ios - UICollectionView 重新加载数据无法更新 CollectionView

Question

更新:

我确实忘记提到 CollectionView 在 Split View Controller 的右侧，而在左侧，我有 tableView。选择一行后，我传递一个新的 FEED ADDRESS 并让它在右侧运行 refreshFeed 方法。

我有一个从 XML 解析数据的 Collection View 。当按下某个按钮时，我希望它清除 CollectionView，并从不同的 XML 加载数据，这两者都位于在线位置。我使用 ASIHTTPRequest 和 GDATAXML 类来帮助我实现这一目标。这是我的代码。我可以通过日志验证 NSMutableArray 是否已清除，并成功填充了不同的 XML，但 reloadData 永远不会发生，因为 cellForItem 不会被第二次调用。我哪里搞砸了？

@interface RightViewController ()
@property (nonatomic, strong) IBOutlet UICollectionView *collectionView;

@end

@implementation RightViewController

@synthesize allEntries = _allEntries;
@synthesize feeds = _feeds;
@synthesize queue = _queue;
@synthesize webViewController = _webViewController;
@synthesize activity;
@synthesize webViewController2 = _webViewController2;



@synthesize nameit2;
@synthesize nowplaying;
@synthesize entryofmp3 = _entryofmp3;
@synthesize nameit;
@synthesize progress;
@synthesize lastSelection;
@synthesize backgroundTaskIdentifier, theurl;
@synthesize thetable, thepath, downloadlabel, receivedData, progressbutton;


-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return [_allEntries count];
}
- (void)loadFirstTime {
       self.allEntries = [NSMutableArray array];

        self.queue = [[NSOperationQueue alloc] init];


    if (_feedAddress == nil) {
        _feedAddress = @"http://www.316apps.com/AIMAPPLETV/AIMSeries.xml";
    }
    self.feeds = [NSArray arrayWithObjects:_feedAddress,
                  nil];
    for (NSString *feed in _feeds) {
        NSLog(@"Running Fine");
        NSURL *url = [NSURL URLWithString:feed];
        ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
        [request setDelegate:self];
        [_queue addOperation:request];
    }
    NSLog(@"Still Good");
    //[self.collectionView reloadData];


}
-(void)changeFeed {
    [_allEntries removeAllObjects];
    _feedAddress = @"http://www.316apps.com/AIMAPPLETV/AIMCON.xml";
    [self loadFirstTime];
   // self.queue = nil;
    //_request.delegate = nil;
 //   _request.delegate = nil;

  //  [_collectionView reloadData];
}
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
  // [self performSegueWithIdentifier:@"playMovies" sender:self];
     RSSEntry *entry = [_allEntries objectAtIndex:indexPath.row];
    NSString *wifiStreamAddress = entry.articleUrl;
    AVPlayer *player = [[AVPlayer alloc] initWithURL: [NSURL URLWithString: wifiStreamAddress] ];
    AVPlayerViewController *playerViewController = [[AVPlayerViewController alloc] init];
    playerViewController.player = player;

    // Keep pointers to player and controller
    self.player = player;
    self.playerViewController = playerViewController;



    [self presentViewController: playerViewController animated: true completion: ^{
        [self.player play];
    }];


}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Make sure your segue name in storyboard is the same as this line
    if ([[segue identifier] isEqualToString:@"playMovies"])
    {
        PlayMovies *userViewController = [segue destinationViewController];

        //if you need to pass data to the next controller do it here
    }
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {


    RSSEntry *entry = [_allEntries objectAtIndex:indexPath.row];

    static NSString *cellIdentifier = @"cvCell";

    CVCell *cell = (CVCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

        [cell.theimage setImageWithURL:[NSURL URLWithString:entry.articleImage] placeholderImage:[UIImage imageNamed:@"icon@2x.png"]];

    cell.theimage.adjustsImageWhenAncestorFocused = YES;
    cell.theimage.clipsToBounds = false;




    return cell;
}

- (void)viewDidLoad {
        [super viewDidLoad];

    self.allEntries = [NSMutableArray array];
    self.queue = [[NSOperationQueue alloc] init];
        [self loadFirstTime];

}
-(void) viewWillAppear:(BOOL)animated {

}

- (void)parseRss:(GDataXMLElement *)rootElement entries:(NSMutableArray *)entries {

    NSArray *channels = [rootElement elementsForName:@"channel"];
    for (GDataXMLElement *channel in channels) {

        NSString *blogTitle = [channel valueForChild:@"title"];

        NSArray *items = [channel elementsForName:@"item"];
        for (GDataXMLElement *item in items) {
            NSString *articleTitle = [item valueForChild:@"title"];
            NSString *articleUrl = [[[[item elementsForName: @"enclosure"] lastObject] attributeForName: @"url"] stringValue];
            NSString *articleDateString = [item valueForChild:@"pubDate"];
            NSString *picture = [[[[item elementsForName: @"itunes:image"] lastObject] attributeForName: @"href"] stringValue];
            NSDate *articleDate = [NSDate dateFromInternetDateTimeString:articleDateString formatHint:DateFormatHintRFC822];
            RSSEntry *entry = [[RSSEntry alloc] initWithBlogTitle:blogTitle
                                                      articleTitle:articleTitle
                                                        articleUrl:articleUrl
                                                       articleDate:articleDate
                                                      articleImage:picture];


            [entries addObject:entry];
            NSLog(@"%@", entries);
        }
    }
     [self.collectionView reloadData];
}

- (void)parseFeed:(GDataXMLElement *)rootElement entries:(NSMutableArray *)entries {

    if ([rootElement.name compare:@"rss"] == NSOrderedSame) {
        [self parseRss:rootElement entries:entries];
    } else if ([rootElement.name compare:@"feed"] == NSOrderedSame) {
       // [self parseAtom:rootElement entries:entries];
    } else {
        NSLog(@"Unsupported root element: %@", rootElement.name);
    }
}

- (void)requestFinished:(ASIHTTPRequest *)request {
    NSLog(@"Request Finished");
    [_queue addOperationWithBlock:^{

        NSError *error;
        GDataXMLDocument *doc = [[GDataXMLDocument alloc] initWithData:[request responseData]
                                                               options:0 error:&error];
        if (doc == nil) {
            NSLog(@"Failed to parse %@", request.url);
        } else {

            NSMutableArray *entries = [NSMutableArray array];
            [self parseFeed:doc.rootElement entries:entries];

            [[NSOperationQueue mainQueue] addOperationWithBlock:^{

                for (RSSEntry *entry in entries) {

                    int insertIdx = [_allEntries indexForInsertingObject:entry sortedUsingBlock:^(id a, id b) {
                        RSSEntry *entry1 = (RSSEntry *) a;
                        RSSEntry *entry2 = (RSSEntry *) b;
                        return [entry1.articleDate compare:entry2.articleDate];
                    }];
                                       [_allEntries insertObject:entry atIndex:insertIdx];


                }

            }];

        }
    }];

}

- (void)requestFailed:(ASIHTTPRequest *)request {
    NSError *error = [request error];
    NSLog(@"Error: %@", error);
    [self loadFirstTime];
}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

第二次更新:

我正在慢慢到达某个地方。认为这是因为我没有设置 Segue。我从左侧 TableView 的 Cell 到 Collection View 的 View Controller 设置一个 segue 并设置为 ShowDetail，并命名它。然后在 LeftViewController 中:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == 1) {
        [self performSegueWithIdentifier:@"doingIt" sender:self];

    }
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Make sure your segue name in storyboard is the same as this line
    if ([[segue identifier] isEqualToString:@"doingIt"])
    {

        self.rightViewController = [[RightViewController alloc] init];
                [self.rightViewController refresheyc];

        //if you need to pass data to the next controller do it here
    }
}

在 RightViewController 中我有:

-(void)refresheyc {
    NSLog(@"This Sucks");
    [self.allEntries removeAllObjects];
    [self.collectionView reloadData];
    self.allEntries = nil;
    self.queue = nil;
    self.allEntries = [NSMutableArray array];

    self.queue = [[NSOperationQueue alloc] init];




    self.feeds = [NSArray arrayWithObjects:@"http://www.316apps.com/AIMAPPLETV/AIMCON.xml",
                  nil];
    for (NSString *feed in _feeds) {
        NSURL *url = [NSURL URLWithString:feed];
        NSLog(@"URL%@", url);
        ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
        [request setDelegate:self];
        [_queue addOperation:request];
    }

}

CollectionView 中的 Cells 立即消失，但几秒钟后，它们都以相同的方式返回，根本没有改变 XML，但我明白了:

2016-01-09 14:37:31.542 AIM-TV[7965:522091] This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.  This will cause an exception in a future release.
 Stack:(
    0   CoreFoundation                      0x0000000109fa6ff5 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010d45cdeb objc_exception_throw + 48
    2   CoreFoundation                      0x0000000109fa6f2d +[NSException raise:format:] + 205
    3   Foundation                          0x000000010aa96341 _AssertAutolayoutOnMainThreadOnly + 79
    4   Foundation                          0x000000010a8f6d6e -[NSISEngine withBehaviors:performModifications:] + 31
    5   UIKit                               0x000000010c804eb8 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 58
    6   UIKit                               0x000000010c804854 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 646
    7   UIKit                               0x000000010c804ec1 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 67
    8   UIKit                               0x000000010c804589 -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 242
    9   UIKit                               0x000000010c80405d -[UIView(AdditionalLayoutSupport) _initializeHostedLayoutEngine] + 649
    10  UIKit                               0x000000010c7f652a -[UIView(UIConstraintBasedLayout) _initializeLayoutEngine] + 152
    11  UIKit                               0x000000010c7f652a -[UIView(UIConstraintBasedLayout) _initializeLayoutEngine] + 152
    12  UIKit                               0x000000010c804e24 -[UIView(AdditionalLayoutSupport) _layoutEngineCreateIfNecessary] + 62
    13  UIKit                               0x000000010c7f732b -[UIView(UIConstraintBasedLayout) _tryToAddConstraint:roundingAdjustment:mutuallyExclusiveConstraints:] + 126
    14  UIKit                               0x000000010c7f75ef -[UIView(UIConstraintBasedLayout) _addConstraint:] + 274
    15  UIKit                               0x000000010c7fd247 -[UIView(UIConstraintBasedLayout) _updateContentSizeConstraints] + 779
    16  UIKit                               0x000000010c806270 -[UIView(AdditionalLayoutSupport) updateConstraints] + 224
    17  UIKit                               0x000000010c80559b -[UIView(AdditionalLayoutSupport) _internalUpdateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 550
    18  UIKit                               0x000000010c805866 -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 198
    19  UIKit                               0x000000010c8054aa -[UIView(AdditionalLayoutSupport) _internalUpdateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 309
    20  UIKit                               0x000000010c805866 -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 198
    21  UIKit                               0x000000010c8054aa -[UIView(AdditionalLayoutSupport) _internalUpdateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 309
    22  UIKit                               0x000000010c804ec1 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 67
    23  UIKit                               0x000000010c80583a -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededAccumulatingViewsNeedingSecondPassAndViewsNeedingBaselineUpdate:forSecondPass:] + 154
    24  UIKit                               0x000000010c805e9e __60-[UIView(AdditionalLayoutSupport) updateConstraintsIfNeeded]_block_invoke + 98
    25  UIKit

Answer 1

问题真的很奇怪，但它对我有用，我在动画 block 中添加了更新约束代码，

UIView.animate(withDuration: 0.5, animations: {() -> Void in

    //update constraints here

    self.view.layoutIfNeeded() 
    self.collectionView.layoutIfNeeded()

})

self.collectionView.reloadData()