ios - Collection View :cellForItemAtIndexPath: never gets called

Question

我有一个 UICollectionView，我只是想让它显示出来。我在界面生成器中将委托(delegate)和数据源附加到文件的所有者。

collectionView:numberOfItemsInSection:

被调用就好了。

我已经搞砸了几个小时，就是想不通......

任何帮助都会很棒，提前致谢!

这是完整的源代码。对不起，如果它有点乱。

.h文件

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#import "PinAnnotation.h"

#import "Jot.h"

@interface JotCardViewController : UIViewController <MKMapViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>

@property (nonatomic,strong) Jot* jot;

@end

.m文件

#import "JotCardViewController.h"

#import "JotViewController.h"

#import <QuartzCore/QuartzCore.h>

@interface JotCardViewController ()

@property (nonatomic,strong) JotViewController *detailViewController;
@property (nonatomic,strong) IBOutlet UIView *cardFrontView;
@property (nonatomic,assign,getter = isFlipped) BOOL flipped;
@property (nonatomic,weak) IBOutlet MKMapView *mapView;
@property (nonatomic,strong) IBOutlet UICollectionView *collectionView;

@property (nonatomic,weak) IBOutlet UILabel *jotTitle;
@property (nonatomic,weak) IBOutlet UILabel *jotDate;
@property (nonatomic,weak) IBOutlet UILabel *sunriseSunsetDelta;
@property (nonatomic,weak) IBOutlet UILabel *jotNotes;

@end

@implementation JotCardViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    [[self mapView] setRegion:MKCoordinateRegionMakeWithDistance(CLLocationCoordinate2DMake([self.jot.latitude floatValue], [self.jot.longitude floatValue]), 1000, 1000)];
    //TODO: if there is no jot location - say that their isn't (maybe text over the map display)
    CLLocation *tempLocation = [[CLLocation alloc] initWithCoordinate:CLLocationCoordinate2DMake([self.jot.latitude doubleValue], [self.jot.longitude doubleValue]) altitude:0 horizontalAccuracy:0 verticalAccuracy:0 timestamp:nil];
    [self dropPin:tempLocation];


    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];


    [self.collectionView reloadData];
}

- (void) viewWillAppear:(BOOL)animated
{
    [self refreshUIFromJot];
}

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

- (IBAction)flipToDetails:(id)sender
{
    if (![self isFlipped]) {
        if (!self.detailViewController) {
            JotViewController *jotViewController = [[JotViewController alloc] initWithNibName:@"JotView" bundle:[NSBundle mainBundle]];
            jotViewController.jot = self.jot;
            self.detailViewController = jotViewController;
            self.detailViewController.view.frame = self.cardFrontView.frame;
            self.detailViewController.view.layer.cornerRadius = 10.0;
        }

        [UIView transitionFromView:self.cardFrontView toView:self.detailViewController.view duration:0.33 options:UIViewAnimationOptionCurveLinear |UIViewAnimationOptionTransitionFlipFromRight completion:^(BOOL finished) {
            [self setFlipped:YES];
        }];
    } else {
        [UIView transitionFromView:self.detailViewController.view toView:self.cardFrontView duration:0.33 options:UIViewAnimationOptionCurveLinear |UIViewAnimationOptionTransitionFlipFromLeft completion:^(BOOL finished) {
            [self setFlipped:NO];
        }];
    }
}

- (void) setJot:(Jot *) jot {
    _jot = jot;
    [self refreshUIFromJot];
}

- (void) refreshUIFromJot
{
    [[self jotTitle] setText:self.jot.summary];
    [[self jotDate] setText:self.jot.recorddate];
    [[self jotNotes] setText:self.jot.note];
    [[self sunriseSunsetDelta] setText:@""];
}

-(void) dropPin: (CLLocation*)newLocation{

    for (id<MKAnnotation> pin in self.mapView.annotations){
        MKAnnotationView* anView = [self.mapView viewForAnnotation: pin];
        if (anView){
            [self.mapView removeAnnotation:pin];
            NSLog(@"Pin removed");
        }
    }

    PinAnnotation *pin = [[PinAnnotation alloc] initWithCoordinates:newLocation.coordinate placeName:nil description:nil];
    [self.mapView addAnnotation:pin];


}

#pragma  mark - MKMapViewDelegate methods

- (void) mapViewDidFinishLoadingMap:(MKMapView *)mapView
{
    NSLog(@"Map!");
}

#pragma mark - UICollectionView DataSource

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
    return 1;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    //cell.backgroundColor = [UIColor colorWithPatternImage:[self.results objectAtIndex:indexPath.row]];
    return cell;

    //###
    /*
    NSSet *jotImages = self.jot.images;
    NSSortDescriptor *imageNameDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"imageName" ascending:YES];
    NSArray *sortedJotImages = [jotImages sortedArrayUsingDescriptors:@[imageNameDescriptor]];
    */
    //###
}


#pragma mark - UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    // TODO: Select Item
}
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {
    // TODO: Deselect item
}

#pragma mark – UICollectionViewDelegateFlowLayout

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CGSize retval = CGSizeMake(100, 100);
    return retval;
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(50, 20, 50, 20);
}

@end

Answer 1

我遇到了类似的问题。 cellForItemAtIndexPath 未被调用。拔头发几分钟后，我从 viewDidLoad 方法中删除了 collectionView registerClass:forCellWithReuseIdentifier。

之后，cellForItemAtIndexPath 开始被调用。

希望对您有所帮助。