I have tried to create a custom cell that would display a list of items. To achieve this I tried to create a custom cell with UITableView inside it with scroll disabled.
The problem I have with this is when i try to apply changes to the cells in the inner UITableView data just does not get updated and the cell stays as it was. I have tried calling [tableView reloadData], [cell setNeedsDispaly], [cell setNeedsLayout] to no avail.
It seems like the data that has been applied when the cell was initialised persists through any attempts to change it. Though, when I create a breakpoint in cellForRowAtIndexPath: the data does get updated but is not rendered.(e.g. text property of UILabel has new value, but text is old on the screen.)
You need to nil the cell and then reload the table view. For some reason iOS caches table view data and stuff doesn't get updated correctly.
You could try overriding UITableViewCell's prepareForReuse(): in that method you can set all the cell's outlets/properties to nil. You would do this for the cells in the main cell's table view. I am assuming those are custom cells as well and that you have a custom UITableViewCell subclass for them.
Refer [I have two views on one cell, when I click on a cell it will be hidden and one edit form will be expanded on that. How to resolve that? ..check in accepted answer methods ...
[tableView reloadRowsAtIndexPaths:ll withRowAnimation:UITableViewRowAnimationAutomatic] in didSelectRowAtIndexPath
Related
I need to add a subview to TableViewCell when the button in TableViewCell is clicked it should show another tableview as a subview and height of the tableview should be dynamic according to number of cell.
How can I do this?
Above screenshot is taken from a very popular shopping app and I need to do the same in my project.
You can easily achieve this using simple UITableView. For that you need to set all your main categories as your UITableview section and respected sub-categories can be added to respective rowOfSection.
You can use just one table view with UITableViewStyleGrouped style, and set "Men","Women","Kids & Baby" as TableView sections header, keep an boolean value to determine the result of "numberOfRowsInSection:" of each section and reload tableview.
See the below link at github:
https://github.com/OliverLetterer/SLExpandableTableView
This contains the Expandable TableView, which you required. You have to implement SLExpandableTableViewDelegate and SLExpandableTableViewDatasource which contains different method, in which you have to provide inner tableview as well.
Hope this helps you.
You need to do some work on your own I can give the directions that'll give you a way from my point of view :-
Make a Custom cell which you want to expand.
While designing the cell make its height in storyboard like 200 or so according to your need and add all the elements those you want to see when the cell is expanded.
You'll need two delegate methods first -didSelectItemAtIndexPath and second HeightForRowAtIndexPath at index path.
First You need to make sure the user taps on the button or cell that you want to expand , and to achieve that you need to call didSelectItemAtIndexPath.
Once you get your cell Position, in HeightForRowAtIndexPath check the indexpath is equal to your cell's indexpath,if yes then return the exact height(ie:200) of your cell otherwise return the default(ie:70) height of you cell.
Note : In didSelectItemAtIndexPath you need to call to method to update the current cell
[self.tableView beginUpdates];
[self.tableView endUpdates];
My UITableViewCell has a cell template which is created from another nib file. The cell has a UIlabel object. Now, once the UITableView has loaded and the text has been displayed, and if I want to change its value by clicking a button from another cell, How should I do it ?
I have updated the text of the UIlabel but how to show it on the screen? Should I reload the entire table? Kindly let me know if there is any good way to do it.
You can use KVO for this purpose. Each cell observes the model, and when it changes, update some fields.
My setup
I have a UITableViewCell that is in my main storyboard in a UITableViewController. It gets populated with some JSON data pulled from a REST API that will cause each cell to be a variable height. There are UIImageViews, UILabels all of different heights and styles, think Instagram-esque.
My problem
When I scroll to maybe the 5th or 6th cell, then go back up, they start redrawing and overlapping, so text gets mixed, lines get redrawn, etc.
What I've tried
This seems like a common problem on SO, so I've tried several posted solutions. It seems like my issue is probably the same problem as others face, which is, I am calling addSubview on my cell every time it dequeues, but I've tried checking to see if the cell already exists. I came across another post somewhere (sorry, I can't remember where), that suggests that because I am creating this in the storyboard, it is already initialized and if ( !cell ) will already return false, so I don't know how to prevent it from redrawing.
When I try removing the cell from the storyboard, and creating it programmatically, I get an error saying it can't find a cell with my identifier #"Cell".
I've also tried someone's solution of removing all subviews when I dequeue, so I used:
for ( UIView *view in cell.contentView.subviews ) {
if ([view isKindOfClass:[UIView class]]) {
[view removeFromSuperview];
}
}
and it doesn't find anything.
#rdelmar's comment is correct. You shouldn't do what you're doing. Might work, but it's bad form and you don't want to get into bad habits.
First, take advantage of object oriented programming. A cell should be able to configure itself based on the data you ask it to display. The table view shouldn't be designing the cell.
UITableViewCells need to be optimized for speed. Creating and adding subviews is a slow process. It's OK to do it once, but the cell will be reused (a system optimization) and you should just reuse the existing views that were added the first time the cell was created.
For example, you can hide subviews if they're not needed. You might want to do this in -prepareForReuse. You can move them around in -layoutSubviews. Or change the position of subviews in -updateConstraints.
Typically you just want to pass the data to display to the table view cell subclass from the data source (often the view controller). Let the cell do the display work.
When you add your subview after dequeueing uour cell, give a tag to your subview. This way, when you dequeue a cell, you can first check for the presence of a subview with your tag, and if it exists, remove it before adding your new view:
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
...
// try to dequeue a cell
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:<yourCellIdentifier>];
if( !cell )
{
// create a new cell if necessary
}
static int _myViewTag = 1000987 // give it a high int : low value are used by the system in cells
UIView *v = cell.contentView viewWithTag:_myViewTag];
if( v ) // subview with such tag already exists, so remove it.
[v removeFromSuperview];
// now add your new subview
[cell.contentView addSubview:<yourView>];
// adjust height of cell to your view.
...
}
Try to add a new method in your cell class to reset cell to its default style and call this method after dequeueCell.
The most efficient way to manage this is to subclass UITableViewCell and adding all your required Views as properties. So now when a cell comes up for "recycling", you know where to find the old views, like :
[cell.myTextLabel setText:#""];
aaaand you're done.
UPDATE creating a subclass makes sense if you have only a small number of "TYPES" of cells. create a subclass for each. How much complicated it gets depends on your specific scenario. But i've done it and found it to be the most effective method.
UPDATE 2 or you could make multiple cells in the storyboard, and dequeue the appropriate one based on the data source, save all the coding.
I have a UICollectionView I use like a tool selection container. You have many tools (the cells), when you select one, the former selected is deselected, and so on... You can only have one tool selected at a time.
The problem is that I can't manage to have the cells selected. When I tap the cell, the collectionView:didSelectItemAtIndexPath: is called. I then reload the selected cell to change it's appearance (I change the alpha of the image) by using the [collectionView reloadItemsAtIndexPaths:#[indexPath]].
Well that reloads the cell ok, except one damn thing: in the collectionView:cellForItemAtIndexPath: the cell never get the selected property set to YES! So I can never change the alphabecause I never know when I must draw a selected cell or not.
Worse: [collectionView indexPathsForSelectedItems] is always empty!!!
I don't even mention the collectionView:didDeselectItemAtIndexPath: that is never called...
Well, if someone can help me understand what is going on, thanks in advance...
When you call reloadItemsAtIndexPaths: the collection view discards those cells and creates new ones, therefor discarding the selected state of the cells.
I'd suggest a couple of different options:
1.) In collectionView:didSelectItemAtIndexPath: call cellForItemAtIndexPath: to get a reference to the selected cell and update it's appearance there.
2.) (My Favorite) Use a custom subclass of UICollectionViewCell if you're not already, and override the method setSelected:. There you'll be notified when the cell is selected and you can update the appearance from within the subclass.
With regards to selecting multiple cell at once, you should try the allowsMultipleSelection property [myCollectionView setAllowsMultipleSelection:YES] The docs for that are here: https://developer.apple.com/library/ios/documentation/uikit/reference/UICollectionView_class/Reference/Reference.html#//apple_ref/occ/instp/UICollectionView/allowsMultipleSelection
Otherwise, #daltonclaybrook's answer is sufficient.
I have a UITableView, to which I add cells via UIButton. On creation the cell gets its textLabel & detailTextLabel from 2 arrays. However, if an item with the same Title already exists in the table, I want to change the detailTextLabel.text of the existing cell without adding a new cell.
So is there a way to update the detailText of a certain UITableViewCell when it was already created with some value?
Maybe I should just remove the old one and add new?
Creating of a UITableView cell should be just that, creation and not population of data, since we re use cells we should always assume the cell data is stale and needs a refresh, therefore you should always have a way to reset the values of the cells, if you have a custom cell you should expose the controls you are using and set their values accordingly in cellForRowAtIndexPath, if you require to change a cell you should either change the data source values and reload the cell via - (void)reloadRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation , or grab a hold of the cell with cellForRowAtIndexPath and change the values accordigly... my point is no need to recreate the cell..