如何使用AFNetworking在UITableCell内部重新加载文本 [英] How to Reload Text Inside UITableCell using AFNetworking

问题描述

我正在从Rotten Tomatoes API中获取我的 UILabel 的值，我希望自定义单元格中的文本只要已经获取该值就可以更新。我尝试通过重新加载我的 UITableView 来做到这一点，但是它循环了。

I'm fetching the value of my UILabel from Rotten Tomatoes API and I want my text inside my custom cell to update whenever the value has been fetched already. I tried doing that by reloading my UITableView but it goes on a loop.

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
    }
}

如果我添加了在我的文本中设置值之后，代码 [self.myTableView reloadData]; 就会循环运行。最好的方法是什么？谢谢！

If I added the code [self.myTableView reloadData]; after setting the value in my text, it goes on a loop. What's the best way to do this? Thanks!

更新：包括更新的代码和另一种方法。另外，我的ratingTomatoLabel在未显示时始终为零。

UPDATE: Included updated code and another method. Also, my ratingTomatoLabel always goes nil when it's not displayed.

推荐答案

您应使用 KVO（键值观察）来检测字典或数组是否发生更改-在这种情况下，似乎是 self.testDict 。

You should use KVO (Key-value observing) to detect when there are changes to your dictionary or array - in this case it seems self.testDict.

收到此通知时，请使用UITableView的 -visibleCells 方法仅更新可见的单元格-当其他单元格使用 -tableView：cellForRowAtIndexPath：。

When you receive this notification, use UITableView's -visibleCells method to update only the visible cells - the others will obviously take on their new value when their cell is recycled using -tableView:cellForRowAtIndexPath:.

KVO需要什么：当视图加载/更改并设置您要观察的变量时注册/注销...

What's required for KVO: Registering/deregistering when views load/change and setting the variable you wish to observe...

- (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：方法可让底层系统刷新单元格。

Lastly, to update the cell(s) that have changed, call the -reloadRowsAtIndexPaths:withRowAnimation: method to have the underlying system refresh the cell.

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