Question

我正在从Rotten Tomatoes API中获取UILabel的值，并且我希望我的自定义单元格中的文本在每次获取值时都会更新。我尝试通过重新加载我的UITableView来做到这一点，但它会循环播放。

这是我的代码：

if (ratingTomatoLabel.text == nil)
    {
        NSLog(@"   Nil");

        NSString *stringWithNoSpaces = [movieTitle.text stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
        NSString *rottenTomatoRatingString = [NSString stringWithFormat:@"%@%@%@", @"http://api.rottentomatoes.com/api/public/v1.0/movies.json?apikey=6844abgw34rfjukyyvzbzggz&q=", stringWithNoSpaces, @"&page_limit=1"];
        NSLog(@"   Rotten URL: %@", rottenTomatoRatingString);
        NSURL *rottenUrl = [[NSURL alloc] initWithString:rottenTomatoRatingString];
        NSURLRequest *rottenRequest = [[NSURLRequest alloc] initWithURL:rottenUrl];

        AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:rottenRequest success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
            NSLog(@"      3");
            self.testDict = [JSON objectForKey:@"movies"];
        } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
            NSLog(@"Request Failed with Error: %@, %@", error, error.userInfo);
        }];

        [operation start];

        NSLog(@"   %@", ratingTomatoLabel.text);
        ratingTomatoLabel.text = @"...";
    }
    else if ([ratingTomatoLabel.text isEqualToString:@""])
    {
        NSLog(@"   isEqualToString");
        // Do nothing
    }
    else
    {
        NSLog(@"   else");
    }

    return tableCell;

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSLog(@"      fetched!");

    if ([ratingTomatoLabel.text isEqualToString:@"..."])
    {
        NSLog(@"      2nd nil");
        NSDictionary *dict = [self.testDict valueForKey:@"ratings"];
        self.criticsScoreString = [NSString stringWithFormat:@"%@", [dict valueForKey:@"critics_score"]];
        self.criticsScoreString = [self.criticsScoreString stringByReplacingOccurrencesOfString:@" " withString:@""];
        self.criticsScoreString = [self.criticsScoreString stringByReplacingOccurrencesOfString:@"(" withString:@""];
        self.criticsScoreString = [self.criticsScoreString stringByReplacingOccurrencesOfString:@")" withString:@""];
        self.criticsScoreString = [NSString stringWithFormat:@"%@%@", self.criticsScoreString, @"%"];

        ratingTomatoLabel.text = self.criticsScoreString;
        NSLog(@"      %@", ratingTomatoLabel.text);
    }
    else
    {
        NSLog(@"      2nd not nil");
        NSLog(@"      %@", ratingTomatoLabel.text);
        // Do nothing
    }
}

如果我在设置文本中的值后添加了代码[self.myTableView reloadData];，则会循环播放。最好的方法是什么？谢谢！

更新：包含更新的代码和其他方法。另外，我的ratingTomatoLabel在没有显示时总是为零。

Answer 1

Jaytrix

AFNetworking调用是异步发生的，考虑使用某种通知来告诉主线程（UI）何时完成工作或发生错误。

谢

Answer 2

您应该使用KVO (Key-value observing)来检测字典或数组何时发生更改 - 在这种情况下似乎self.testDict。

当您收到此通知时，请使用UITableView的-visibleCells方法仅更新可见单元格 - 其他人显然会在使用-tableView:cellForRowAtIndexPath:回收其单元格时使用其新值。

KVO需要什么：在视图加载/更改时注册/取消注册并设置您想要观察的变量......

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if([keyPath isEqual:@"testDict"])
    {
        NSLog(@"KVO change: %@", change);
        NSArray *visibleCells = [self.myTableView visibleCells];
        for(UITableViewCell *cell in visibleCells)
        {
            if(/*cell matches the one I'm targeting OR just update regardless*/)
                // assign value to UILabel
        }
    }
}

// Call this from -viewDidLoad
- (void)registerAsObserver
{
    [self addObserver:self forKeyPath:@"testDict" options:NSKeyValueObservingOptionNew context:NULL];
}

// Call this from -viewWillDisappear and -viewDidUnload (may not be necessary for -viewDidUnload if already implemented in -viewWillDisappear)
- (void)unregisterAsObserver
{
    [self removeObserver:self forKeyPath:@"testDict"];
}

最后，要更新已更改的单元格，请调用-reloadRowsAtIndexPaths:withRowAnimation:方法让底层系统刷新单元格。

如何使用AFNetworking在UITableCell内重新加载文本

2 个答案: