My custom cell contains the toggling badges and a label inside that badge (both in xib). Then how can I reuse the cell? If I make the cell.imgBadgeImageView.image = nil and cell.lblBadgeLabel.Text = nil in prepareForReuse method of custom cell both of them will disappear from all the remaining cells (as we are reusing the cells).
Do I need to add the badge and label inside it as a subview to the cell from code? If I do so how can I access the cell badge image view and badge label. I need to access these two because there is a nice animation (for the image view) and text change (for the label).
I am currently making all the cells nil which are not in the view using this delegate method:
-(void)tableView:(UITableView *)tableView didEndDisplayingCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
if ([tableView.indexPathsForVisibleRows indexOfObject:indexPath] == NSNotFound){
VBMerchantDealCell *cell = (VBMerchantDealCell *)[tableView cellForRowAtIndexPath:indexPath];
cell = nil;
}
}
I understand that you want to reuse the cell. I don't know if the approach that you are taking is right, but I do it the way Apple has told me to do it.
a. Set the reuse identifier in the xib. Say "MyCustomCell".
b. Register the cell after your table view allocation using:
self.cellNib = [UINib nibWithNibName:#"MyCustomCell" bundle:nil];
[self.tableView registerNib:self.cellNib forCellReuseIdentifier:#"CustomCell"];
c. Get the cell at your ``cellForRowAtIndexPath` using:
NSString *identifier = #"MyCustomCell";
UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier];
I'm newbie in IOS and again i face another issue. How can i prevent data vanish from a table cell when i scroll a tableview.
I'm using the code below to load data on the table...Works fine but the data disappear when table cell go in not visible to the screen.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
list = [self.listas objectAtIndex:[indexPath row]];
static NSString *CellIdentifier = #"drop";
item_drop *cell = (item_drop*) [tabela_listas dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"item_drop" owner:self options:nil];
cell = [nib objectAtIndex:0];
}
cell.texto_drop.text = list.nome_lista;
return cell;
}
In android i used a holder to do it. There is anything similiar on IOS?
Since you are using reusable cells of a custom subclass of UITableViewCell, make sure you register the cell identifier in the UITableView, associating it to your custom cell type. i.e:
[yourTableView registerClass:[item_drop class] forCellReuseIdentifier:#"drop"];
You typically do this when you configure subviews in the UIViewController that controls the view your UITableView is a part of, in viewDidLoad.
With that in place, you should never hit the code inside if (cell == nil).
I am making a bookmarks page for my web browser and the problem is that everytime I add a new object, I have to set the properties since I created a custom cell (I must set the text of two labels) and so I need a way to only edit the newly added object...I'm familiar with indexes but not able to come up with any solutions to this problem...For example when I bookmark the first page its fine, but once I bookmark 2 pages the 2 cells are the exact same...Any Ideas?
Heres My Code:
// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"CustomCell";
CustomCell *cell = (CustomCell*)
[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"CustomCell" owner:nil options:nil];
cell = (CustomCell *) [nib objectAtIndex:0];
}
// Set up the cell...
NSString *theTitle=[webView stringByEvaluatingJavaScriptFromString:#"document.title"];
NSString *currentURL = webView.request.URL.absoluteString;
cell.websiteTitle.text = theTitle;
cell.websiteURL.text = currentURL;
universalURL = currentURL;
return cell;
}
When setting up the cell I need to point to the newest cell!
Thank You In Advance!
Your approach cannot work. You cannot use the cells as the store for the titles and URLs, because cells are reused (and because it is bad design). A table view allocates only cells for the visible rows and reuses a cell for a different row when you scroll the table view.
Instead you should store the titles and URLs in a separated data source, for example an NSMutableArray *bookmarks where each item in the array is a NSDictionary with "title" and "URL" keys.
To add a bookmark to your table, you just append a new entry to the array and call reloadData on the table view.
The tableView:cellForRowAtIndexPath: method can then use the bookmarks array with the row number indexPath.row to fill all elements of the cell.
I have a tableView with sections, which could be opened and closed. So, when I tap on a section to open it, it is getting filled up with cells and -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) get called exactly as much times as I provided in -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section.
Is that correct? Shouldn't it be just number of visible cells?
Because in my case I have bad situation: I have a lot of custom cells (50~100 cells) and calling -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) for each cell slows down the opening of a section, cause each time reading from nib is performed and cell content is being populated with image.
I've check visibility of cell inside -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) like this:
if ([[self.tableView indexPathsForVisibleRows] containsObject:indexPath])
NSLog(#"visible %#", indexPath);
and it shows that from out of 45 cells, only 6 or 7 are visible. Others are out of visible area. But creating cells still performed.
Here is the code:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"IVCell";
IVCamera *camera = [server.cameras objectAtIndex:indexPath.row];
IVServerListViewCell *cell = (IVServerListViewCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:#"IVServerListCell" owner:self options:nil];
cell = (IVServerListViewCell*)_tableViewCell;
self.tableViewCell = nil;
}
[cell textLabel].text = camera.cameraName;
cell.preview = camera.preview;
cell.userData = camera;
cell.isEnabled = (server.isInactive)?NO:camera.isOnline;
return cell;
}
Is it still correct? Or am I missing something?
increase your
estimatedRowHeight of UITableview.
Well, I somehow dealt with my problem. Here are my ideas and thoughts how I came to the solution. Maybe it could be helpful to somebody.
I've instructed memory allocations and call stack using Instruments during opening section events. It showed me, that the majority of time is spent on loading cell from nib file.
Firstly, that I've done was reducing the size of nib file, i.e. minimizing the number of views used in custom tableview cell (now its only 2 views and 2 labels, instead of 6 views, 2 images and 2 labels before). It gave me some improve in cells loading. Apple documentation suggests to use as few as possible views and do not use transparency. So be attentive to these suggestions.
Secondly, as I discovered earlier, that not all cell are visible which are created by -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *), I decided to reduce somehow the number of loadings new cells from nib file. To achieve this, I've came to simple idea: return blank default cells for invisible rows, while load custom cells from nib for visible ones. Here is the piece of code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if ([self index:indexPath isInvisibleInTableView:tableView])
return [self getBlankCellForTableView:tableView];
// the rest of the method is the same
...
}
-(BOOL)index:(NSIndexPath*)indexPath isInvisibleInTableView:(UITableView*)tableView
{
NSMutableArray *visibleIndexPaths = [self getExtendedVisibleIndexPathsForTableView:tableView];
return ![visibleIndexPaths containsObject:indexPath];
}
-(UITableViewCell*)getBlankCellForTableView:(UITableView*)tableView
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"IVBlankCell"];
if (!cell)
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"IVBlankCell"] autorelease];
return cell;
}
As you can see, I'm not using just -(NSArray*)indexPathsForVisibleRows method of tableview for detecting visible cells. Instead, I've wrote my own method -(NSMutableArray*)getExtendedVisibleIndexPathsForTableView:(UITableView*)tableView. It was necessary because for some reason, when using -(NSArray*)indexPathsForVisibleRows the cells that are next to the last one visible cell or the cells that are previous to the first one visible cell were created as blank cells and looked like empty cells while scrolling. To overcome this, in -(NSMutableArray*)getExtendedVisibleIndexPathsForTableView: (UITableView*)tableView i'm adding border cells to the visible array cells:
-(NSMutableArray*)getExtendedVisibleIndexPathsForTableView:(UITableView*)tableView{
NSArray *visibleIPs = [tableView indexPathsForVisibleRows];
if (!visibleIPs || ![visibleIPs count])
return [NSMutableArray array];
NSIndexPath *firstVisibleIP = [visibleIPs objectAtIndex:0];
NSIndexPath *lastVisibleIP = [visibleIPs objectAtIndex:[visibleIPs count]-1];
NSIndexPath *prevIndex = ([firstVisibleIP row])?[NSIndexPath indexPathForRow:[firstVisibleIP row]-1 inSection:[firstVisibleIP section]]:nil;
NSIndexPath *nextIndex = [NSIndexPath indexPathForRow:[lastVisibleIP row]+1 inSection:[lastVisibleIP section]];
NSMutableArray *exVisibleIndexPaths = [NSMutableArray arrayWithArray:[tableView indexPathsForVisibleRows]];
if (prevIndex)
[exVisibleIndexPaths addObject:prevIndex];
[exVisibleIndexPaths addObject:nextIndex];
return exVisibleIndexPaths;
}
Thereby, I've reduced the time of opening sections with large number of custom cells, which was proved by Instruments tracing and felt while experiencing the app.
Simply add estimated height for UITableViewCell
Problem In my case was: cellforRowAtIndexPath was getting called array.count number of times, whereas, displayed cells where less than array.count.
To resolve this issue, I have just replaced,
(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
with,
(CGFloat)tableView:(UITableView )tableView estimatedHeightForRowAtIndexPath:(nonnull NSIndexPath )indexPath;
check your tableview size.
may be that your tableview height is very large that it keep loading cells until your cell fills all tableview size..
This seems correct yes. the idea about optimizing the loading itself lies within how "dequeueReusableCellWithIdentifier" works.
if u are loading the image from a remote location this is where u would want to optimize the code. but not from the loading of cells as this looks correct here.
I used some similar technique but since indexPathsForVisibleRows is sorted you don't need to use containsObject. Instead you can just do:
//
// Checks if indexPath is visible in current scroll state, we are expanding bounds by 1
// because the cells that are next to the last one visible or the cells that are previous
// to the first one visible could look empty while scrolling.
//
- (BOOL)isIndexPathVisible:(NSIndexPath *)indexPath
{
NSInteger row = [indexPath row];
NSArray *visible = [self.tableView indexPathsForVisibleRows];
NSInteger count = [visible count];
NSInteger first = (count > 0) ? MAX([visible[0] row] - 1, 0): 0;
NSInteger last = (count > 1) ? [visible[1] row] + 1: first + 2;
return row >= first && row <= last;
}
By the way; this assumes that you are using only one section. It won't work for more than one section.
Adding an else solved my problem.
Where I reseted any changes that were made to the cell.
if (! self.cell) {
self.cell = [[LanguageCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
self.cell.accessoryType = UITableViewCellAccessoryNone;
}
else
{
self.cell.checkImage.image = NO;
}
i have a uitableview in the uiviewcontroller, i made a scrollview in the viewload event.
i am adding it to tableview's first cell. but i scroll the tableview it displays more than one scrollview after 5 cell passed.
here is the code.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"customCell";
DetailCellViewController *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSArray *nibObjects =[[NSBundle mainBundle] loadNibNamed:#"DetailCellView" owner:nil options:nil];
for (id currentObject in nibObjects)
{
if ([currentObject isKindOfClass:[DetailCellViewController class]])
{
cell = (DetailCellViewController *) currentObject;
}
}
}
if (indexPath.row==0) {
[cell.contentView addSubview:scrollView];
}
else {
NSMutableDictionary *dictionary=[catData objectAtIndex:indexPath.row-1];
NSString *title =[dictionary objectForKey:#"title"]];
[cell.catTitle setText:title];
}
return cell;
}
in which event should i add & remove scrollview?
My guess is that you're getting a dequeued UITableViewCell that already contains the UIScrollView. If you really care about separating cell types, I'd recommend setting it up so that you at least have two CellIdentifier strings. (There are times where I've set up a UITableView to handle 4+ different cell types; once you go beyond one cell type, it's pretty much just more of the same.)
My suggested solution: (see explanation below code)
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"bodyCell";
static NSString *HeaderIdentifier = #"headerCell";
UITableViewCell *cell;
// I break this up into 3 sections
// #1. Try to dequeue a cell
// #2. Create a new cell (if needed)
// #3. Set up the cell I've created
// Step 1: Try to dequeue a cell
if ([indexPath section] == 0) {
cell = [tableView dequeueReusableCellWithIdentifier:HeaderIdentifier];
} else {
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
}
// At this point, we may or may not have a cell to use,
// so we check for the cell's value being equal to 'nil'
// and create a new cell if it is
// Step 2: Create a new cell (if needed)
if (cell == nil) {
// Again, here we check for section to determine
// what kind of cell we want
if ([indexPath section] == 0) {
// We have the "header"/first cell
// Option 1
cell = [[ScrollViewTableViewCell alloc] init];
// Option 2 (this assumes you've got a xib named
// ScrollingTableViewCell along with a class property
// named headerCell and have properly wired it up in
// Interface Builder)
[[NSBundle mainBundle] loadNibNamed:#"ScrollingTableViewCell"
owner:self
options:nil];
cell = [self headerCell];
[self setHeaderCell:nil];
} else {
// We have a "body" cell (anything other than the first cell)
// Option 1
cell = [[BodyTableViewCell alloc] init];
// Option 2 (again, assuming you've set things up properly)
[[NSBundle mainBundle] loadNibNamed:#"BodyTableViewCell"
owner:self
options:nil];
cell = [self bodyCell];
[self setBodyCell:nil];
}
}
// At this point, whether dequeued or created
// new, 'cell' should be populated
// Again, we check for section and set up the cell as appropriate
if ([indexPath section] == 0) {
// Set up the header (UIScrollView) cell as appropriate
// This is where you would add the UISCrollView to your cell
// (if you haven't set up the UIScrollView through Interface Builder)
} else {
// Set up the "body" cell as appropriate
}
return cell;
}
NOTE: I HIGHLY recommend using Option 2 above. By far, the best results I've found when using custom/non-standard UITableViewCells is to make my own UITableViewCell subclass and xib to go along with it. Here are the steps for that:
Create a subclass of UITableViewCell (we'll call yours ScrollingTableViewCell.h/.m)
Class forward/import ScrollingTableViewCell into your UITableViewController (or UIViewController that's hosting a UITableView).
Create a class property of type ScrollingTableViewCell (we'll call yours ScrollingCell).
Create a View (New File > User Interface > View) (we'll call yours ScrollingTableViewCell.xib).
Delete the stock view item in the xib and replace it with a UITableViewCell item.
Alternative #4/5
Create an empty Xib.
Add a UITableViewCell item.
VERY IMPORTANT
In the xib, the File's Owner is the ViewController, NOT the UITableViewCell. The cell's class is ScrollingTableViewCell.
In IB, connect the ViewController's ScrollingCell property to the UITableViewCell item.
If you follow the above instructions, you should be able to allocate your cell using Option 2 above and then you can set up your cell in ScrollingTableViewCell.h/.m.