I've got a UICollectionView in a modal view controller in my app. When the modal view is brought up, one of the collection's cells is set as selected based on certain data I pass into the modal view from my home view.
I need to programmatically scroll the selected collection cell into view once the modal view with the collection appears... but using scrollToItem(at:at:animated:) while the collection view is being populated (in cellForItemAt) doesn't seem to work.
So while I could easily just use the indexPath available to me in cellForItemAt to scroll to the selected cell while populating the collection, since that isn't possible, I can't figure out how to scroll to the currently selected collection cell after the collection is fully populated and presented.
I can't even use a heavy-handed approach like looping through all collection cells and checking which is selected manually, since it doesn't appear possible to loop through cells that aren't currently visible.
Help?
Add a variable on Top.
private var didLayoutFlag: Bool = false
Just pass the index number (indexNO) in viewDidLayoutSubviews method. I am using horizontal scrolling.
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if self.colllecitonView != nil {
if !self.didLayoutFlag {
self.colllecitonView.scrollToItem(at:IndexPath(item: indexNO, section:0), at:.right, animated: false)
self.didLayoutFlag = true
}
}
}
Related
Hi in my Apple TV application i have one left collectionview right collectionview.Like splitview.When ever i focus cell on left data will refresh on right and when i select any cell in right collection view i am refreshing left and right collectionviews with new data (Like next level).And when on click on menu i will refresh both collectionviews with old data (Like coming to previous level). I want to highlight cell in left collectionview with red colour but i am reloading left collectionview while going forward or coming backward so always first cell is highlighting with Red colour. Can anyone suggest how to maintain previous selection in left collection-views because i am using only one collectionview for left menu and just reloading data.
The easiest way to retain focus in a UITableView or UICollectionView is to use UICollectionView.remembersLastFocusedIndexPath = true. This will automatically restore focus to the last focused item in a collection/table view and also automatically focus on the first item if there was no previously focused item or if the collection view data is reloaded.
If you need more control, the next level is to set UICollectionView.remembersLastFocusedIndexPath = false and use UICollectionViewDelegate.indexPathForPreferredFocusedView from your UIViewController instead. This method is only called whenever focus changes to a collection view programmatically though (but not if focus changes to a collection view as a result of TV remote interaction).
Now to ensure that indexPathForPreferredFocusedView is called when you switch between the left and right collection views using a TV remote, you will need to intercept shouldUpdateFocusInContext to override focus switches between the left and right collection view programmatically:
override func shouldUpdateFocusInContext( ... ) -> Bool {
if let nextView: UIView = context.nextFocusedView, let previousView: UIView = context.previouslyFocusedView{
if (nextView.isDescendant(of:leftCollectionView) && previousView.isDescendant(of:rightCollectionView)){
setFocusTo(leftCollectionView) // will invoke delegate indexPath method
return false // prevent system default focus change in favor of programmatic change
}
else if (nextView.isDescendant(of:rightCollectionView && previousView.isDescendant(of:leftCollectionView){
setFocusTo(rightCollectionView) // will invoke delegate indexPath method
return false
}
}
return true
}
internal var focusedView: UIView?
internal func setFocusTo(_ view:UIView){
focusedView = view
setNeedsFocusUpdate()
}
override var preferredFocusEnvironments -> [UIFocusEnvironment]{
return focusedView != nil ? [focusedView!] : super.preferredFocusEnvironments
}
func indexPathForPreferredFocusedView(in collectionView: UICollectionView) -> IndexPath? {
...
}
Alternatively, instead of using setFocusTo( collectionView ) + indexPathForPreferredFocusedView, you can just use setFocusTo( collectionViewCell ). Overriding indexPathForPreferredFocusedView is more robust though since it catches all cases where focus shifts for reasons other than user interaction (ex: system focus update due to an alert displaying + dismissing)
I have checked, tried many solutions on stackoverflow and from many website I searched.
My problem: I have a collection view inside table view cell. My data must be loaded 1 time in table view ( viewdidload).
When I pass data to collection view inside table cells, it's not appear because I need to reload collection view again.
So I do: Data -> inside cellforrow of table view -> Pass to collection view -> cell.collectionView.reloadData()
This cause a problem about scroll performance: collectionView.reloadData() call over and over again when I scroll ( this right because of resuable cells architecture of table view.
Here my code in cellforrow of tableView:
let cell = tableView.dequeueReusableCell(withIdentifier: SubCategoryCellID) as! SubCategoryCell
if isFetched {
cell.shimmeringView.isShimmering = false
cell.shimmeringImageView.isHidden = true
cell.shimmeringView.isHidden = true
cell.listLocation = nestedSubLocation[indexPath.item]
cell.collectionView.reloadData()
}else {
return cell
}
Solutions I tried:
+ Create static cells and get cells to display in cellForRow (it's totally fix scroll performance but I think it not good for memory management and it's not working if parent is collection view).
+ Reload data when scroll stop: it's still need to reloadData in loading first time and wrong data if I dont reload again.
To fix that, anyone have an clever approach to fix scroll performance ?
Put this code after cell.collectionView.reloadData()
cell.collectionView.scrollRectToVisible(CGRect.zero, animated: false)
I am trying to create a UITableView similar to the About section of the iOS settings. I have my initial table view, which I populate dynamically (already working), and which has disclosure indicators for each of its items. When I click on an item in this view, I tell the navigation controller to slide over to a static UITableView (pictured below). I instantiate the static table view from the storyboard using its ID, and before I transition to it, I'd like to fill it with dynamic values according to which item it's describing from the initial table view. Basically, how do I set the Right Detail portions of cells in a static table view in my code.?
The pseudocode I'm looking for goes something like this (exists inside the controller class for the initial table view):
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let customData: [String:String] = getDataForCell(atIndexPath: indexPath)
let descriptionView = storyboard?.instantiateViewControllerWithIdentifier("keyDetails") as! KeyDetailsController
descriptionView.getCell(forRow: 0, inSection: 0).rightDetail.text = customData["serverName"]! // changes "A Fake Server" to an actual server name
}
Just to summarize our discussion in chat: To update those labels, you just create IBOutlet reference to the labels.
The key issue here is that you're trying to update these outlets immediately after instantiating the view controller. But the outlets are not configured until the view is loaded, something that happens during the process of transitioning to the new scene. So you should:
Create String (or whatever) properties in the destination controller;
Populate these properties after the view controller is instantiated. Where yo do this depends upon how you're transitioning to the next scene:
If transitioning to the next scene programmatically (via showViewController, presentViewController or navigationController.pushViewController), then set these right after you call instantiateViewControllerWithIdentifier; or
If using a segue, set these String properties in prepareForSegue.
In viewDidLoad of the destination view controller, take these String properties and update the controls for which you have `IBOutlet references.
For more information, see Passing Data between View Controllers.
I have a subclass of UICollectionViewController that is nested inside a UINavigationController. The collection contains several cells (currently, 3) and each cell is as big as the full screen.
When the whole thing is shown, the collection view initally scrolls to a specific cell (which works flawlessly for each cell):
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if let path = currentlyPresentedPhotoCellIndexPath { // this is set in the beginning
collectionView?.scrollToItemAtIndexPath(path, atScrollPosition: UICollectionViewScrollPosition.CenteredHorizontally, animated: false)
}
}
However, the collection view refuses to scroll horizontally, hereafter, as if the user interaction was disabled. I am not sure what is happening, but this is what I have checked so far:
user interaction is enabled for the collection view
the next cell (right or left, depending on the scroll direction) is requested correctly which I found out by inspecting collectionView:cellForItemAtIndexPath:
the requested imagePath is the right one
scrollToItemAtIndexPath... does not work either if I try to trigger a scroll programmatically after everything has been loaded (nothing happens)
scrollRectToVisible... does neither
setting collectionView?.contentInset = UIEdgeInsetsZero before the programmatic scroll attempts take place does not change anything
the content size of the collection view is 3072x768 (= 3 screens, i.e. 3 cells)
Which bullet points are missing, here?
Although the post did not precisely tackle the root of my problem it forced me to ponder the code that I posted. If you look at it you will see that it basically says: Whenever the views need to be layouted, scroll to the cell at position currentlyPresentedPhotoCellIndexPath. However, and this you cannot see without any context, this variable is only set once, when the whole controller is being initialized. Thus, when you try to scroll, the layout changes, the controller then jumps back to the initial cell and it looks like nothing happens, at all.
To change this, you just have to enforce a single scroll, e.g. by doing this:
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if let path = currentlyPresentedPhotoCellIndexPath { // only once possible
collectionView?.scrollToItemAtIndexPath(path, atScrollPosition: UICollectionViewScrollPosition.CenteredHorizontally, animated: false)
currentlyPresentedPhotoCellIndexPath = nil // because of this line
// "initiallyPresentedPhotoCellIndexPath" would probably a better name
}
}
A big thanks to Mr.T!
I have a UITableViewController and when I click on it, it will show a DetailViewUIController.
I want to add a functionality which when I am in DetailViewUIController and I swipe to right, it will show the DetailViewUIController of next item and when left, it will show the previous item.
I find a link which kind of do that in swift. But it only has 3 static subviewcontroller.
https://medium.com/swift-programming/ios-swipe-view-with-swift-44fa83a2e078
The number of entries in my TableView can be pretty long, how can I do the same thing dynamically, i.e. without having static number of subviewcontroller created and add as 'addChildViewController'?
Update:
Thanks again #rdelmar for your help.
I am having trouble getting the ' set the contentOffset of the collection view to (collection view width) * selectedRow' to work.
In my prepareForSegue function, I have added:
x = Float(indexPath.row) * 375.0
var point = CGPointMake(CGFloat(x), 0)
println ("***x=")
println (x)
detailController.collectionView?.setContentOffset(point , animated: false)
where detailController is UICollectionViewController.
and in the
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as DetailViewCell
// Configure the cell
println("DetailViewController in cellForItemAtIndexPath()")
println(indexPath.row)
cell.myitem = allItems[indexPath.row]
return cell
}
And I always see cellForItemAtIndexPath trying to get 0th element of the allItems (that is the whole collections of all my objects.
So setContentOffset() does not change what I am displaying in the Detail View regardless which item I click in my TableView to launch the Detail View.
Any idea to solve this?
Thank you.
There are a lot of different ways you could do this. One way would be to make your detail view controller's view be a collection view (with paging enabled), whose cells are the same size as the screen. You would need to pass in the array that you use to populate your table so the collection view could populate its cells. This would be quite efficient, since the collection view would only ever need to instantiate two cells.