Recently I noticed that when we creates a new Class template, (Xcode -> File -> New -> File) which is a subclass of UITableViewController implementation is partial in cellForRowAtIndexPath method. I pasted the method below.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
return cell;
}
I think statements like (which is missing),
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
is must in implementation. Is this a bug or something else ?
You don't need to create a cell if you are registering a cell in your table view with the method registerNib:forCellReuseIdentifier: or registerClass:forCellReuseIdentifier: or creating a cell within your table view in a xib or storyboard.
Related
My table simply has row with a UIImageView. When I assign the image directly like the below mentioned way
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *identifier = #"cellidentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier forIndexPath:indexPath];
// Configure the cell...
cell.imageView.image = [self.backgroundImages objectAtIndex:indexPath.row];
return cell;
}
It returns error:
unable to dequeue a cell with identifier cellidentifier - must
register a nib or a class for the identifier or connect a prototype
cell in a storyboard'.
So I wonder is there a way to ignore to register a nib or a class for UITableViewCell in order to shorten the code in this case?
If you are using custom class for your cell then you should register the class (in viewDidLoad),use registerNib:forCellWithReuseIdentifier: if the cell is made in a xib file.
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"Cell"];
else write cellForRowAtIndexPath tableView delegate as follows:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
//Configure cell
return cell;
}
You just need to add one line in your viewDidLoad to resolve the error
- (void)viewDidLoad
{
[super viewDidLoad];
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"cellidentifier"];
}
Put your cell identifier in storyboard as below screenshot.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Songcell"; // copy this identifier and paste it into your storyboard tableviewcell indetifier
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
UIImageView *IMAGEVIEWNAME = (UIImageView*)[cell viewWithTag:YOUR_TAG]; // give tag to your imageview from storyboard and access it here
IMAGEVIEWNAME.image = [UIImage imageNamed:#"YOURIMAGENAME"];
return cell;
}
Give same name in your storyboard tableviewcell identifier
cellidentifier with this name . i just give my cell identifier songcell.
I am using a table view inside custom cell.The below code specifies the table inside custom cell.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"commnetCell";
commnetCell *cell = (commnetCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
// Configure Cell
[cell.lbl_comment setText:#"kool"];
return cell;
}
here cell returns nill.I have set the delegate and datasource.
You have to allocate the cell if there is none in the reuse queue.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:CellIdentifier];
}
// Configure the cell.
return cell;
}
Alternatively, you can create a prototype in the storyboard or register a custom cell class. Then, you don't have to allocate it on your own. It will be created for you when you request it using the dequeueReusableCellWithIdentifier method.
The dequeueReusableCellWithIdentifier: will always return a cell if you have called registerClass: with the corresponding identifier.
I simply don't understand how to fix this from what's out there.
It's fairly simple, I add a UITextField to my UITableViewCell. The user may type in it, then after scrolling it out and back into view the contents will be reset back to its default status.
This is to do with re-using old cells with dequeueReusableCellWithIdentifier right? I just don't understand how to fix it!
Here is my code:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
//Stop repeating cell contents
else for (UIView *view in cell.contentView.subviews) [view removeFromSuperview];
//Add cell subviews here...
}
You don't have to remove the cell contents once it is initialized they are never recreated, they are reused so your code should look like below
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
}
And I assume you want to have some controls onto your cell, in this case you can try using CustomCell which creates all the subviews on initializations.
Usually, all your initializations should be in
if (!cell)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
//ALL INITS
}
and outside it you should update the values you added into the cell..
You need to set the inputted text back to the textfield, currently with reuse of cells, the textfield clears out the contents. You could try to store the textfield input in an nsstring property and in your cellforrow method, set the textfield text as that string, if the string has a valid value. That way, even on scrolling, the textfield will only display the user input that was stored into the nsstring property from the textfield.
Before You follow my Answer i want to tell you that following code is bad for memory management because it will create new cell for each rows of UITableView, so be careful for it.
But it is better to use, When UITableView Have Limited rows (about 50-100 may be ) then following code is helpful in your case. Use it, if it is suitable for you.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier = [NSString stringWithFormat:#"S%1dR%1d",indexPath.section,indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil)
{
cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
/// Put your code here.
}
/// Put your code here.
return cell;
}
If you have limited rows then this is best code for you.
i was following this torturial:
http://www.raywenderlich.com/32283/core-graphics-tutorial-lines-rectangles-and-gradients
It covers customization of dynamic table cells, i need to do it with static table cells.
I have given every cell the identifier "Cell", as he does in the tutorial, i then subclassed the table view controller and implemented this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString * CellIdentifier = #"Cell";
UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
// START NEW
if (![cell.backgroundView isKindOfClass:[CostumCellBackground class]]) {
cell.backgroundView = [[CostumCellBackground alloc] init];
}
if (![cell.selectedBackgroundView isKindOfClass:[CostumCellBackground class]]) {
cell.selectedBackgroundView = [[CostumCellBackground alloc] init];
}
// END NEW
cell.textLabel.backgroundColor = [UIColor clearColor]; // NEW
return cell;
}
CostumCellBackground draws the rect.
I am getting the error "UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:
As far as i understand UITableView is looped for every Cell in the storyboard, and it is supposed to return cell.
So, whats going on here and why does the cell return nil, or doesnt return at all ?
The only difference is that they are static tables, and not prototypes.
If you are using Storyboards and iOS6 and your view controller is a UITableViewController, you will always get a cell if your cell identifier is present in your storyboard. Checking for cel == nil is the old way to do it.
Are you sure you have a custom cell in your storyboard with the "Cell" identifier?
Also, use this:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
If you look in the UITableView.h file you will find:
// newer dequeue method guarantees a cell is returned and resized properly, assuming identifier is registered
- (id)dequeueReusableCellWithIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);
Where is you create your cell ??
You should add after:
UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
such code (or something another initializer):
if (cell == nil) {
cell = [[UITableViewCell alloc] init];
}
Try this at the beginning of your method:
- (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
];
}
I am using a TableView xib and all the delegates and datasource seem to be running fine.
If I set self.textLabel.text, it displays the generic number of tableviews correctly, but I need to have my custom TableViewCell showing.
I created a HistoryCell.xib that has just a tableviewcell in it.
I created a UITableViewCell class "HistoryCell.h/HistoryCell.m" and it is set as the file owner of HistoryCell.xib.
I connected the UILabels to the HistoryCell.h
UILabel statusLabel
UILabel nameLabel
UILabel timeLabel
In my main ViewController class int he cellForRowAtIndexPath
I am putting in
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"historyCellType";
HistoryCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[HistoryCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
cell.nameLabel.text = #"Donald Duck";
return cell;
}
What am I doing wrong?
Thanks!
You should register the nib like this (probably in viewDidLoad):
[self.tableView registerNib:[UINib nibWithNibName:#"HistoryCell" bundle:nil ] forCellReuseIdentifier:#"historyCellType"];
Then in your cellForRowAtIndexPath method, use this new way where you don't need the if cell == nil clause:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
HistoryCell *cell = [tableView dequeueReusableCellWithIdentifier:#"historyCellType" forIndexPath:indexPath];
cell.nameLabel.text = #"Donald Duck";
return cell;
}
You need to deserialize the actual XIB data:
HistoryCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSArray *cellnib = [[NSBundle mainBundle] loadNibNamed:#"HistoryXIBName" owner:self options:nil];
cell = (HistoryCell *)[cellnib objectAtIndex:0];
}
Otherwise it's just using a "Default" cell.
EDIT: Also, if you are using storyboards, dynamic cell prototypes remove the need to create cells from NIB files (in case that's an option for you.)
EDIT The 2nd:
You can try this as well (this assumes you are using ARC):
HistoryCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
HistoryCell *aNewCell = [[HistoryCell alloc] initWithNibName:#"HistoryXIBName" bundle:nil];
cell = (HistoryCell *)*aNewCell.view;
}
There's another method using outlets to your cell in the containing view's XIB file that's a bit more involved that I used to use when iOS4 was current. If the edited version isn't' working for you, I'll dig out an old project and remember how I did it.
When you use tableViewCell with xib, while instantiation load from xib.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"historyCellType";
HistoryCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[NSBundle mainBundle]loadNibNamed:#"HistoryCell"
owner:nil
options:nil]lastObject];
}
cell.nameLabel.text = #"Donald Duck";
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellidentifier=#"cell1";
customcell *cell =
(customcell*)[tableView dequeueReusableCellWithIdentifier:cellidentifier];
if (cell==nil) {
[tableView registerNib:[UINib nibWithNibName:#"Customcell" bundle:nil]
forCellReuseIdentifier:cellidentifier];
cell =
(customcell*)[tableView dequeueReusableCellWithIdentifier:cellidentifier
forIndexPath:[NSIndexPath indexPathForItem:indexPath.row
inSection:indexPath.section]];
}
return cell;
}