我正在创建一个应用程序，它从服务器获取 JSON 文本并将其转换为机器人锦标赛的比赛时间表。我有自定义单元格，其中填充了我从网站收到的数据，它们显示每个匹配项的数据都很好。问题是，当我将匹配项放入 .plist 文件(“data.plist”)中时，一旦最初建立了互联网连接，用户不一定需要在应用程序被终止后重新连接到互联网查看当天的比赛时间表。在我不连接到 Internet 之前，我的代码可以完美运行。出于某种原因，一旦互联网连接失败，该应用程序永远不会进入创建单元格的功能。请帮忙!!这是我的代码:

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.

        aRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://jrl.teamdriven.us/source/scripts/getElimMatchResultsJSON.php"] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15.0];
        aConnection = [[NSURLConnection alloc] initWithRequest:aRequest delegate:self];
        if(aConnection){
            receivedData = [NSMutableData data];
        }
        else{
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No Connection!!" message:nil delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

            [alert show];
        }

        paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        jrlDirectory = [paths objectAtIndex:0];
        path = [jrlDirectory stringByAppendingPathComponent:@"data.plist"];

        if (![[NSFileManager defaultManager] fileExistsAtPath:@"data.plist"]) {
            [[NSFileManager defaultManager] copyItemAtPath:[[NSBundle mainBundle]pathForResource:@"data" ofType:@"plist"] toPath:path error:nil];
        }

        dataDict = [[NSMutableDictionary alloc] initWithContentsOfFile:path];    
    }

    - (void)didReceiveMemoryWarning
    {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }



    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
        // Prevents data from repeating itself

        [receivedData setLength:0];
    }

    - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
        [receivedData appendData: data];
    }

    - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Connection Failed" message:nil delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

        [alert show];
        NSLog(@"Connection failed! Error - %@ %@", [error localizedDescription], [[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
    }

    -(void)connectionDidFinishLoading:(NSURLConnection *)connection{

        NSLog(@"Success! Received %d bits of data", [receivedData length]);

        // Must allocate and initialize all mutable arrays before changing them

        sweet16 = [[NSMutableArray alloc]init];
        quarterfinals = [[NSMutableArray alloc]init];
        semi = [[NSMutableArray alloc]init];
        finals = [[NSMutableArray alloc]init];
        dict = [[NSMutableDictionary alloc]init];

        // The error is created and can be referred to if the code screws up (example in the "if(dict)" loop)

        NSError *error;
        dict = [NSJSONSerialization JSONObjectWithData:receivedData options:NSJSONReadingMutableLeaves error:&error];
        matchNames = [[dict objectForKey:@"ElimMatchListResults"]allKeys];
        matchNames = [matchNames sortedArrayUsingSelector:@selector(compare:)];

        // Categorize the matches based on the first two letters of their match names

        for (NSString *name in matchNames) {
            if([[name substringToIndex:2]isEqual:@"16"]){
                 [sweet16 insertObject:[[dict objectForKey:@"ElimMatchListResults"] objectForKey:name] atIndex:sweet16.count];
            }
            else if([[name substringToIndex:2]isEqual:@"Q."]){
                 [quarterfinals insertObject:[[dict objectForKey:@"ElimMatchListResults"]objectForKey:name] atIndex:quarterfinals.count];
            }
            else if([[name substringToIndex:2]isEqual:@"S."]){
                [semi insertObject:[[dict objectForKey:@"ElimMatchListResults"]objectForKey:name] atIndex:semi.count];
            }
            else if([[name substringToIndex:2]isEqual:@"F."]){
                [finals insertObject:[[dict objectForKey:@"ElimMatchListResults"]objectForKey:name] atIndex:finals.count];
            }
        }

        headers = [NSArray arrayWithObjects:@"Sweet 16", @"Quarterfinals", @"Semifinals", @"Finals", nil];
        sections = [NSArray arrayWithObjects:sweet16, quarterfinals, semi, finals, nil];

        // If the dictionary "dict" gets filled with data...

        if (dict) {

            [[self tableView]setDelegate:self];
            [[self tableView]setDataSource:self];

            // Now uses data storage so that the user only needs to initially connect to the internet and then they can keep the schedule afterwords

            [dataDict setObject: [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSArray arrayWithArray:sections], @"sections",
                                 [NSArray arrayWithArray:headers], @"headers",
                                                     nil]
                          forKey:@"Matches"];
             [dataDict writeToFile:path atomically:YES];
        }
        else{
            NSLog(@"%@", error);
        }

    }

    // Set the number of sections based on how many arrays the sections array has within it

    - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
       return [[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] count];
    }

    // Set the number of rows in each individual section based on the amount of objects in each array
    //   within the sections array

    - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
        return [[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:section] count];
    }

    // Set headers of sections from the "headers" array

    - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
        return [[[dataDict objectForKey:@"Matches"] objectForKey:@"headers"] objectAtIndex:section];
    }

    // Create cells as the user scrolls

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{


        NSLog(@"Entered Final Loop");

        static NSString *cellIdentifier = @"Cell";
        CustomCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

        if(!cell){
            cell = [[CustomCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
        }

        cell.matchNum.text = [[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"MatchID"];
        cell.red1.text = [NSString stringWithFormat:@"%@",[[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Red 1"]];
        cell.red2.text = [NSString stringWithFormat:@"%@",[[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Red 2"]];
        cell.redScore.text = [NSString stringWithFormat:@"%@", [[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Red Score"]];
        cell.blue1.text = [NSString stringWithFormat:@"%@",[[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Blue 1"]];
        cell.blue2.text = [NSString stringWithFormat:@"%@",[[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Blue 2"]];
        cell.bluescore.text = [NSString stringWithFormat:@"%@", [[[[[dataDict objectForKey:@"Matches"] objectForKey:@"sections"] objectAtIndex:indexPath.section] objectAtIndex:indexPath.row] objectForKey:@"Blue Score"]];


        return cell;
    }

对于冗长的代码，我深表歉意，我只是想确保我了解了所有详细信息。请提出您需要的任何问题以进行澄清，我现在真的很困惑和慌乱，不知道为什么如果没有互联网连接，它永远不会进入创建单元格的功能。

最佳答案

几个 react :

1. 您的 fileExistsAtPath 看起来不正确。当然你应该有完全合格的路径，例如:

   if (![[NSFileManager defaultManager] fileExistsAtPath:path]) {
       [[NSFileManager defaultManager] copyItemAtPath:[[NSBundle mainBundle]pathForResource:@"data" ofType:@"plist"] toPath:path error:nil];
   }
   

   我还可能建议您检查 copyItemAtPath 是否成功(返回值或使用 error 参数)。

2. 我假设您知道 data.plist 永远不会在 viewDidLoad 完成之前成功刷新(因为连接是异步启动的，您会立即从 initWithRequest)。此代码只是加载最后的 data.plist 值，同时检索新数据 yield (尽管有先前的错误)。这是你的期望吗？

3. 除我之前的观点外，您的 connectionDidFinishLoading 似乎没有发出对表的 reloadData 调用，所以您似乎总是看之前的数据。连接完成后，connectionDidFinishLoading 应该为 UITableView 调用 reloadData。

4. 不相关的次要细节，但我可能会在 NSURLConnectionDataDelegate 方法 didReceiveResponse 中初始化 receivedData(并且仅当该响应也成功了)。它并不真正属于 viewDidLoad。

5. 我可能还鼓励您检查 JSONObjectWithData 是否失败。一些网络故障表现为一个成功的 NSURLConnection 请求返回一个 HTML 页面 (!) 报告一个错误。该 HTML 页面将无法通过 JSONObjectWithData 处理。如果 JSONObjectWithData 返回 nil 或者如果 error 对象不是 nil，您可能想要中止您的解析例程。

关于ios - 缺少 Internet 连接会阻止创建单元格，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/17840528/