替換不添加：UICollectionView

Question

我正在爲Instagram創建一個客戶端應用程序獲取圖片，但是當用戶到達頁面底部時，它應該帶來一組新的uicollectionviewcell，但是它會替換現有的和我除非我刷新，否則不能再看到它們。所有nessecary代碼提供如下，感謝您的幫助提前：

@interface StreamViewController() <UITextFieldDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout> 
@property (nonatomic, strong) NSMutableDictionary *timelineResponse; 
@property (nonatomic, strong) CredentialStore *credentialStore; 
@property (weak, nonatomic) IBOutlet UICollectionView *collectionView; 

@end 

@implementation StreamViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    [self refreshInstagram]; 

    //Refresh 
    UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init]; 
    [refreshControl addTarget:self action:@selector(startRefresh:) 
      forControlEvents:UIControlEventValueChanged]; 
    [self.collectionView addSubview:refreshControl]; 

    //Instigate Navigation Bar Buttons 
    UIButton *barButton = [UIButton buttonWithType:UIButtonTypeCustom]; 

    [barButton setTitle:@"" forState:UIControlStateNormal]; 
    [barButton setBackgroundImage:[UIImage imageNamed:@"barButton.png"] forState:UIControlStateNormal]; 
    [barButton setBackgroundImage:[UIImage imageNamed:@"barButton_s.png"] forState:UIControlStateHighlighted]; 
    [barButton addTarget:self action:@selector(didTapBarButton:) forControlEvents:UIControlEventTouchUpInside]; 
    barButton.frame = CGRectMake(0.0f, 0.0f, 30.0f, 30.0f); 
    UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithCustomView:barButton]; 

    self.navBar.leftBarButtonItem = barButtonItem; 

    UIButton *postButton = [UIButton buttonWithType:UIButtonTypeCustom]; 

    [postButton setTitle:@"" forState:UIControlStateNormal]; 
    [postButton setBackgroundImage:[UIImage imageNamed:@"pen_usIMG.png"] forState:UIControlStateNormal]; 
    [postButton setBackgroundImage:[UIImage imageNamed:@"pen_sIMG.png"] forState:UIControlStateHighlighted]; 
    [postButton addTarget:self action:@selector(didTapPostButton:) forControlEvents:UIControlEventTouchUpInside]; 
    postButton.frame = CGRectMake(0.0f, 0.0f, 30.0f, 30.0f); 
    UIBarButtonItem *postButtonItem = [[UIBarButtonItem alloc] initWithCustomView:postButton]; 

    self.navBar.rightBarButtonItem = postButtonItem; 

    //Reload by default 
    [self.collectionView reloadData]; 

} 


//Global refresh Instagram Method 
- (void)refreshInstagram { 

    [[InstagramClient sharedClient] getPath:@"users/self/feed" 
           parameters:nil 
            success:^(AFHTTPRequestOperation *operation, id responseObject) { 
             NSLog(@"Response: %@", responseObject); 

             self.timelineResponse = [responseObject mutableCopy]; 
             [self.collectionView reloadData]; 

            } failure:^(AFHTTPRequestOperation *operation, NSError *error) { 
             NSLog(@"Failure: %@", error); 
            }]; 

} 

- (void)nextInstagramPage:(NSIndexPath *)indexPath{ 
    NSDictionary *page = self.timelineResponse[@"pagination"]; 
    NSString *nextPage = page[@"next_url"]; 


    [[InstagramClient sharedClient] getPath:[NSString stringWithFormat:@"%@",nextPage] parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) { 

     self.timelineResponse = [responseObject mutableCopy]; 
     [self.timelineResponse addEntriesFromDictionary:responseObject]; 
     [self.collectionView reloadData]; 

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) { 
     NSLog(@"Failure: %@", error); 
    }]; 



} 
- (NSMutableArray *)entries { 
    return self.timelineResponse[@"data"]; 
} 

- (NSArray *)pages { 
    return self.timelineResponse[@"pagination"]; 
} 


- (NSURL *)imageUrlForEntryAtIndexPath:(NSIndexPath *)indexPath { 
    NSDictionary *entry = [self entries][indexPath.row]; 
    NSString *imageUrlString = entry[@"images"][@"standard_resolution"][@"url"]; 
    return [NSURL URLWithString:imageUrlString]; 
} 

#pragma mark - UICollectionViewDelegate 

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath { 
    //int y = arc4random() % 200+50; 


    return CGSizeMake(150, 150); 


} 
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath 
{ 
    RNBlurModalView *modal = [[RNBlurModalView alloc] initWithViewController:self title:@"Item Tapped!" message:@"Thank God its working"]; 
    [modal show]; 
} 


- (void)scrollViewDidScroll:(UIScrollView *)scrollView 
{ 
    if (scrollView.contentOffset.y == roundf(scrollView.contentSize.height-scrollView.frame.size.height)) { 
     NSLog(@"we are at the endddd"); 
     NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0]; 

     [self nextInstagramPage:indexPath]; 


    } 
} 

#pragma mark - UICollectionViewDataSource 

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { 

    return [[self entries] count]; 

} 

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { 

    ImageCell *cell = (ImageCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"imageCell" 
                      forIndexPath:indexPath]; 
    NSURL *url = [self imageUrlForEntryAtIndexPath:indexPath]; 
    NSLog(@"%@", url); 
    [cell.imageView setImageWithURL:url]; 
    cell.backgroundColor = [UIColor whiteColor]; 

    return cell; 
} 

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

#pragma mark - NavigationBarButtons 

- (void)didTapBarButton:(id)sender { 

    [self.sidePanelController showLeftPanelAnimated:YES]; 

} 

- (void)startRefresh:(UIRefreshControl *)sender { 
    [self refreshInstagram]; 
    [sender endRefreshing]; 

} 

-(void)didTapPostButton:(id)sender { 


} 

@end 

Answer 1

你的問題可能是從該行出現：

self.timelineResponse = [responseObject mutableCopy]; 

在這一點上，在timelineResponse所有對象都將被刪除。嘗試刪除這條線，我敢打賭你會沒事的。