label display text not well when use [cell setNeedsDisplay] - ios

Question

I have a UICollectionView to display username of user, and when I add new or modify a user -> I will update into database -> then get all data again(from the data base). and then reload UICollectionView. All I want is: if I modify a user at index 3 then after reload this user is still stay at index 3(and if I add a new user this user will display at the end position). So that I use setNeedsDisplay. But I have a problem that my label display text not well when I use setNeedsDisplay,as below:
when I comment out [cell setNeedsDisplay]; then the text of label is display well. But the index of each user is not display right as I want.Here is my code
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
if(!dbManager)
dbManager = [DBManager sharedInstant];
UIBarButtonItem *btnAdd = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:#selector(showAdd)];
self.navigationItem.rightBarButtonItem = btnAdd;
UIBarButtonItem *btnFilter = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch target:self action:#selector(showFilter)];
self.navigationItem.leftBarButtonItem = btnFilter;
[[DBManager sharedInstant] setDelegate:self];
self.collectionView.dataSource = self;
self.collectionView.delegate = self;
[self.collectionView setBackgroundColor:[UIColor clearColor]];
[self.collectionView registerClass:[UserCollectionItemView class] forCellWithReuseIdentifier:#"UserCollectionItemView"];
cells = [[NSMutableArray alloc] init];
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
if (!dbManager.synchronized) {
[datasource removeAllObjects];
datasource = nil;
if (contactType == ContactTypeCustomer)
[dbManager requestData:kDbCustomers predicate:nil target:self];
else if (contactType == ContactTypeSuppplier)
[dbManager requestData:kDbSuppliers predicate:nil target:self];
}
[self setLayout];
}
and for collectionview:
#pragma mark
#pragma UICollectionDelegate
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)cv numberOfItemsInSection:(NSInteger)section
{
return [datasource count];
}
- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
{
[cells addObject:cell];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UserCollectionItemView *cell;
// if([cells count])
// {
// cell = [cells lastObject];
// [cells removeLastObject];
// }
// else
cell = [cv dequeueReusableCellWithReuseIdentifier:#"UserCollectionItemView" forIndexPath:indexPath];
if (contactType == ContactTypeCustomer) {
POSCustomer *customer = [datasource objectAtIndex:indexPath.item];
cell.displayname = customer.CompanyName;
}
else if (contactType == ContactTypeSuppplier){
POSSupplier *supplier = [datasource objectAtIndex:indexPath.item];
cell.displayname = supplier.CompanyName;
}
cell.backgroundColor = [UIColor clearColor];
[cell setNeedsDisplay];
return cell;
}
- (void)collectionView:(UICollectionView *)cv didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
dbManager.synchronized = YES;
if (contactType == ContactTypeCustomer) {
POSCustomer *customers = [datasource objectAtIndex:indexPath.item];
[self showEditCustomer:customers];
}
else if (contactType == ContactTypeSuppplier){
POSSupplier *suppliers = [datasource objectAtIndex:indexPath.item];
[self showEditSupplier:suppliers];
}
}
-(void)showEditCustomer:(POSCustomer *)customer{
ContactFormViewController *form = [[ContactFormViewController alloc] initWithNibName:#"ContactFormViewController" bundle:nil];
[form setContactType:ContactTypeCustomer];
form.posCustomer = customer;
[self.navigationController pushViewController:form animated:YES];
}
-(void)showEditSupplier:(POSSupplier *)supplier{
ContactFormViewController *form = [[ContactFormViewController alloc] initWithNibName:#"ContactFormViewController" bundle:nil];
[form setContactType:ContactTypeSuppplier];
form.posSupplier = supplier;
[self.navigationController pushViewController:form animated:YES];
}
#pragma mark
#pragma DBDelegate
- (void)requestDataCompleted:(NSMutableArray *)results
{
datasource = results;
[self.collectionView reloadData];
}
and here is for custom collectionview:
#synthesize displayname;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
- (void)drawRect:(CGRect)rect
{
CGRect frame = self.contentView.frame;
UIView *view = [[UIView alloc] initWithFrame:frame];
view.layer.borderWidth = 0.5;
[view.layer setBorderColor:[UIColor colorWithRed:0.3 green:0.6 blue:0.2 alpha:1].CGColor];
view.layer.cornerRadius = 5;
[view setBackgroundColor:[UIColor colorWithRed:0.3 green:0.6 blue:0.2 alpha:0.3]];
UIImageView *avatarView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 10, frame.size.width, rect.size.width)];
[avatarView setBackgroundColor:[UIColor clearColor]];
[avatarView setImage:[UIImage imageNamed:#"users_icon"]];
[view addSubview:avatarView];
UILabel *displayName = [[UILabel alloc] initWithFrame:CGRectMake(3, frame.size.width - 10, rect.size.width - 6, 50)];
displayName.numberOfLines = 2;
displayName.text = displayname;
[displayName setFont:[UIFont fontWithName:#"Arial" size:12]];
displayName.textAlignment = NSTextAlignmentCenter;
[displayName setTextColor:[UIColor colorWithRed:0.3 green:0.6 blue:0.2 alpha:1]];
[view addSubview:displayName];
[self.contentView addSubview:view];
}
Thanks for any helps.

Answer 1

Because of this line [self.contentView addSubview:view];, It've added multiple times because setNeedDisplay will call drawRect: every time. To avoid this, try below..
UIView *view = [[UIView alloc] initWithFrame:frame];
view.tag = SomeTagValue;
.
.
.
.
UIView *preView = [self.contentView viewWithTag:SomeTagValue];
[preView removeFromSuperview];
[self.contentView addSubview:view];