Question

下午好，

我试图在 UITableViewController （CarTableViewController）中显示数据，此时正在使用正确的信息填充行，还有 refreshControl 工作正常（并且非常快，如1秒），但是第一次进入我的应用程序时，数据不显示（我必须用手指移动屏幕，然后显示数据）。（我必须等待+ 15秒直到它自动出现，但有时候没有显示）。

如何自动快速地显示数据？

我尝试将 reloadData 移动到每个方法中，它总是一样的，我不知道还能做什么......！如果你能帮助我，我将不胜感激。

CarTableViewController.m

#import "CarTableViewController.h"
#import "CarTableViewCell.h"
#import "CarTableViewController.h"
#import "CarDetailViewController.h"
#import <SDWebImage/UIImageView+WebCache.h>

@implementation CarTableViewController

@synthesize carMakes = _carMakes;
@synthesize carModels = _carModels;
@synthesize carImages = _carImages;

@synthesize likes = _likes;
@synthesize comments = _comments;
@synthesize username = _username;
@synthesize refuser = _refuser;
@synthesize profileImage = _profileImage;

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self fetchJson];

    [self.tableView reloadData];

    // Initialize the refresh control.
    self.refreshControl = [[UIRefreshControl alloc] init];
    self.refreshControl.backgroundColor = [UIColor blackColor];
    self.refreshControl.tintColor = [UIColor whiteColor];
    [self.refreshControl addTarget:self
                            action:@selector(fetchJson)
                  forControlEvents:UIControlEventValueChanged];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [_jsonArray count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"carTableCell";
    CarTableViewCell *cell = [tableView
                              dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {
        cell = [[CarTableViewCell alloc]
                initWithStyle:UITableViewCellStyleDefault
                reuseIdentifier:CellIdentifier];
    }

    // Configure the cell...
    cell.makeLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"id"];
    cell.likes.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"likes"];
    cell.comments.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"comments"];
    cell.username.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"username"];
    cell.refuser.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"user_ref"];
    cell.modelLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"user"];

    NSURL * imageURL = [NSURL URLWithString:[[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"imagen"]];
    [cell.carImage setImageWithURL:imageURL
                  placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                           options:SDWebImageRefreshCached];
    NSURL * imageURL2 = [NSURL URLWithString:[[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"image"]];

    [cell.profileImage setImageWithURL:imageURL2
                      placeholderImage:[UIImage imageNamed:@"image"]
                            options:SDWebImageRefreshCached];

    return cell;
}

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"ShowCarDetails"])
    {
        CarDetailViewController *detailViewController = [segue destinationViewController];

        NSIndexPath *myIndexPath = [self.tableView indexPathForSelectedRow];

        detailViewController.carDetailModel = [[NSArray alloc]
                                               initWithObjects:
                                               [[_jsonArray objectAtIndex:[myIndexPath row]] valueForKey:@"date"],
                                               [[_jsonArray objectAtIndex:[myIndexPath row]] valueForKey:@"id"],
                                               [[_jsonArray objectAtIndex:[myIndexPath row]] valueForKey:@"imagen"],
                                               nil];
    }
}

-(void)fetchJson {
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{

        NSString * urlString = [NSString stringWithFormat:@"http://mywebsite.com/service.php"];
        NSURL * url = [NSURL URLWithString:urlString];
        NSData * data = [NSData dataWithContentsOfURL:url];

        self.carModels = [[NSMutableArray alloc] init];
        self.carMakes = [[NSMutableArray alloc] init];
        self.carImages = [[NSMutableArray alloc] init];
        self.likes = [[NSMutableArray alloc] init];
        self.comments = [[NSMutableArray alloc] init];

        @try
        {
            NSError *error;
            [_jsonArray removeAllObjects];
            _jsonArray = [NSJSONSerialization
                         JSONObjectWithData:data
                         options:NSJSONReadingMutableContainers|NSJSONReadingMutableLeaves
                         error:&error];

            for(int i=0;i<_jsonArray.count;i++)
            {
                NSDictionary * jsonObject = [_jsonArray objectAtIndex:i];
                NSString* imagen = [jsonObject objectForKey:@"imagen"];
                [_carImages addObject:imagen];

                NSDictionary * jsonObject2 = [_jsonArray objectAtIndex:i];
                NSString* user = [jsonObject2 objectForKey:@"user"];
                [_carMakes addObject:user];

                NSDictionary * jsonObject3 = [_jsonArray objectAtIndex:i];
                NSString* date = [jsonObject3 objectForKey:@"date"];
                [_carModels addObject:date];
            }
        }
        @catch (NSException * e)
        {
            NSLog(@"Exception: %@", e);
        }
        @finally
        {
            [self.tableView reloadData];
            [self.refreshControl endRefreshing];
        }
    }
    );
}

@end

CarTableViewController.h

#import <UIKit/UIKit.h>

@interface CarTableViewController : UITableViewController

@property (nonatomic, strong) IBOutlet UITableView *tableView;

@property (nonatomic, strong) NSMutableArray *carImages;
@property (nonatomic, strong) NSMutableArray *carMakes;
@property (nonatomic, strong) NSMutableArray *carModels;

@property (nonatomic, strong) NSMutableArray *likes;
@property (nonatomic, strong) NSMutableArray *comments;
@property (nonatomic, strong) NSMutableArray *username;
@property (nonatomic, strong) NSMutableArray *refuser;
@property (nonatomic, strong) NSMutableArray *profileImage;

@property (nonatomic, strong) NSMutableArray *jsonArray;

@end

提前致谢。

Answer 1

您的问题出在fetchJson。你在后台线程上调用reloadData，这会产生不可预测的结果。您需要确保在主线程上调用任何UI方法。

使用以下内容替换您的代码：

- (void)fetchJson
{
    self.carModels = [[NSMutableArray alloc] init];
    self.carMakes = [[NSMutableArray alloc] init];
    self.carImages = [[NSMutableArray alloc] init];
    self.likes = [[NSMutableArray alloc] init];
    self.comments = [[NSMutableArray alloc] init];

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

        NSString * urlString = [NSString stringWithFormat:@"http://mywebsite.com/service.php"];
        NSURL * url = [NSURL URLWithString:urlString];
        NSData * data = [NSData dataWithContentsOfURL:url];

        NSError *error;
        _jsonArray = [NSJSONSerialization
                      JSONObjectWithData:data
                      options:NSJSONReadingMutableContainers | NSJSONReadingMutableLeaves
                      error:&error];

        for (NSDictionary * jsonObject in _jsonArray)
        {
            NSString* imagen = [jsonObject objectForKey:@"imagen"];
            [_carImages addObject:imagen];

            NSDictionary * jsonObject2 = [_jsonArray objectAtIndex:i];
            NSString* user = [jsonObject2 objectForKey:@"user"];
            [_carMakes addObject:user];

            NSDictionary * jsonObject3 = [_jsonArray objectAtIndex:i];
            NSString* date = [jsonObject3 objectForKey:@"date"];
            [_carModels addObject:date];
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            [self.tableView reloadData];
            [self.refreshControl endRefreshing];
        });
    );
}

ReloadData在我的TableViewController中不起作用

1 个答案: