即使在主线程上调用重新加载，UITable 也不会刷新

Question

我有一个带有 UITable 和导航控制器的主视图控制器 (SecondViewController)。按下导航栏按钮时，菜单会从 table 顶部的导航栏下拉。这个菜单是通过添加一个视图控制器作为子视图创建的，如下所示：

//SecondViewController.m
self = sortMenu.secondVC;
[self addChildViewController:sortMenu];
[self.view addSubview:sortMenu.view];
[sortMenu didMoveToParentViewController:self];

sortMenu 包含一个按钮，该按钮通过调用主视图控制器的 class 方法来更改单元格的显示顺序。

//SortMenuViewController.m
- (IBAction)sortButtonPressed:(id)sender {
    [_secondVC sortButtonPressed:[sender tag]];

}

在 sortButtonPressed 中，它调用一个方法来发出具有更新的排序过滤器值的提取请求。

//SecondViewController.m
-(void)sortButtonPressed:(NSInteger)sortDescriptor{
    _sortDescriptor = sortDescriptor;
    currentPredicate = [NSPredicate predicateWithFormat:@"dataset & %d > 0", 4];
    [self fetchResultsUsingSegmentedControlIndex];
}

提取请求已执行，returns数据按新顺序排列。

//SecondViewController.m
- (IBAction)fetchResultsUsingSegmentedControlIndex
{
    NSString* sectionNameKeyPath = nil;
    NSArray* sortDescriptors = nil;
    NSSortDescriptor *scientificNameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"scientificName" ascending:YES];
    NSSortDescriptor *commonNameFirstDescriptor = [[NSSortDescriptor alloc] initWithKey:@"commonNameFirst" ascending:YES];
    NSSortDescriptor *commonNameLastDescriptor = [[NSSortDescriptor alloc]
                                                  initWithKey:@"commonNameLast"
                                                  ascending:YES
                                                  selector:@selector(localizedCaseInsensitiveCompare:)];

    if (_sortDescriptor == kSortByCommonNameFirst )
    {
        sortDescriptors = [[NSArray alloc] initWithObjects:commonNameFirstDescriptor, commonNameLastDescriptor, scientificNameDescriptor, nil];
        sectionNameKeyPath = @"commonNameFirst";
    }
    else if (_sortDescriptor == kSortByCommonNameLast )
    {
        sortDescriptors = [[NSArray alloc] initWithObjects:commonNameLastDescriptor, commonNameFirstDescriptor, scientificNameDescriptor, nil];
        sectionNameKeyPath = @"commonNameLast";
    }
    else if (_sortDescriptor == kSortByScientificName )
    {
        sortDescriptors = [[NSArray alloc] initWithObjects:scientificNameDescriptor, commonNameFirstDescriptor, commonNameLastDescriptor, nil];
        sectionNameKeyPath = @"scientificName";
    }

    NSError *error;

    NSLog(@"current predicate: %@", currentPredicate);

    [[self fetchedResultsControllerWithsectionNameKeyPath:sectionNameKeyPath sortDescriptors:sortDescriptors predicate:currentPredicate] performFetch:&error];


    [scientificNameDescriptor release];
    [commonNameLastDescriptor release];
    [commonNameFirstDescriptor release];
    [sortDescriptors release];

    NSUInteger sectionsCt = [[speciesFetchedResultsController sections] count];
    int sum = 0;
    for (int i=1; i < sectionsCt; i++){
        id <NSFetchedResultsSectionInfo> sectionInfo = [[speciesFetchedResultsController sections] objectAtIndex:i];
        NSUInteger numOfObj = [sectionInfo numberOfObjects];
        NSLog(@" in section %d number of objects is  %lu ", i, (unsigned long)numOfObj);
        sum  = sum + numOfObj;
    }


    [_table performSelectorOnMainThread:@selector(reloadData)
                                     withObject:nil
                                  waitUntilDone:NO];
}

当我从主视图控制器调用 fetchResultsUsingSegmentedControlIndex 时（在下拉排序菜单之前），它工作正常。但是，当从 sortMenu 调用时，不会调用 numberOfRowsInSection、numberOfSectionsInTableView 和 cellForRowAtIndexPath。我试图用 performSelectorOnMainThread 在主线程上调用 reloadData 并将其分派到主队列，但都不起作用。

我最初通过在按下导航栏按钮时向主视图控制器添加一个 pickerview 创建了一个排序菜单，并且我的 table 重新加载正确。由于为菜单创建了一个单独的视图控制器（以获得更好的设计控制），它不起作用。

Answer 1

最终使用委托。

//  SortMenuViewController.h

#import <UIKit/UIKit.h>

@protocol SortMenuViewControllerDelegate <NSObject>
-(void)sortButtonPressed:(NSInteger)sortDescriptor;
-(void)viewButtonPressed:(NSInteger)viewDescriptor;
@end

@interface SortMenuViewController : UIViewController{

}

//SortMenuViewController.m
- (IBAction)changeSort:(id)sender {

    [_delegate sortButtonPressed:[sender tag]];

}

//SecondViewController.h
@interface SecondViewController : UIViewController <NSFetchedResultsControllerDelegate, SortMenuViewControllerDelegate>{

}
-(void)sortButtonPressed:(NSInteger)sortDescriptor{
    _sortDescriptor = sortDescriptor;
    currentPredicate = [NSPredicate predicateWithFormat:@"dataset & %d > 0", dataset];
    [self fetchResultsUsingSegmentedControlIndex];
}

即使在主线程上调用重新加载，UITable 也不会刷新

UITable won't refresh even with reload called on main thread

multithreading

objective-c

reloaddata

ios