iphone - 向下滚动 uitableview 到特定日期

Question

我想知道我是否有一个合适的，每个表项的标题是一个日期和时间。如果我希望表格自动向下滚动到具有特定日期的单元格，我可以知道如何编码吗？今天的日期？我应该在 viewDidLoad 方法中编写什么代码？

这是我的表格代码，

@interface PictureListMainTable : UITableViewController{
    IBOutlet UIButton*scroll;

}

@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (strong, nonatomic) NSMutableArray *pictureListData;
@property (strong, nonatomic) IBOutlet UIButton*scroll;

- (void)readDataForTable;
-(IBAction)scrolldown:(id)sender;
@end



@synthesize managedObjectContext, pictureListData;
@synthesize scroll;



//  When the view reappears, read new data for table
- (void)viewWillAppear:(BOOL)animated
{
    //  Repopulate the array with new table data
    [self readDataForTable];
}

//  Grab data for table - this will be used whenever the list appears or reappears after an add/edit
- (void)readDataForTable
{
    //  Grab the data
    pictureListData = [CoreDataHelper getObjectsForEntity:@"Pictures" withSortKey:@"title" andSortAscending:YES andContext:managedObjectContext];

    //  Force table refresh
    [self.tableView reloadData];
}

#pragma mark - Actions

//  Button to log out of app (dismiss the modal view!)
- (IBAction)logoutButtonPressed:(id)sender
{
    [self dismissModalViewControllerAnimated:YES];
}

#pragma mark - Segue methods

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    //  Get a reference to our detail view
    PictureListDetail *pld = (PictureListDetail *)[segue destinationViewController];

    //  Pass the managed object context to the destination view controller
    pld.managedObjectContext = managedObjectContext;

    //  If we are editing a picture we need to pass some stuff, so check the segue title first
    if ([[segue identifier] isEqualToString:@"EditPicture"])
    {
        //  Get the row we selected to view
        NSInteger selectedIndex = [[self.tableView indexPathForSelectedRow] row];

        //  Pass the picture object from the table that we want to view
        pld.currentPicture = [pictureListData objectAtIndex:selectedIndex];
    }
}

#pragma mark - Table view data source

//  Return the number of sections in the table
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

//  Return the number of rows in the section (the amount of items in our array)
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [pictureListData count];
}

//  Create / reuse a table cell and configure it for display
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    // Get the core data object we need to use to populate this table cell
    Pictures *currentCell = [pictureListData objectAtIndex:indexPath.row];

    //  Fill in the cell contents
    cell.textLabel.text = [currentCell title];
    cell.detailTextLabel.text = [currentCell desc];

    //  If a picture exists then use it
    if ([currentCell smallPicture])
    {
        cell.imageView.contentMode = UIViewContentModeScaleAspectFit;
        cell.imageView.image = [UIImage imageWithData:[currentCell smallPicture]];
    }

    return cell;
}

//  Swipe to delete has been used.  Remove the table item
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete)
    {
        //  Get a reference to the table item in our data array
        Pictures *itemToDelete = [self.pictureListData objectAtIndex:indexPath.row];

        //  Delete the item in Core Data
        [self.managedObjectContext deleteObject:itemToDelete];

        //  Remove the item from our array
        [pictureListData removeObjectAtIndex:indexPath.row];

        //  Commit the deletion in core data
        NSError *error;
        if (![self.managedObjectContext save:&error])
            NSLog(@"Failed to delete picture item with error: %@", [error domain]);

        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
}

@end

谢谢

Answer 1

由于您要处理日期，因此最好创建一个日期数组并使用 dateComponents 查找当前日期。

在这段代码中，dates 是一个 NSDate 实例数组。

NSCalendar *cal = [NSCalendar currentCalendar];

NSDate *today = [NSDate date];
[self.dates enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    NSDate *date = (NSDate *)obj;
    NSDateComponents *components = [cal components:NSDayCalendarUnit
                                          fromDate:date
                                            toDate:today
                                           options:0];
    if ([components day]==0) {
        *stop = TRUE;
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:idx inSection:0];
        [self.tableView scrollToRowAtIndexPath:indexPath
                              atScrollPosition:UITableViewScrollPositionTop
                                      animated:YES];
    }
}];

编辑:

- (void)viewWillAppear:(BOOL)animated
{
    //  Repopulate the array with new table data
    [self readDataForTable];

    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    [dateFormatter setDateFormat:@"dd.MMMM - EEEE"];
    NSDate *today = [NSDate date];
    [pictureListData  enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        Pictures *picture = (Pictures *)obj;
        NSDate *date = [dateFormatter dateFromString:picture.title];
        NSDateComponents *components = [cal components:NSDayCalendarUnit
                                              fromDate:date
                                                toDate:today
                                               options:0];
        if ([components day]==0) {
            *stop = TRUE;
            NSIndexPath *indexPath = [NSIndexPath indexPathForRow:idx inSection:0];
            [self.tableView scrollToRowAtIndexPath:indexPath
                                  atScrollPosition:UITableViewScrollPositionTop
                                          animated:YES];
        }
    }];
}