TableView跳过一些单元格以显示JSON中的数据

Question

因此，我能够解析JSON数据，但是当我尝试在TableView中显示它时，将显示第一行，然后显示第六行数据，依此类推：

这是我检索数据的方式：

- (void)getData{

    NSURL *url = [NSURL URLWithString:@"https://gist.githubusercontent.com/hart88/198f29ec5114a3ec3460/raw/8dd19a88f9b8d24c23d9960f3300d0c917a4f07c/cake.json"];

    NSData *data = [NSData dataWithContentsOfURL:url];

    NSError *jsonError;
    id responseData = [NSJSONSerialization
                       JSONObjectWithData:data
                       options:kNilOptions
                       error:&jsonError];
    if (!jsonError){
        self.objects = responseData;
        NSLog(@"%@", self.objects);
        [self.tableView reloadData];
    } else {
    }

}

这就是我在cellforRowAt中显示它们的方式：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
CakeCell *cell = (CakeCell*)[tableView dequeueReusableCellWithIdentifier:@"CakeCell"];
[self.tableView registerClass:[CakeCell self] forCellReuseIdentifier:@"CakeCell"];

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
dispatch_async(queue, ^(void) {

    NSDictionary *object = self.objects[indexPath.row];
    cell.titleLabel.text = object[@"title"];
    cell.descriptionLabel.text = object[@"desc"];


    NSURL *aURL = [NSURL URLWithString:object[@"image"]];
    NSData *data = [NSData dataWithContentsOfURL:aURL];
    UIImage *image = [UIImage imageWithData:data];
    [cell.cakeImageView setImage:image];

});

return cell;
}

Answer 1

问题是您从后台线程访问UIKit元素。 您可以通过以下方式对其进行重构。

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    CakeCell *cell = (CakeCell*)[tableView dequeueReusableCellWithIdentifier:@"CakeCell"];
    [self.tableView registerClass:[CakeCell self] forCellReuseIdentifier:@"CakeCell"];

    NSDictionary *object = self.objects[indexPath.row];
    cell.titleLabel.text = object[@"title"];
    cell.descriptionLabel.text = object[@"desc"];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
    dispatch_async(queue, ^(void) {        
        NSURL *aURL = [NSURL URLWithString:object[@"image"]];
        NSData *data = [NSData dataWithContentsOfURL:aURL];
        UIImage *image = [UIImage imageWithData:data];

        dispatch_async(dispatch_get_main_queue(), ^{
            [cell.cakeImageView setImage:image];
        });        
    });    
    return cell;
}

如果由于后台操作而需要更新某些UI，请始终将此代码包装在dispatch_async(dispatch_get_main_queue(), ^{...})调用中