数据不会从 JSON 解析加载到某些 Tableview 单元格上

Posted 2023-03-04

【中文标题】数据不会从 JSON 解析加载到某些 Tableview 单元格上

【英文标题】：Data dosen't load on some Tableview cell from JSON parse

【发布时间】：2016-01-18 06:13:33

【问题描述】：

我在 XCODE 7.1 上制作了简单的应用程序。 我只在 tableview 单元格中显示 2 个标签和 1 个图像。我正在解析来自这个 URL 的数据。我只是在 Tableview 中加载数据这里我把 ViewController.m 文件的代码

    @interface ViewController ()

@end

@implementation ViewController
- (void)viewDidLoad 
    [super viewDidLoad];
UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    activityIndicator.alpha = 1.0;
    [self.view addSubview:activityIndicator];
    activityIndicator.center = CGPointMake([[UIScreen mainScreen]bounds].size.width/2, [[UIScreen mainScreen]bounds].size.height/2);
    [activityIndicator startAnimating];//to start animating
    // Do any additional setup after loading the view, typically from a nib.


    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];


    NSURL *URL = [NSURL URLWithString:@"http://www.androidbegin.com/tutorial/jsonparsetutorial.txt"];
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];
    NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) 
        if (error) 
            NSLog(@"Error: %@", error);
         else 
            [activityIndicator stopAnimating];
            _responsedic = (NSDictionary*) responseObject;
            _Worldpopulation = [_responsedic valueForKey:@"worldpopulation"];
            _imageURL = [_Worldpopulation valueForKey:@"flag"];
            _country = [_Worldpopulation valueForKey:@"country"];
            _population = [_Worldpopulation valueForKey:@"population"];
            NSLog(@"Data:%@",_imageURL);
            NSLog(@"Population",_population);
            NSLog(@"Country",_country);
           // NSLog(@"%@",_MovieList);
            //NSLog(@"Array: %@",_imageURL);
            //NSLog(@"%@",responseObject);
        
    ];
    [dataTask resume];



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

-(NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
    return 10;

-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    NSString *Identifier = @"mycell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:Identifier];
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:Identifier];
    // Set and load the images
    [cell.imageView sd_setImageWithURL:[_imageURL objectAtIndex:indexPath.row] placeholderImage:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) 

        // Get rid of the activity indicator when the image has been loaded
    ];




    cell.textLabel.text = [_country objectAtIndex:indexPath.row];
    cell.detailTextLabel.text = [_population objectAtIndex:indexPath.row];
    return  cell;


- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
    //NSString *rowValue = self.friends[indexPath.row+1];
    NSString *message = [[NSString alloc] initWithFormat:@"You selected %@",[_country objectAtIndex:indexPath.row]];

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"YOU SELECT"
                                                    message:message
                                                   delegate:self
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles:nil];
    [alert show];

我正在使用AFNetworking 3.0 和SDWebImage 进行图像加载。数据解析成功并显示在tableview 中。我在下面附上了屏幕截图

问题是所有数据都没有显示在 tableview 单元格中我还在成功加载但未显示在单元格中的 tableview 数据的每个单元格上放置了警报对话框。我到处搜索我找不到解决方案我正在使用 3G 连接所以网速不是问题请有人帮忙。

【问题讨论】：

您在单元格的非常不稳定的状态下开始异步操作，此外，出列单元格使其变得更加复杂。我之前在使用 SDWebImage 时遇到过这样的问题，我不得不在 UITableViewCell 的子类中移动加载图像（仍然使用 SDWebImage）以更好地处理 prepareForReuse 的情况等等。您需要取消以前的操作，以防您的单元格出队...

是的，但我如何从 UITableView 的 单元格子类加载图像。

【参考方案1】：

尝试使用完成块中的更新数据重新加载表视图。

NSURL *URL = [NSURL URLWithString:@"http://www.androidbegin.com/tutorial/jsonparsetutorial.txt"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) 
    if (error) 
        NSLog(@"Error: %@", error);
     else 
        [activityIndicator stopAnimating];
        _responsedic = (NSDictionary*) responseObject;
        _Worldpopulation = [_responsedic valueForKey:@"worldpopulation"];
        _imageURL = [_Worldpopulation valueForKey:@"flag"];
        _country = [_Worldpopulation valueForKey:@"country"];
        _population = [_Worldpopulation valueForKey:@"population"];
        NSLog(@"Data:%@",_imageURL);
        NSLog(@"Population",_population);
        NSLog(@"Country",_country);
       // NSLog(@"%@",_MovieList);
        //NSLog(@"Array: %@",_imageURL);
        //NSLog(@"%@",responseObject);


        //Added Code -> Reloading data on Main queue for update
        dispatch_async(dispatch_get_main_queue(), ^

            [self.tableview reloadData];
        ); 
    
];
[dataTask resume];

希望对您有所帮助。 谢谢。

【参考方案2】：

1）解析数据并获取数据后重新加载表

 -(void)ParseData
    


            NSURLSession * session = [NSURLSession sharedSession];

            NSURL * url = [NSURL URLWithString: @"http://www.androidbegin.com/tutorial/jsonparsetutorial.txt"];

            //Create  URLReques
            NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
                                                                   cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                               timeoutInterval:60.0];



            [request addValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];



            // Set Method POST/GET
            [request setHTTPMethod:@"GET"];


            // Asynchronously Api is hit here

            NSURLSessionDataTask* dataTask=[session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) 


                if (!error) //If error nil
                
                    //Serialization  data
                    NSDictionary * json  = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];

                    NSLog(@"json %@",json);

                    array=[json valueForKey:@"worldpopulation"];


                dispatch_async(dispatch_get_main_queue(), ^(void) 
                    if(array.count!=0)
                    

                        //Reload table View
                        [_tblView reloadData];
                    
                );

                
                else
                
                    //failure;
                

            ];


            [dataTask resume] ; // Executed task

    


2) Table View DataSource



 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
    

        if(array.count!=0)
        
            return [array count];
        
        return 0;
    


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

        static NSString *CellIdentifier = @"Cell";
        UITableViewCell *cell;
        //= [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
        cell.backgroundColor =[UIColor whiteColor];



        cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

        UILabel *lblCountry=(UILabel*)[cell viewWithTag:2];
        lblCountry.text= [[array objectAtIndex:indexPath.row]valueForKey:@"country"];

        UILabel *lblPopulation=(UILabel*)[cell viewWithTag:3];
        lblPopulation.text= [[array objectAtIndex:indexPath.row]valueForKey:@"population"];

        UIImageView *img = (UIImageView *)[cell viewWithTag:1];


        [img setImageWithURL:[NSURL URLWithString:[[array objectAtIndex:indexPath.row]valueForKey:@"flag"]]];

        return cell;