ios - 缺乏互联网连接会阻止细胞的创建

Question

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，并且它们很好地显示了每个单独匹配的数据。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，一旦应用程序按顺序被终止，用户不一定需要重新连接到互联网查看当天的比赛日程。我的代码可以完美运行，直到我无法连接到互联网。由于某种原因，一旦互联网连接失败，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，以便澄清，我现在真的很困惑，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函数。

Answer 1

一些 react :

1. 您的 fileExistsAtPath 看起来不正确。当然你应该有完全限定的路径，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. 我假设您知道在 viewDidLoad 完成之前 data.plist 永远不会成功刷新(因为连接是异步启动的，并且您立即从initWithRequest)。此代码只是加载最后的 data.plist 值，同时检索新数据(尽管存在先前的错误)。这是你的期望吗？

3. 除了我之前的观点之外，您的 connectionDidFinishLoading 似乎并未对表发出 reloadData 调用，因此您似乎总是会参见之前的数据。连接完成后，connectionDidFinishLoading 应为 UITableView 调用 reloadData。

4. 次要的、不相关的细节，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. 我还鼓励您检查 JSONObjectWithData 是否失败。某些网络故障表现为成功的 NSURLConnection 请求，该请求返返回告错误的 HTML 页面 (!)。该 HTML 页面将无法处理 JSONObjectWithData。如果 JSONObjectWithData 返回 nil 或 error 对象不是 nil，您可能想要中止解析例程。