奇怪的Tableview滚动行为

Question

I've got two views, each of which contains a tableview. They are identical in every respect except the height. They are each fed data from the same entity (currently filled with gibberish) in my Core Data store.

One of them works perfectly when scrolled, the other behaves differently. The problem is that the cells scroll past the top section header. Succeeding section titles bump older ones up as expected, and the header title slides up along with the cells.

Here are a couple of screenshots that I hope will illustrate the issue:

First, the one that works properly:

"A" is the top section header, and the cells don't scroll past it.

The next two shots are of the tableview that's behaving weirdly. I've added some arrows to show what's happening:

I've compared the settings in the Attributes Inspector, and unless I've overlooked something, they appear identical.

Anyone have any ideas?

Thanks!

Edit:

Here's the code from the associated UIViewController which is the delegate and the datasource for the TableView:

//
//  AvsAViewController.m
//  WMDGx
//
//  Created by Tim Jones on 2/6/14.
//  Copyright (c) 2014 TDJ. All rights reserved.
//

#import "AvsAViewController.h"

@interface AvsAViewController ()
{
    NSFetchedResultsController *frc;
}

@end

@implementation AvsAViewController

- (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.
    [self refreshData];
}

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

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

// Customize the appearance of table view cells.
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {

    // Configure the cell to show the activity's name
    ListActivity *thisActivity = [frc objectAtIndexPath:indexPath];
    cell.textLabel.text = thisActivity.activityName;
}


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

    [self configureCell:cell atIndexPath:indexPath];

    cell.textLabel.textColor = [UIColor redColor];
    NSAttributedString *attString;
    attString = cell.textLabel.attributedText;
    return cell;
}


//     Section Label

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    NSString *sectionLabel = [[[frc sections] objectAtIndex:section]name];
    return [sectionLabel uppercaseString];
}

-(void) refreshData
{
    //This was the turning point for proper MR grouping. The two Properties (activityCategory and activityName) are used as Sort descriptors in the underlying core data methods

    frc = [ListActivity MR_fetchAllSortedBy:@"activityCategory,activityName"
                                  ascending:YES withPredicate:nil
                                    groupBy:@"activityCategory"
                                   delegate:nil];
    [self.myTableView reloadData];
}


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

@end

Answer 1

确保在“属性”检查器中为该UITableView选择了“ Clip Subviews”，并且在代码中某处未将表的clipsToBounds设置为NO 。

Answer 2

I resolved the issue by simply deleting the TableView and dragging in a new one, wiring it up. The problem is therefore fixed, but I have no idea what caused it.

Thanks to @drhr, who commented, and all others who took a look!

Edit:

Just wondering if anyone else has run across this problem. I just had it repeat on another tableview, and had to resolve it as above. FWIW, I'm using Xcode 5, and developing an iPhone app.

I guess fixed is good, but it would be nice to actually know what caused the problem.