Objective-c的collectionview不加载数据

Question

不知何故我的collectionView不加载我的数据。我从facebook获取数据，并在数组填充后调用reloadData，但没有发生任何事情…

没有Cell的显示，因为当ViewDidLoad被调用时数组是0。

我如何重新加载，它对collectionView生效?我的代码有什么问题?

CollectionViewController.h

#import <UIKit/UIKit.h>
#import <FacebookSDK/FacebookSDK.h>
@interface CollectionViewController : UICollectionViewController <UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>
@property (nonatomic, weak) IBOutlet UICollectionView *collectionView;
@property (nonatomic, strong) NSMutableArray *searches;
- (IBAction)getFotos:(id)sender; 
@end

CollectionViewController.m

#import "CollectionViewController.h"
#import "CollectionViewCell.h"
#import "BHPhoto.h"
@interface CollectionViewController () 
@end
@implementation CollectionViewController
@synthesize collectionView;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    NSMutableArray *searches = [[NSMutableArray alloc] init];
    self.searches = searches;
    [self getFotos:nil];
    NSLog(@"searches amount: %u", [self.searches count]);
    [self.collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"collcell"];
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
#pragma mark - UICollectionView Datasource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    int ret = [self.searches count];   // <-- here the searches return 0 instead of the filled searches size, what I though will happen if reloadData is called
    NSLog(@"numberOfItemsinSection - I: %d", ret); 
    return ret;
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    int ret = 1;
    NSLog(@"numberOfSection - S: %d", ret);
    return ret;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [cv dequeueReusableCellWithReuseIdentifier:@"collcell" forIndexPath:indexPath];
    cell.backgroundColor = [UIColor whiteColor];
    return cell; 
}
#pragma mark - UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    // @todo select
}
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
    // @todo de-select
}
#pragma mark - UICollectionViewDelegateFlowLayout
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"SETTING SIZE FOR ITEM AT INDEX %d", indexPath.row);
    return CGSizeMake(80, 80);
}
#pragma mark -
#pragma mark get Facebook fotos around me
- (IBAction)getFotos:(id)sender {
    NSLog(@"getFotos in collview");
    [FBRequestConnection
     startWithGraphPath:@"search?type=place&center=43.119340,22.694992&distance=1000&fields=picture"
     completionHandler:^(FBRequestConnection *connection,
                         id result,
                         NSError *error) {
         if (!error) {
              [self readjson:result];
         }
     }];
}
#pragma mark read json for search location
- (IBAction)readjson:(NSDictionary *)jsondata {
    NSLog(@"keys: %@", [jsondata allKeys]);
    for (id item in [jsondata objectForKey:@"data"]) {        
        // add Photos to array
        NSURL *photoURL = item[@"picture"][@"data"][@"url"]; 
        BHPhoto *photo = [BHPhoto photoWithImageURL:photoURL];
        [self.searches addObject:photo];
    }
    NSLog(@"searches content: %@", self.searches);
    [self.collectionView reloadData]; // <-- reload data is called but does not have an effect...
}

@end

调试输出:

2013-01-11 00:23:46.308 foobar[3099:19a03] getFotos in collview
2013-01-11 00:23:46.309 foobar[3099:19a03] searches amount: 0
2013-01-11 00:23:46.312 foobar[3099:19a03] numberOfSection - S: 1
2013-01-11 00:23:46.312 foobar[3099:19a03] numberOfItemsinSection - I: 0
2013-01-11 00:23:46.591 foobar[3099:19a03] keys: (
    data,
    paging
)
2013-01-11 00:23:46.592 foobar[3099:19a03] searches content: (
    "<BHPhoto: 0x9351460>",
    "<BHPhoto: 0x938ad20>",
    "<BHPhoto: 0x938ade0>",
    "<BHPhoto: 0x938ae90>",
    "<BHPhoto: 0x938af40>",
    "<BHPhoto: 0x938b000>"
)

欢呼

Answer 1

您忘记将类设置为它自己的委托/数据源。在你的控制器类init中，像这样添加这些行，这样它就知道你的协议实现是为它自己的:

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.collectionview.delegate = self;
        self.collectionview.datasource = self;
    }
    return self;
}

这花了我一段时间，但我注意到你的调试输出只调用numberOfItemsInSection:一次(在viewDidLoad)。当你调用[self。collectionview reloadData]，它将再次调用该方法，所以你应该看到另一个具有正确计数的调试消息。