iOS - [UITableView reloadData] reloads, but not removes old cells?

Question

This is weird, I know but my [UITableView reloadData] is not removing old cells, like this: enter image description here

The mess you see happened after I clicked on the + button, came back and changed values again. plus button pushes the navigationController to an another controller, and after I came back with clicking on the back button and changed the value, this is what I see. How is it possible?? I used a custom view (subclassed from UIView), which I created as a UIStepper with a UILabel. Here is the codes, the controller.m, and the .h-.m files for the custom UIView.

controller.m

@interface ViewController ()
@property NSString *docsDir;
@property sqlite3 *DB;
@property NSArray *dirPaths;
@property NSString* databasePath;
@property (strong, nonatomic) IBOutlet UITableView *tableView;
@property BOOL isCreatedBefore;
@property NSArray *theList;
@end

@implementation ViewController
@synthesize docsDir;
@synthesize DB;
@synthesize dirPaths;
@synthesize databasePath;
- (void)viewDidLoad
{
    [super viewDidLoad];
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = [dirPaths objectAtIndex:0];
    databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: [NSString stringWithFormat:@"database.db"]]];

    [self createDatabase];
    self.theList = [self readAllEntries];
}

-(void) viewWillAppear:(BOOL)animated{
    self.theList = [self readAllEntries];
    [self.tableView reloadData];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.theList count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{   SeriesObject * obj = [self.theList objectAtIndex:indexPath.row];
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cellocan"];
    UILabel *nameLabel = (UILabel *)[cell.contentView viewWithTag:1];
    [nameLabel setText:obj.name];

    CounterView *seasonCounter = [[CounterView alloc] initWithX:220 WithY:28 WithName:obj.name withCount:obj.session withCustomTag:indexPath.row];
    seasonCounter.tag = 2;
    CounterView *episodeCounter = [[CounterView alloc] initWithX:268 WithY:28 WithName:obj.name withCount:obj.episode withCustomTag:indexPath.row];
    episodeCounter.tag = 4;

    [cell.contentView addSubview:seasonCounter];
    [cell.contentView addSubview:episodeCounter];

    return cell;
}


- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
    // Return YES if you want the specified item to be editable.
    return YES;
}

// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        SeriesObject *obj = [self.theList objectAtIndex:indexPath.row];
        [self deleteEntryWithID:obj.idd];

        self.theList = [self readAllEntries];
        [self.tableView reloadData];
    }
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
    return 88;
}



- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:YES];

}

______and more about reading from database or deleting; not about the view. (this is a very simple app, as a free time hobby; so I didn't spend time to follow MVC)

CounterView.h

@interface CounterView : UIView
@property NSString* name;
@property NSInteger count;
@property UILabel *label;
@property NSInteger customTag;

- (id)initWithX:(CGFloat)xPoint WithY:(CGFloat)yPoint WithName:(NSString*)newName withCount:(NSInteger)newCount withCustomTag:(NSInteger)newTag;
@end

CounterView.m

@interface CounterView()

@property NSString *docsDir;
@property sqlite3 *DB;
@property NSArray *dirPaths;
@property NSString* databasePath;

@end


@implementation CounterView

@synthesize docsDir;
@synthesize DB;
@synthesize dirPaths;
@synthesize databasePath;

- (id)initWithX:(CGFloat)xPoint WithY:(CGFloat)yPoint WithName:(NSString*)newName withCount:(NSInteger)newCount withCustomTag:(NSInteger)newTag
{
    self = [super initWithFrame:CGRectMake(xPoint, yPoint, 24, 52)];
    if (self) {
        self.customTag = newTag;
        self.count = newCount;
        self.name = newName;

        UIButton *btnUp = [[UIButton alloc] initWithFrame:CGRectMake(3, 2, 18, 12)];
        [btnUp setImage:[UIImage imageNamed:@"top.png"] forState:UIControlStateNormal];
        [btnUp addTarget:self action:@selector(increaseValue) forControlEvents:UIControlEventTouchUpInside];
        UIButton *btnDown = [[UIButton alloc] initWithFrame:CGRectMake(3, 38, 18, 12)];
        [btnDown setImage:[UIImage imageNamed:@"bottom.png"] forState:UIControlStateNormal];
        [btnDown addTarget:self action:@selector(decreaseValue) forControlEvents:UIControlEventTouchUpInside];
        self.label = [[UILabel alloc] initWithFrame:CGRectMake(0, 14, 24, 24)];
        [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];
        self.label.textAlignment = NSTextAlignmentCenter;

        [self addSubview:btnUp];
        [self addSubview:btnDown];
        [self addSubview:self.label];
    }
    return self;
}

- (void)addTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents{

}


-(void) increaseValue{
    self.count++;
    [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];
}
-(void) decreaseValue{
    self.count--;
    [self.label setText:[NSString stringWithFormat:@"%ld", (long)self.count]];
}

____and some more database codes too..

score 4 · Answer 1 · answered Mar 05 '14 at 21:54

4

In your cellForRowAtIndexPath: you are adding a subview every time. Cells are reused by UITableView, so when you reload you're getting a "dirty" cell. You need to check if the view is already there. If so, modify the view instead of adding one. Google "UITableViewCell viewWithTag" to see some sample code.

answered Mar 05 '14 at 21:54

Aaron Brager

65,323
19
161
287

I used it before. So it happened every time but because of the stabile contents, I never realise. Thanks.. – Arda Oğul Üçpınar Mar 05 '14 at 21:56
@Esq The pattern has been written hundreds of times and is easy to find. – Aaron Brager Jan 16 '15 at 15:52

score 3 · Answer 2 · edited Mar 05 '14 at 21:59

3

- (void)prepareForReuse
{
    //remove your subviews here 
    [self.subViewToRemove removeFromSuperView];
}

edited Mar 05 '14 at 21:59

Peter Bratton

6,302
6
39
61

answered Mar 05 '14 at 21:57

ManicMonkOnMac

1,476
13
21

score 1 · Answer 3 · answered Mar 05 '14 at 22:02

I would recommend that you create a custom cell class derived from UITableViewCell and have it include your custom CounterView instances. In this case you won't need to add the subviews each time in your cellForRowAtIndexPath (Which is causing the problem you're having), you can instead pass it whatever values it requires.

score 1 · Accepted Answer · answered Mar 05 '14 at 22:21

1

after some modifications, using this in the cellForRowAtIndexpath: method solved everything. Thanks everyone.

if (cell != nil)
    {
        NSArray* subviews = [cell.contentView subviews];
        for (UIView* view in subviews)
        {
            [view removeFromSuperview];
        }
    }

answered Mar 05 '14 at 22:21

Arda Oğul Üçpınar

881
1
14
38

This will work in a pinch, but if your cells get complex this approach can make your scrolling feel choppy. It's faster to reuse views than to remove and add them. – Aaron Brager Mar 05 '14 at 22:29

iOS - [UITableView reloadData] reloads, but not removes old cells?

4 Answers4