Question

我有一个UICollectionView，它显示了一个json url的数组。

当用户滚动到collectionView的末尾时，我想将另一个json url数组附加到我的collectionView。我是这样做的，但它没有用。例如，collectionView中的项目是36，但在collectionView中，我在页面中间看到其中的6个。我的代码：

- (void)loadMore {

NSString *path = @"https://example.com/?json=get_posts&page=2";

path = [path stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

NSURL *url = [NSURL URLWithString:path];

NSData *data = [NSData dataWithContentsOfURL:url];

NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];

NSArray *array = json[@"posts"];

self.contentArray = [self.contentArray arrayByAddingObjectsFromArray:array];

NSLog(@"%ld",(long)self.contentArray.count);

[self.contentCollection reloadData];

}
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
    NSInteger lastSectionIndex = [self.contentCollection numberOfSections] -1;
    NSInteger lastRowIndex = [self.contentCollection numberOfItemsInSection:lastSectionIndex] -1;
    if ((indexPath.section == lastSectionIndex) && (indexPath.row == lastRowIndex)) {
        [self loadMore];
    }
}

谢谢。

Answer 1

SELECT  id, 
        datum,
        stanjekm,
        tocenolit,
        stanjekm - lag (stanjekm,1,0) over (order by id) as PredjenoKm
FROM Gorivo as

//对于数组使用此addObjectsFromArray

Answer 2

不要重新初始化self.contentArray。

做[self.contentArray addObjectsFromArray:array]; 它会将新对象附加到旧数组。但请确保contentArray是NSMutableArray。

Answer 3

好的我用以下代码解决了这个问题：

在我的ViewController.h中：

@property (assign, nonatomic) int page;
@property (strong, nonatomic) NSArray *contentArray;
@property (strong, nonatomic) IBOutlet UICollectionView *contentCollection;

在我的ViewController.m中：

- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
NSInteger lastSectionIndex = [self.contentCollection numberOfSections] - 1;
NSInteger lastRowIndex = [self.contentCollection numberOfItemsInSection:lastSectionIndex] - 1;
if ((indexPath.section == lastSectionIndex) && (indexPath.item == lastRowIndex)) {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    NSString *path = [NSString stringWithFormat:@"http://example.com/?json=get_posts&page=%d",self.page];

    path = [path stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

    NSURL *url = [NSURL URLWithString:path];

    NSData *data = [NSData dataWithContentsOfURL:url];

    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
    NSArray *array = json[@"posts"];

    self.contentArray = [self.contentArray arrayByAddingObjectsFromArray:array];

    NSLog(@"%ld",(long)self.contentArray.count);
    dispatch_async(dispatch_get_main_queue(), ^ {
    [self.contentCollection reloadData];
        self.page = self.page + 1;
        });
    });
}}

将数组追加到UICollectionView

3 个答案: