Question

在我努力学习如何将数据正确加载到Core Data的分组表视图中时，我构建了一个非常简单的小型双视图应用程序。我使用MagicalRecord作为我与CD的接口。

当前的问题是，当输入数据按预期保存到我的商店时，表格视图在保存时不会刷新以显示新数据。但是，如果我在模拟器中停止应用程序，然后从Xcode重新启动，新数据将显示在tableview中。

我正在使用NotificationCenter而不是委托进行通信。这是我最初的View Controller（包含和委托给tableview）的代码，后面是AddViewController中用来添加数据的代码。有魔法记忆经验的人能否对我有所启发？谢谢！

//
//  ViewController.m
//  MRGroupingTest
//
//  Created by Tim Jones on 1/9/14.
//  Copyright (c) 2014 TDJ. All rights reserved.
//

#import "ViewController.h"
#import "ListActivity.h"

@interface ViewController ()

{
    NSFetchedResultsController *frc;
}


@end

@implementation ViewController

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

    [self refreshData];
    frc = [ListActivity MR_fetchAllGroupedBy:@"category" withPredicate:nil sortedBy:@"name" ascending:YES];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(notificationNewActivityAdded:) name:@"newActivityAdded" object:nil];

}

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

-(void) notificationNewActivityAdded:(NSNotification*)notification
{
    [self.myTableView reloadData];
}



#pragma mark Table View data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return [[frc sections] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    id<NSFetchedResultsSectionInfo> sectionInfo = [[frc sections] objectAtIndex:section];
    int rows = [sectionInfo numberOfObjects];
    return rows;

}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> sectionInfo = [[frc sections] objectAtIndex:section];
    return [sectionInfo name];

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    // Configure the cell...
    if ([frc sections] > 0)
    {
        ListActivity *activity = [frc objectAtIndexPath:indexPath];
        cell.textLabel.text = activity.name;

    }

    return cell;

}

-(void) refreshData
{

    frc = [ListActivity MR_fetchAllGroupedBy:@"category" withPredicate:nil sortedBy:@"name" ascending:YES];

    [self.myTableView reloadData];
}


#pragma mark Table View delegate

@end

这是来自AddViewController的代码：

//
//  AddViewController.m
//  MRGroupingTest
//
//  Created by Tim Jones on 1/9/14.
//  Copyright (c) 2014 TDJ. All rights reserved.
//

#import "AddViewController.h"

@interface AddViewController ()

@end

@implementation AddViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}

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

- (IBAction)saveAction:(UIBarButtonItem *)sender
{
    NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];

    ListActivity * thisActivity = [ListActivity MR_createInContext:localContext];
    thisActivity.name =  self.activityField.text;
    thisActivity.category = self.categoryField.text;
    [localContext MR_saveToPersistentStoreAndWait];
    //Inform app
    [[NSNotificationCenter defaultCenter] postNotificationName:@"newActivityAdded" object:localContext];
    //dismiss view
    [self.navigationController dismissViewControllerAnimated:YES completion:nil];


}

- (IBAction)cancelAction:(UIBarButtonItem *)sender
{
    NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"newActivityAdded" object:localContext];
    //dismiss view
    [self.navigationController dismissViewControllerAnimated:YES completion:nil];

}


@end

Answer 1

您需要重新加载TableView数据，即调用reloadData函数

iOS为什么我的应用程序在重新启动之前不会将数据加载到tableview中？

1 个答案: