ios reloadData 仅重新加载不可见的单元格

Posted 2023-02-27

【中文标题】ios reloadData 仅重新加载不可见的单元格

【英文标题】：ios reloadData only reloading non visible cells

【发布时间】：2013-03-25 03:39:11

【问题描述】：

我在这里阅读了很多关于我的问题的帖子，但没有一个有效，所以提前感谢您的帮助。

我有一个表格视图，可以加载自定义笔尖。我有来自网络 JSON 文件的数据。我已经实现了一个刷新调用（我现在只需点击一个单元格就可以覆盖它）。

调用该方法时，会调用并解析新的 JSON。并且单元格更新了。我可以通过向下滚动表格视图来确认这一点，我可以看到新的行。但可见的行仍然存在。

我试图使数组为零，循环遍历并根据对象删除，但似乎没有任何效果。

这里是代码

#import "MMNewsViewController.h"
#import "MMCatsDetailController.h"
#import "CellView.h"
#import "FeatureCell.h"
//#import "MMnewsData.h"



@interface MMNewsViewController ()

@end

@implementation MMNewsViewController
@synthesize titleData;
@synthesize imageData;
@synthesize imageLargeData;
@synthesize dateData;
@synthesize descriptionData;
@synthesize linkData;
@synthesize cityData;

@synthesize _jsonResult;
@synthesize _jsonResultImage;
@synthesize _jsonResultImageLarge;
@synthesize _jsonResultDate;
@synthesize _jsonResultDescription;
@synthesize _jsonResultLink;
@synthesize _jsonResultCity;
@synthesize featureImage;
@synthesize region;





- (void)viewDidLoad

    [super viewDidLoad];

    UINib *nib = [UINib nibWithNibName:@"CellView" bundle:nil];
    [self.tableView registerNib:nib forCellReuseIdentifier:@"CellView"];

    [self.navigationController.navigationBar setTintColor:[UIColor blackColor]];
    self.tabBarItem = [[UITabBarItem alloc] initWithTabBarSystemItem:UITabBarSystemItemFeatured tag:0];

    self.navigationController.title = @"News";

    self.tabBarItem.title = @"FooBar";
    self.title = @"Music News";



 UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];

refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"Pull to Refresh"];

[refreshControl addTarget:self action:@selector(refreshView:)        
forControlEvents:UIControlEventValueChanged];

[self.view addSubview:refreshControl];
[self.tableView deselectRowAtIndexPath:[self.tableView indexPathForSelectedRow] animated:YES];

    region = @"wellington";
    [self makeDataRequests];




-(void)makeDataRequests



    NSString *strURL = [NSString stringWithFormat:@"MYSITEjson.php?region=%@",region  ];



    NSMutableData *dataURL = [NSData dataWithContentsOfURL:[NSURL URLWithString:strURL] ];
    NSMutableDictionary *arrayResult = [NSJSONSerialization JSONObjectWithData:dataURL options:kNilOptions    error:nil];

    NSMutableArray *dataArray = [arrayResult objectForKey:@"tickets"]; //2

    _jsonResult = [[NSMutableArray alloc] init];
    _jsonResultImage = [[NSMutableArray alloc] init];
    _jsonResultImageLarge = [[NSMutableArray alloc] init];
    _jsonResultDate= [[NSMutableArray alloc] init];
    _jsonResultDescription= [[NSMutableArray alloc] init];
    _jsonResultLink= [[NSMutableArray alloc] init];
    _jsonResultCity= [[NSMutableArray alloc] init];


    for(NSMutableDictionary *newsDict in dataArray)
        NSMutableDictionary *titleDict = [newsDict objectForKey:@"title"];
        NSMutableDictionary *imageDict = [newsDict objectForKey:@"image"];
        NSMutableDictionary *imageLargeDict = [newsDict objectForKey:@"imageLarge"];
        NSMutableDictionary *dateDict = [newsDict objectForKey:@"pubDate"];
        NSMutableDictionary *descriptionDict = [newsDict objectForKey:@"description"];
        NSMutableDictionary *linkDict = [newsDict objectForKey:@"link"];

       NSMutableDictionary *cityDict = [[newsDict objectForKey:@"venue"] objectForKey:@"city"];


        [_jsonResult addObject:titleDict];
        [_jsonResultImage addObject:imageDict];
        [_jsonResultImageLarge addObject:imageLargeDict];
        [_jsonResultDate addObject:dateDict];
        [_jsonResultDescription addObject:descriptionDict];
        [_jsonResultLink addObject:linkDict];
         [_jsonResultCity addObject:cityDict];
       //  NSLog(@"%@",cityDict);

    

    //   NSString *strResult = [[NSString alloc] initWithData:dataURL encoding:NSUTF8StringEncoding];



    self.titleData = _jsonResult;
    self.imageData = _jsonResultImage;
    self.imageLargeData = _jsonResultImageLarge;
    self.dateData = _jsonResultDate;
    self.descriptionData = _jsonResultDescription;
    self.linkData = _jsonResultLink;
    self.cityData = _jsonResultCity;


[self performSelector:@selector(delayedReloadData) withObject:nil afterDelay:1.5];

-(void) delayedReloadData


     NSLog(@"delayedReloadData");
   [self.tableView reloadData];



- (void)reloadRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation

       NSLog(@"reloadRowsAtIndexPaths");



- (void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


#pragma mark - Table view data source


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



    NSLog(@"COUNTER: %i",[self.titleData count]);
    // Return the number of rows in the section.
   return [self.titleData count];



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

      NSLog(@"cellForRowAtIndexPath");

   NSUInteger row  = [indexPath row];



        static NSString *CellIdentifier = @"CellView";

        CellView *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

        if (cell == nil)
            NSLog(@"New Cell Made");

            NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"CellView" owner:nil options:nil];

            for(id currentObject in topLevelObjects)
            
                if([currentObject isKindOfClass:[CellView class]])
                
                    cell = (CellView *)currentObject;
                    break;
                
            
        



         [[cell titleLabel] setText:[titleData objectAtIndex:row]];
         [[cell dateLabel] setText:[cityData objectAtIndex:row]];

        NSData *data = [NSData dataWithContentsOfURL: [NSURL URLWithString:[imageData objectAtIndex:row]]];
        UIImage *img1 = [UIImage imageWithData:data];
        [[cell imageLabel] setImage:img1];

        return cell;


    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;





#pragma mark - Table view delegate
- (void)deselectRowAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated



- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

    // Navigation logic may go here. Create and push another view controller.

     MMCatsDetailController *detailViewController = [[MMCatsDetailController alloc] initWithNibName:@"MMCatsDetailController" bundle:nil];



    NSUInteger row  = [indexPath row];
    NSString *titleSender = [titleData objectAtIndex:row];
    NSString *dateSender = [dateData objectAtIndex:row];
    NSString *imageSender = [imageData objectAtIndex:row];
    NSString *imageLargeSender = [imageLargeData objectAtIndex:row];
    NSString *descriptionSender = [descriptionData objectAtIndex:row];
    NSString *linkSender = [linkData objectAtIndex:row];

    detailViewController.titleSend = titleSender;
    detailViewController.dateSend = dateSender;
    detailViewController.imageSend = imageSender;
    detailViewController.imageLargeSend = imageLargeSender;
    detailViewController.descriptionSend = descriptionSender;
    detailViewController.linkSend = linkSender;

      //NSLog(@"linkSender=%@",linkSender);
        region = @"nelson";
[self makeDataRequests];
    //   [self.navigationController pushViewController:detailViewController animated:YES];
  [tableView deselectRowAtIndexPath:indexPath animated:YES];


-(void)refreshView:(UIRefreshControl *)refresh 
       refresh.attributedTitle = [[NSAttributedString alloc] initWithString:@"Refreshing data..."];
       // custom refresh logic would be placed here...
         region = @"nelson";
    [self makeDataRequests];


    NSLog(@"HEre");

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"MMM d, h:mm a"];
      NSString *lastUpdated = [NSString stringWithFormat:@"Last updated on %@",

                                        [formatter stringFromDate:[NSDate date]]];
    refresh.attributedTitle = [[NSAttributedString alloc] initWithString:lastUpdated];

      [refresh endRefreshing];
     NSLog(@"HEre");

 

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
     NSLog(@"numberOfSectionsInTableView");
    return 1;


 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath

    NSUInteger row  = [indexPath row];

    if(row==0)
   //     return 200;
    
    else


//    return 96;

          
      return 96;



 - (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section



    UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0,0,tableView.frame.size.width,10)];

    UILabel *headerLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, headerView.frame.size.width, headerView.frame.size.height)];

    headerLabel.font = [UIFont boldSystemFontOfSize:12];
    headerLabel.text = @"Music News";
    headerLabel.backgroundColor = [UIColor blackColor];
     headerLabel.textColor = [UIColor whiteColor];
    [headerView addSubview:headerLabel];

    return headerView;




@end

【问题讨论】：

您好，感谢您的 cmets 和建议。生病阅读更多关于 CGD 和主线程。主要问题出在 XIB 上——我为视图及其包含的表设置了文件所有者。 ARGH - 哦，现在整理得很好

抱歉，我有点不明白这个问题。你能解释一下“但是可见的行仍然存在”是什么意思吗？

【参考方案1】：

您需要做的就是在 tableView 上调用 reloaddata。要么你没有在你认为正在调用它的 tableView 上调用 reloaddata，要么你的单元格没有在 tableView:cellForRowAtIndexPath: 中正确设置，或者你在不在主线程上时调用了 reloaddata。

您不应该从您的 UI 线程对服务器进行同步调用。稍微了解一下 GCD。当对服务进行非阻塞调用时，函数 dispatch_async 会派上用场。

【讨论】：

查看您的代码后。我认为您可能在单独的线程上调用 reloaddata 。尝试这样做：dispatch_async(dispatch_get_main_queue(), ^ [self.tableView reloadData; ];

您好，感谢您的 cmets。似乎我有 [self.tableView reloadData];或 [self.tableView performSelectorOnMainThread:@selector(delayedReloadData) withObject:nil waitUntilDone:NO];他们似乎都在做同样的事情。它们都调用 cellForRowAtIndexPath、numberOfRowsInSection、numberOfSectionsInTableView。没有被调用的一件事是 reloadRowsAtIndexPaths。

【参考方案2】：

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

static NSString *simpleTableIdentifier = @"CueTableCell";

CueTableCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];

if (cell == nil) 
    NSArray *array = [[NSBundle mainBundle] loadNibNamed:@"CueTableCell XibName" owner:self options:nil];
    // Grab a pointer to the first object (presumably the custom cell, as that's all the XIB should contain).
    cell = [array objectAtIndex:0];


return cell;

【讨论】：

除了加载笔尖的方式略有不同之外，这有什么不同？