelegate> {

    MyThumbnailGridView *grid;

    NSMutableArray * arrImages;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    arrImages = [NSMutableArray new];

    grid = [[MyThumbnailGridView alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height/2, self.view.frame.size.width, self.view.frame.size.height/2)];
    //grid = [[MyThumbnailGridView alloc] initWithFrame:CGRectZero];
    NSLog(@"showThumbnailGrid Grid View Size: %@", NSStringFromCGRect(grid.frame));

    [self.view addSubview:grid];

    [self getListOfImages];
}


-(void) getListOfImages {
        //Do background task to get images  and fill arrImages
         [self onDownloadImageDataComplete];    
}


- (void) onDownloadImageDataComplete{
    grid.imageDataSource = arrImages;
    //  [grid setNeedsLayout];
    //  [grid setNeedsDisplay];
}

//...
@end

*MyThumbnailGridView.h

@interface MyThumbnailGridView : UIView

-(id)initWithFrame:(CGRect)frame;
-(void) refreshData;

@property (nonatomic,strong) NSArray *imageDataSource;

@end

*MyThumbnailGridView.m

@interface MyThumbnailGridView () <UICollectionViewDelegate, UICollectionViewDataSource>{
    UICollectionView *collectionView;
}

@end

@implementation MyThumbnailGridView


- (instancetype) initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if(self){
        [self customInit];

    }
    return self;
}
- (void) customInit {
    collectionView = [[UICollectionView alloc] initWithFrame:self.bounds collectionViewLayout:[[MyFlowLayout alloc] init]];
    collectionView.delegate = self;
    collectionView.dataSource = self;
    collectionView.allowsMultipleSelection = NO;
    collectionView.showsVerticalScrollIndicator = YES;
    [collectionView setBackgroundColor:[UIColor darkGrayColor]];
    [collectionView registerClass:[MyCollectionViewCell class] forCellWithReuseIdentifier:@"MyId"];
    [self addSubview:collectionView];
}
- (void) refreshData {
    NSLog(@"Refresh Grid Data");
    [collectionView reloadData];
}

////other code
@end

MyFlowLayout

@interface MyFlowLayout : UICollectionViewFlowLayout
@end

@implementation MyFlowLayout
- (instancetype)init{
    self = [super init];
    if (self)
    {
        self.minimumLineSpacing = 1.0;
        self.minimumInteritemSpacing = 1.0;
        self.scrollDirection = UICollectionViewScrollDirectionVertical;

    }
    return self;
}

- (CGSize)itemSize {
    NSInteger numberOfColumns = 3;
    CGFloat itemWidth = (CGRectGetWidth(self.collectionView.frame) - (numberOfColumns - 1)) / numberOfColumns;
    return CGSizeMake(itemWidth, itemWidth);
}

@end

MyCollectionViewCell

@interface MyCollectionViewCell : UICollectionViewCell
@property (strong, nonatomic)  UIImageView *imageView;
@end
@implementation MyCollectionViewCell

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {

        self.imageView = [UIImageView new];
        [self.imageView setContentMode:UIViewContentModeScaleAspectFill];
        [self.imageView setClipsToBounds:YES];
        [self.imageView setBackgroundColor:[UIColor darkGrayColor]];
        [self.contentView addSubview:self.imageView];

    }
    return self;
}

- (void)prepareForReuse {
    [super prepareForReuse];
    self.imageView.image = nil;
    [self.imageView setHidden:NO];
}

- (void)layoutSubviews {
    [super layoutSubviews];
    [self.imageView setFrame:self.contentView.bounds];
}
@end

Answer 1

这可以解决 您可以在方向的委托函数中更改MyThumbnailGridView 视图的框架，或者使用这样的约束创建视图

(void)viewDidLoad {

   [super viewDidLoad];

    arrImages = [NSMutableArray new];

    grid = [[MyThumbnailGridView alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height/2, self.view.frame.size.width, self.view.frame.size.height/2)];

    [self.view addSubview:grid];    

    [self getListOfImages];

 }

-(void)viewDidLayoutSubviews
{  
   if(Once){

        Once = NO;

       // adding constraints

  MyThumbnailGridView.translatesAutoresizingMaskIntoConstraints = NO;

  [self.MyThumbnailGridView.widthAnchor constraintEqualToConstant:self.view.frame.size.width].active = YES;

  [self.MyThumbnailGridView.heightAnchor constraintEqualToConstant:self.view.frame.size.height/2].active = YES;

  [self.MyThumbnailGridView.leadingAnchor constraintEqualToAnchor:self.view.leadingAnchor].active = YES;

  [self.MyThumbnailGridView.topAnchor  constraintEqualToAnchor:self.view.topAnchor constant:self.view.frame.size.height/2].active = YES;



    }
}

也实现这个

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
    [self.view layoutIfNeeded];
    [MyThumbnailGridView.collectionView invalidate];
// Do view manipulation here.
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
}

Answer 2

问题在于，当应用旋转时，集合视图本身并没有改变大小。你已经给集合视图一个固定的frame，然后就走开了。所以它永远不会改变。所以永远不要再摆出自己的样子。

您应该将 MyThumbnailGridView 及其集合视图子视图 autolayout 约束 赋予它们的父视图，以便它们在应用旋转时正确更改大小。