Using Xcode 4.6, I am trying to display a typical UITableView with its cells with subtitles.
If I am not wrong, the code is this:
- (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];
}
Test *myTest = [self listTests][indexPath.row];
cell.textLabel.text = [myTest name];
UIFont *cellFont = [UIFont systemFontOfSize:16.0];
cell.textLabel.font = cellFont;
UIFont *detailFont = [UIFont systemFontOfSize:12.0];
NSMutableString *detailText = [NSMutableString stringWithFormat:#"%d", [myTest numQuestions]];
[detailText appendString:#" preguntas."];
cell.detailTextLabel.text = detailText;
cell.detailTextLabel.font = detailFont;
return cell;
}
For some reason, it never passes through this line of code:
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
so the cell is never initialized with UITableViewCellStyleSubtitle.
It is somehow getting ALWAYS FROM THE BEGINING a valid cell when doing [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
What can I be doing wrong?
It is really weard. I always use this code and it normally works. What else can I be doing wrong somewhere else?
This happens when your cell is defined using a storyboard prototype. In this case the reusable cells are pre-created using the initWithCoder: method, so if (cell == nil) never gets hit. See this question for more information.
Since it appears that you would like to use a cell with a standard style, changing the table to not use a storyboard prototype or setting the prototype to "Subtitle" should fix this problem.
Related
I'm working on an iOS project .I created an UITableView to display a list of drones . Everything works fine but I noticed that there is a bug when I click on the cell to display the details of the drone . As u can see in the images below.
When the tableView get loded
When clicked on cell
and this my code when I select a cell :
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *_storyboardName = #"Main";
UIStoryboard *_storyboard = [UIStoryboard storyboardWithName:_storyboardName bundle: nil];
DroneDetailsViewController *detailsVC = [_storyboard instantiateViewControllerWithIdentifier:#"DroneDetailsViewController"];
detailsVC.droneObj = [drones objectAtIndex:indexPath.row];
[self.navigationController pushViewController:detailsVC animated:YES];
[detailsVC.navigationController setNavigationBarHidden:NO animated:YES];
}
This my code for cellForRowAtIndexPath :
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"drone";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
DroneObject *droneObjDisplay = nil;
droneObjDisplay = [drones objectAtIndex:indexPath.row];
NSData *data = [[NSData alloc]initWithBase64EncodedString:droneObjDisplay.modelMSide options:NSDataBase64DecodingIgnoreUnknownCharacters];
[self initCellWithComponents:cell :data :droneObjDisplay.modelName :droneObjDisplay.modelNumber];
return cell;
}
and this the initCelWithComponents :
- (void)initCellWithComponents :(UITableViewCell *)cell :(NSData *)dataImage :(NSString *)title :(NSString *)subTitle {
UIView *viewCell = [[UIView alloc] initWithFrame:CGRectMake(VIEW_MARGIN, VIEW_MARGIN, widthtScreen-20, VIEW_IMAGE_HEIGHT)];
viewCell.layer.borderColor = [UIColor colorWithHexString:NSLocalizedString(#"border_color", nil)].CGColor;
viewCell.backgroundColor = [UIColor whiteColor];
viewCell.layer.borderWidth = 0.5f;
UIImageView *image = [[UIImageView alloc]initWithFrame:CGRectMake(VIEW_MARGIN,VIEW_MARGIN, VIEW_IMAGE_HEIGHT-(2*VIEW_MARGIN),VIEW_IMAGE_HEIGHT-(2*VIEW_MARGIN))];
image.image=[UIImage imageWithData:dataImage];
[viewCell addSubview:image];
UILabel *titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(image.frame.size.width+2*VIEW_MARGIN, VIEW_MARGIN, viewCell.frame.size.width-(VIEW_IMAGE_HEIGHT-(4*VIEW_MARGIN)), 21)];
titleLabel.text = title;
titleLabel.textColor = [UIColor blackColor];
[titleLabel setFont:[UIFont systemFontOfSize:15]];
[viewCell addSubview:titleLabel];
UILabel *subTitleLabel = [[UILabel alloc]initWithFrame:CGRectMake(image.frame.size.width+2*VIEW_MARGIN, 3*VIEW_MARGIN, viewCell.frame.size.width-(VIEW_IMAGE_HEIGHT-(4*VIEW_MARGIN)), 21)];
subTitleLabel.text = subTitle;
subTitleLabel.textColor = [UIColor blackColor];
[subTitleLabel setFont:[UIFont systemFontOfSize:13]];
[viewCell addSubview:subTitleLabel];
cell.contentView.backgroundColor = [UIColor colorWithHexString:NSLocalizedString(#"gray_background", nil)];
[cell.contentView addSubview:viewCell];
}
any ideas how to fix that ?!
Your cell's style is UITableViewCellStyleSubtitle and you also adding title and subtitle label manually also.
If you are using cell's style as UITableViewCellStyleSubtitle then you can directly use
cell.textLabel.text = #"your title label's text";
cell.detailTextLabel.text = #"your detail label's text";
If you will add another label then it will creates duplicate!!!!
Since you are initialising UIView and UILabel in method inside cellForRowAtIndexPath and adding them as subview, these controls are being added to your cell each time cell is reloaded. Below code identifies each cell with a unique identifier and loads the cell only if that particular cell is not available in UITableView.
I have written droneObjDisplay.droneId to uniquely identify cell, you can write anything for droneObjDisplay.__ that is unique identifier of your object.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
DroneObject *droneObjDisplay = nil;
droneObjDisplay = [drones objectAtIndex:indexPath.row];
NSString *CellIdentifier = [NSString stringWithFormat:#"drone_%d", droneObjDisplay.droneId];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
NSData *data = [[NSData alloc]initWithBase64EncodedString:droneObjDisplay.modelMSide options:NSDataBase64DecodingIgnoreUnknownCharacters];
[self initCellWithComponents:cell :data :droneObjDisplay.modelName :droneObjDisplay.modelNumber];
}
return cell;
}
Hope it helps.
The TableViewCell could be designed and used by either one of the following ways,
If you are using the storyboard then you can simply design the prototype cell on the TableView on storyboard itself and then giving an identifier to the cell. If you are using this way then add the component on the storyboard only and give tag to each component to access it in the code if you are not subclassing the UITableViewCell, and dequeue the cell as below,
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
UILabel *labelValue = (UILabel*) [cell viewWithTag:10];
Design the TableViewCell on the storyboard as you did in 1 way and then simply create a subclass of UITableViewCell class and set that class as a Custom Class of the cell by selecting the cell on storyboard, this way you can create the outlet of each component in the cell and you do not need to access the component by the tags. Below is the code to dequeue the cell,
CellSubClassed *cell = (CellSubClassed*)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
cell.labelXYZ.text = arrayDataSource[indexPath.row][#"key"];
This is the old way before storyboard was introduced, Create subclass of UITableView cell and create a xib file with the same name you give to UiTableViewCell subclass, create the outlets of component you want to access. Below is the code to dequeue cell,
NSArray *nib;
static NSString *strNibName = #"CustomCell";
nib = [[NSBundle mainBundle] loadNibNamed:strNibName owner:self options:nil];
CustomCell *cell = [nib objectAtIndex:0];
cell.imageView.image = arrayDataSource[indexPath.row];
The last way is using TableView's default cells, just create the tableView on storyboard/xib and dequeue the cell as below,
static NSString *cellIdentifier = #"cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: cellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
cell.textLabel.text = #"xyz";
The default tableView cell styles are,
UITableViewCellStyleDefault
UITableViewCellStyleSubtitle
UITableViewCellStyleValue1
UITableViewCellStyleValue2
You can read about more on Apple Developer docs here.
So in your case you are mixing the two ways of dequeuing the cell, if you want to add the component manually as you did and you don't want to design the component on the storyboard or Xib then you just create the subclass of UITableView cell and then create the component in the awakeFromNib method and dequeue the cell as explained in 3 way.
Hope it helps you.
Ok finally, after getting your answers guys , I created a Custom Cell a subclass of UITableViewCell and I added all my components there . The main problem was how I will call it without UI (storyboard or xib ) just by code .
So after the creation of the custom cell I added this line to my viewdidload :
[self.tableView registerClass:[CustomCellTableViewCell class] forCellReuseIdentifier:#"CustomCellTableViewCell"];
then in the cellForRowAtIndexPath I just added the custom cell :
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
DroneObject *droneObjDisplay = nil;
droneObjDisplay = [drones objectAtIndex:indexPath.row];
static NSString *identifier = #"CustomCellTableViewCell";
CustomCellTableViewCell *cell = (CustomCellTableViewCell *)[tableView dequeueReusableCellWithIdentifier:identifier];
NSData *data = [[NSData alloc]initWithBase64EncodedString:droneObjDisplay.modelMSide options:NSDataBase64DecodingIgnoreUnknownCharacters];
cell.image.image = [UIImage imageWithData:data];
cell.titleLabel.text = droneObjDisplay.modelName;
cell.subTitleLabel.text = droneObjDisplay.modelNumber;
return cell;
}
Any help please!! I am trying to show title and details, but details do not display(blank).
-(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] ;
}
NSString * theCell = [NSString stringWithFormat:#"From %# to %# at %#", [flights valueForKey:#"depAirport"],[flights valueForKey:#"destAirport"],[flights valueForKey:#"depTime"]];
NSLog(#"the %#", theCell);
// Configure the cell...
// Configure the cell...
cell.textLabel.font = [UIFont fontWithName:#"Helvetica" size:12];
cell.textLabel.lineBreakMode = UILineBreakModeWordWrap;
cell.textLabel.numberOfLines = 0;
cell.textLabel.textColor =[UIColor blackColor];
cell.textLabel.text = [[flights objectAtIndex:[indexPath row]] valueForKey:#"flight_ID"];
cell.detailTextLabel.text = theCell;
return cell;
}
Any help would be appreciate!!
If you are using a storyboard, your cell not become nil. That means cell is always returned from dequeue method. So your cell initialization code never get initialized and the style doesn't change to UITableViewCellStyleSubtitle. Therefore detail text label doesnt exist.
So you have to change the prototype in the storyboard to have the subtitle style.
What UITableViewCellStyle are you using? UITableViewCellStyleDefault will not work.
I'm having a bit of difficulty understanding what is going wrong and how to fix this.
-(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];
NSUInteger row = [indexPath row];
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
cell.selectionStyle = UITableViewCellSelectionStyleBlue;
UILabel *where = [[UILabel alloc] initWithFrame:CGRectMake(88.0, 0.0, 155.0, 22.0)];
where.text = [delegate.destinationArray1 objectAtIndex:row];
where.font = [UIFont fontWithName:#"Helvetica" size:12.0];
where.textColor = [UIColor blueColor];
[cell.contentView addSubview:where];
return cell;
}
This doesn't work properly but this does:
-(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];
}
NSUInteger row = [indexPath row];
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
cell.selectionStyle = UITableViewCellSelectionStyleBlue;
UILabel *where = [[UILabel alloc] initWithFrame:CGRectMake(88.0, 0.0, 155.0, 22.0)];
where.text = [delegate.destinationArray1 objectAtIndex:row];
where.font = [UIFont fontWithName:#"Helvetica" size:12.0];
where.textColor = [UIColor blueColor];
[cell.contentView addSubview:where];
return cell;
}
They both get populated by "delegate.destinationArray1" but when all the code is inside the curly braces of
if(cell == nil)
the list gets unordered and repeats cells and misses some out. I can't use the latter way as it creates a MASSIVE memory leak when scrolling.
Any ideas?
I did the exact same thing when I started using UITableViews. The reason for the memory leak is that in the second implementation (the one that works) you are actually creating every cell, every single time. Let me try to explain a bit more.
You never want to set content of a cell between the (cell == nil). The reason for this is the reuseIdentifier. If the table needs to display a new cell it will grab one and see if it has already been alloced/inited. If it has it will just use it. If that is the case the content will already be set in the cell you grabbed and you are not telling it to set it any differently.
between the (cell == nil) only create and establish the view. Not the content. All content should be set after. So then no matter what cell it grabs it can always set the content. So this is what you want:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(!cell) // or (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
cell.selectionStyle = UITableViewCellSelectionStyleBlue;
UILabel *where = [[UILabel alloc] initWithFrame:CGRectMake(88.0, 0.0, 155.0, 22.0)];
where.font = [UIFont fontWithName:#"Helvetica" size:12.0];
where.textColor = [UIColor blueColor];
where.tag = 1;
[cell addSubview:where];
}
NSUInteger row = indexPath.row;
UILabel *where = [cell viewWithTag:1];
where.text = [delegate.destinationArray1 objectAtIndex:row];
return cell;
}
I just coded this in StackoverFlow so sorry if there are any small syntax errors.
The cell object is reused or created by the first statement. After checking cell for nil and creating a cell, you must not create another cell.
So delete the line
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
which comes after
NSUInteger row = [indexPath row];
and you'll work with the correct cell object.
When the tableview reuses cells it is based on the CellIdentifier. The tableview doesn't care what attributes you've set on the cell. In the first case the reuse it happening and it recognizes a cell it can use but that cell has the wrong information on it.
What I do is subclass UITableViewCell and do all the work inside of that class. Here is a quick snippet
#implementation AlertCell
//Custom init method
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier withHeight:(float)height {
//Whatever you need to do
}
//Place the views
- (void)layoutSubviews {
}
//Custom Setter method
- (void)setAlert:(CWAlert *)incomingAlert withAssets:(NSDictionary *)assets {
}
#end
Then you do something like this
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier;
CWAlertCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell) {
cell = [[AlertCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier withHeight:[self convertAssetsLengthToCellHeight:assetsLength]];
UIView *selectedView = [[UIView alloc] init];
selectedView.backgroundColor = [UIColor colorWithHexString:#"F6F6F6"];
cell.selectedBackgroundView = selectedView;
}
NSDictionary *alertInfo = [AlertCell getNeededCellAssets:alert];
[cell setAlert:alert withAssets:alertInfo];
return cell;
}
I can show more code from the subclass if needed.
I'm having an issue in trying to display info in a cell, one on the left and one on the right. I'm aware using initWithStyle with UITableViewCellStyleSubtitle. I use this but it doesn't seem to work.
Here is some sample code:
- (UITableViewCell *)tableView:(UITableView *)ltableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Account Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:Cellidentifier];
}
Accounts *account = [self.fetchedResultsController objectAtIndexPath];
cell.textLabel.text = account.name;
cell.detailTextLabel.text = #"Price";
return cell;
}
I can display cell.textLabel.text just fine, however I cannot get the simple "Price" to be displayed. I've tried different things, such as setting the font size of cell.detailTextLabel.
I've also tried UITableViewCellStyleValue1 as some had suggested in older posts.
Threw NSLog after setting to "Price", shows cell.detailTextLabel as null.
Not sure what I'm doing wrong.
Edit: I found this: cell.detailTextLabel.text is NULL
If I remove if (cell == nil) it works...
That check should be in place, so how do you make it work when using the different styles?
When using storyboards and prototype cells, a cell is always returned from the dequeue method (assuming a prototype with that identifier exists). This means you never get into the (cell == nil) block.
In your case the prototype cell is not defined in the storyboard with the subtitle style, so a subtitled cell is never used, and the detail text label does not exist. Change the prototype in the storyboard to have the subtitle style.
Remove all your code just once you try these lines only and check this will work or not.
-(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]
autorelease];
}
cell.textLabel.text=[Array objectAtIndex:indexPath.row];
cell.detailTextLabel.text=#"Price";
return cell;
}
I see the problem: in your method name, the UITableView variable is named ltableView, not tableView. Change it to tableView.
cell.detailTextLable.text should be cell.detailTextLabel.text. It looks like a simple mis-spelling of label.
All the answers mentioned here are really a workaround i.e. using storyboard.
Here is a way to do it only in code.
Basically instead of registering the identifier for the cell in viewDidLoad do it only once in cellForRowAtIndexPath: method. Also reset cell registered in viewDidLoad __sCellRegistered = 0;
static int _sCellRegistered = 0;
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = nil;
if (__sCellRegistered == 0) {
__sCellRegistered = 1;
NSLog(#"register cell");
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:#"CellIdentifier"];
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"CellIdentifier"];
};
if (!cell) {
NSLog(#"dequeue");
cell = [tableView dequeueReusableCellWithIdentifier:#"CellIdentifier" forIndexPath:indexPath];
}
For each time UITableview is scrolled, there is a memory leak of 48 bytes.
Responsible library : libsystem_c.dylib
Responsible frame : strdup.
This is observed only on iOS 5.1 and not on earlier versions.
Did anyone else faced the same? Is this a bug in iOS 5.1?
Code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath(NSIndexPath *)indexPath
{
NSString *cellIdentifier = [[NSString alloc] initWithString:#"fontSelectionCell"];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
[cellIdentifier release];
if (cell == nil)
{
cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
}
cell.textLabel.text = [fontNameList objectAtIndex:[indexPath row]];
cell.selectionStyle =UITableViewCellSelectionStyleGray;
cell.textLabel.font = [UIFont systemFontOfSize:17.0];
if ([fontName isEqualToString:cell.textLabel.text])
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
cell.textLabel.textColor = [UIColor blueColor];
}
else
{
cell.accessoryType = UITableViewCellAccessoryNone;
cell.textLabel.textColor = [UIColor blackColor];
}
return cell;
}
It could be due to the way you are handling the cell identifier. I'm actually surprised it does not crash for you, since you release cellIndentifier but then reference it when creating a new cell (i.e. when a cell wasn't return for reuse from dequeueReusableCellWithIdentifier).
The standard/accepted way to use a cell identifier is to use a static (because it won't ever change, and it will only be alloc-ed once and not potentially 100s of times since cellForRowAtIndexPath is called constantly when scrolling a table). This would make your code much more efficient.
i.e.
- (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"fontSelectionCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease];
}
...
}
Could you try changing cellIdentifier and see if you still get the leak?
I think you are having this issue that was already report on iOS 5.1. I am having that myself too. At the moment I wasn't able to find the link in apple's forums concerning this issue.