I know that this question was asked a couple of times, but other solutions didn't work for me.
I have this model:
var notifications = [Notification]()
Notification:
let user: User (name, profileimage, etc)
let items: [Movies] (movie has image, name, etc)
So i display my notifications inside a tableview, each cell has profile info at the top and collectionview with items bellow.
Inside my tableviewcell, i have to reloadData of my collectionview to display correct movies. I know that probably reloadData method causes this lagging, but are there any solutions to avoid it?
TableViewcell:
var notification: Notification! {
didSet {
collectionView.reloadData();
}
}
I also tried this thing inside tablecell and call this method in willDisplayTableViewcell, but it doesn't help at all:
func setCollectionViewDataSourceDelegate(forRow row: Int) {
collectionView.delegate = self
collectionView.dataSource = self
collectionView.reloadData()
}
Images are loading using kingfisher, so it's fine in other places in my project.
userProfileImage.kf.setImage(
with: URL(string: profileImage),
options: [
.processor(DownsamplingImageProcessor(size: CGSize(width: 175, height: 175))),
.scaleFactor(UIScreen.main.scale),
.transition(.fade(0.2)),
]
)
I would comment out the code you have shown above as it will only get in the way and give false readings. My gut feeling is somehow you have managed to directly wire your notifications to your tableview / collection view and they are running on a background thread. What I would do to test this theory is wrap code anywhere where the UI is going to be updated with a perform on main thread like this
DispatchQueue.main.async { [unowned self] in
//Your UI update code within cellforRow / cellForItem (both table and collection view) Here
}
Try doing this one by one until you find the culprit and for a better solution try to refactor so you don't have to force this Main thread directive.
Related
I am using this tutorial to implement a pull-to-refresh behavior with the RefreshControl. I am using a Navigation Bar. When using normal titles everything works good. But, when using "Prefer big titles" it doesn't work correctly as you can see in the following videos. Anyone knows why? The only change between videos is the storyboard check on "Prefer Large Titles".
I'm having the same problem, and none of the other answers worked for me.
I realised that changing the table view top constraint from the safe area to the superview fixed that strange spinning bug.
Also, make sure the constant value for this constraint is 0 🤯.
At the end what worked for me was:
In order to fix the RefreshControl progress bar disappearing bug with large titles:
self.extendedLayoutIncludesOpaqueBars = true
In order to fix the list offset after refreshcontrol.endRefreshing():
let top = self.tableView.adjustedContentInset.top
let y = self.refreshControl!.frame.maxY + top
self.tableView.setContentOffset(CGPoint(x: 0, y: -y), animated:true)
If you were using tableView.tableHeaderView = refreshControl or tableView.addSubView(refreshControl) you should try using tableView.refreshControl = refreshControl
It seems there are a lot of different causes that could make this happen, for me I had a TableView embedded within a ViewController. I set the top layout guide of the tableview to the superview with 0. After all of that still nothing until I wrapped my RefreshControl end editing in a delayed block:
DispatchQueue.main.async {
if self.refreshControl.isRefreshing {
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0, execute: {
self.refreshControl.endRefreshing()
})
}
}
The only working solution for me is combining Bruno's suggestion with this line of code:
tableView.contentInsetAdjustmentBehavior = .always
I've faced the same problem. Call refreshControl endRefreshing before calling further API.
refreshControl.addTarget(controller, action: #selector(refreshData(_:)), for: .valueChanged)
#objc func refreshData(_ refreshControl: UIRefreshControl) {
refreshControl.endRefreshing()
self.model.loadAPICall {
self.tableView.reloadData()
}
}
The only solution that worked for me using XIBs was Bruno's one:
https://stackoverflow.com/a/54629641/2178888
However I did not want to use a XIB. I struggled a lot trying to make this work by code using AutoLayout.
I finally found a solution that works:
override func loadView() {
super.loadView()
let tableView = UITableView()
//configure tableView
self.view = tableView
}
I had this issue too, and i fixed it by embedded my scrollView (or tableView \ collectionView) inside stackView, and it's important that this stackView's top constraint will not be attached to the safeArea view (all the other constraints can). the top constraint should be connect to it's superview or to other view.
I was facing the same issue for very long, the only working solution for me was adding refresh control to the background view of tableview.
tableView.backgroundView = refreshControl
Short Answer
I fixed this by delaying calling to API until my collection view ends decelerating
Long Answer
I notice that the issue happens when refresh control ends refreshing while the collection view is still moving up to its original position. Therefore, I delay making API call until my collection view stops moving a.k.a ends decelerating. Here's a step by step:
Follow Bruno's suggestion
If you set your navigation bar's translucent value to false (navigationBar.isTranslucent = false), then you will have to set extendedLayoutIncludesOpaqueBars = true on your view controller. Otherwise, skip this.
Delay api call. Since I'm using RxSwift, here's how I do it.
collectionView.rx.didEndDecelerating
.map { [unowned self] _ in self.refreshControl.isRefreshing }
.filter { $0 == true }
.subscribe(onNext: { _ in
// make api call
})
.disposed(by: disposeBag)
After API completes, call to
refreshControl.endRefreshing()
Caveat
Do note that since we delay API call, it means that this whole pull-to-refresh process is not as quick as it could have been done without the delay.
Unfortunately, no advice helped. But I found a solution that helped me. Setting the transparency of the navigation bar helped.enter image description here
Problem can be solved if add tableview or scroll view as root view in UIViewController hierarchy (like in UITableViewController)
override func loadView() {
view = customView
}
where customView is UITableView or UICollectionView
I'm trying to implement data prefetching for my UICollectionView using the UICollectionViewDataSourcePrefetching protocol; however, the respective method is not being called.
The collection view has a custom layout. I have also tried with the regular flow layout, same results.
Upon data reload, I execute the following code to make the collection view have the size of its content to prevent scrolling within that collection view but in a scroll view outside the collection view:
func reloadData() {
viewDidLayoutSubviews()
collectionView.reloadData()
collectionView.layoutIfNeeded()
viewDidLayoutSubviews()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
collectionViewHeightConstraint.constant = collectionView.collectionViewLayout.collectionViewContentSize.height
collectionView.layoutIfNeeded()
view.layoutIfNeeded()
}
Maybe that has something to do with it?
What I have done:
my UIViewController does inherit from UICollectionViewDataSourcePrefetching
collectionView.prefetchDataSource = self (also tried using storyboard)
collectionView.isPrefetchingEnabled = true (also tried using storyboard)
I have implemented collectionView(_:prefetchItemsAt:)
Issue:
The prefetchItemsAt method is not being called. I determined that by placing a print statement in the method & setting up a breakpoint.
Like requested in the comments, I'll share my implementation for this issue here:
I created the tracker prefetchState which determines whether I'm prefetching at the moment, or not:
enum PrefetchState {
case fetching
case idle
}
var prefetchState: PrefetchState = .idle
Then, I hooked up the scroll view's delegate (the scroll view my collection view is in) to my view controller and implemented the scrollViewDidScroll method:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView == self.scrollView else { return }
let prefetchThreshold: CGFloat = 100 // prefetching will start 100pts above the bottom of the scroll view
if scrollView.contentOffset.y > scrollView.contentSize.height-screenBounds.height-prefetchThreshold {
if prefetchState == .idle {
prefetchItems()
}
}
}
In there, you can see that I check whether we're already prefetching. If not, I call prefetchItems(), as implemented here:
func prefetchItems() {
guard prefetchState == .idle else { return }
prefetchState = .fetching
someDownloadFuncWithCompletionBlock { (newItems) in
self.dataSource += newItems
self.collectionView.reloadData()
self.prefetchState = .idle
}
}
I execute the following code to make the collection view have the size of its content to prevent scrolling within that collection view but in a scroll view outside the collection view:
This sounds very broken.
Why are you doing this?
Prefetching on the collection view (from the docs) is triggered when the user scrolls the collection view. By making the collection view frame the same as the content size you are essentially disabling the scrolling of the collection view itself.
The collection view calls this method as the user scrolls
If you are forcing the collection view frame to be the same as the content size then you are entirely breaking UICollectionView.
The reason the prefetch isn't called is because every cell has been loaded already. Nothing is in prefetch any more. Because your collection view is displaying every cell at the same time.
If you want to scroll a collection view... let the collection view handle it. You shouldn't need to place the collection view inside another scroll view.
I've disabled delaysContentTouches in my tableview subclass using:
delaysContentTouches = false
subviews.forEach { ($0 as? UIScrollView)?.delaysContentTouches = false }
But in one of my sections, I still want to keep the delay. Is there a way to cancel the delay for certain sections or perhaps I can add a custom recognizer delay to a section?
Sections are not actual objects within a tableView, so my answer to your first question is no. The .delaysContentTouches applies to the entire tableView.
For your second inquiry, I believe that one way it could be possible is through setting a delay for desired cells' scrollView subview. In your tableView(cellForRowAt: indexPath) func, you could have something like this:
if indexPath.section == 3 { //or whatever your desired section is
for view in cell.subviews {
if view is UIScrollView {
let currentView = view as! UIScrollView
currentView.delaysContentTouches = true
}
}
}
This will find the UIScrollView in your cell's subviews in your desired section. It will then set the .delaysContentTouches property accordingly.
I have not personally executed this code, just researched it, so let me know if it works.
Edit
Apparently the UIScrollView in UITableViewCell has been deprecated, so the above method will not work anymore.
My next best suggestion to you is to use a UILongPressGuestureRecognizer. This will not be quite the same thing as delaying the touch, but could have a similar effect in real execution.
You could use it in the same tableView(cellForRowAt: indexPath) func as so:
let press = UILongPressGestureRecognizer(target: self, action: #selector(handlePress))
press.minimumPressDuration = 2.0 //however long you want
cell.addGestureRecognizer(press)
Whatever you are trying to achieve by selecting certain rows of your tableView could be placed in the handlePress func above which would be trigged upon the long press.
I am newbie in swift and I am building an app that similar to vine. First I open my app I am following the codes as you seen in the below
videoArray.removeAll()
let url = NSURL(string: "http://....")!
self.videoArray.removeAll()
Mellon.getExploreVideos(url,cache: cache, completionHandler: { (data, response, error) -> () in
dispatch_async(dispatch_get_main_queue()){
self.videoArray = data!
self.tableView.reloadData()
}
})
override func viewDidDisappear(animated: Bool) {
cache?.removeAllObjects()
videoArray.removeAll()
tableView.reloadData()
NSNotificationCenter.defaultCenter().removeObserver(self.tableView)
print("siliniyor")
}
In every 8 cell I am calling that getExplore func. I have about 80 videos in my tableview cell in my custom view cell I am building an AVURLAsset and AVplayer. I also set objects for cache in getExplore and when I close view controller I am removing all of them but as you seen from the picture all memory is not removing in every time I scroll tableview begin to end(I have 80 videos that tableView) and I change to view controller and back again I have 20 mb surplus in memory and at the end my app crush. What should I do for this problem? If the informations are not enough I can edit.
In your viewDidDisappear, make sure you call on to the super.viewDidDisappear as well. To quote the documentation-
You can override this method to perform additional tasks associated
with dismissing or hiding the view. If you override this method, you
must call super at some point in your implementation.
This might ease your memory issues. Give it a try.
I am developing an app, where I create buttons programmatically. When I click a button, it will request data from a database and show it in another view.
I use button.tag to determine what data to request, and I can only get the tag once the button is clicked.
However when I click the button, it shows nothing the first time. I must click it again to see the data which I want.
override func viewDidLoad() {
super.viewDidLoad()
//parseJSON(tagId)
createButton()
// Do any additional setup after loading the view, typically from a nib.
}
func createButton(){
var j:CGFloat=60
for var i:Int = 0 ; i < myImages.count;i = i+1 {
let myButton = UIButton()
myButton.setImage(UIImage(named: "carasusto.jpg"), forState: UIControlState.Normal)
myButton.setTitleColor(UIColor.blueColor(), forState: .Normal)
myButton.frame = CGRectMake(j, j+60, 50, 50)
myButton.tag = i //assign a tag to every button
myButton.addTarget(self, action: "segueToCreate:", forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(myButton)
j=j+60
print(myImages[i])
}
}
and
#IBAction func segueToCreate(sender: UIButton){
tagId = String(sender.tag)//tagId needs to fetch the information
parseJSON(tagId)
performSegueWithIdentifier("segueToView", sender:self)
}
func parseJSON(tagID:String){
Alamofire.request(.GET, "http://smarttags-001-site1.btempurl.com/SmartTagsRequests.aspx", parameters: ["AjaxFunc":"GetTagAttr","TagID":"\(tagID)"]).validate().responseJSON{ response in
switch response.result{
case .Success:
if let value = response.result.value {
let json = JSON(value)
print("JSON: \(json)")
self.TagName = json[0]["TagName"].stringValue
NSLog("\(self.TagName)")
self.ContentTitle = json[0]["ContentTitle"].stringValue
NSLog("\(self.ContentTitle)")
}
case .Failure(let error):
print(error)
}enter code here
}
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
var ViewTest : ViewTwo = segue.destinationViewController as! ViewTwo
var TagNameLabel = UILabel()
TagNameLabel.frame = CGRectMake(74, 112, 182, 64)
ViewTest.view.addSubview(TagNameLabel)
TagNameLabel.text = TagName
var ContentTitleLabel = UILabel()
ContentTitleLabel.frame = CGRectMake(74, 180, 182, 64)
ViewTest.view.addSubview(ContentTitleLabel)
ContentTitleLabel.text = ContentTitle
}
}
To follow up to MirekE's answer, here are some other steps you may want to consider:
Consider using Auto Layout in place of hard-coded frames, so your UI would adapt to different size classes.
Consider alternate approaches for showing an interactive list (of images) instead of programmatically adding buttons. For example, you could use a prototype (table view or collection view) cell. Cells are selectable and can take the place of a button. Other benefits include:
A scrollable container, should you have more buttons than would fit on screen.
A single segue (or selection) is handled by the storyboard prototype cell, instead of needing to make each programmatic "button" perform a segue (or action). Since you'd know which cell was selected, you'd no longer need a tag to figure that out.
Consider passing parameters to your destination view controller, instead of trying to instantiate and create controls in prepareForSegue. The destination's view is not loaded at that point.
Consider allowing the UI to feel more responsive, such as by performing the segue and showing placeholder details which you can then update once the network request completes. Otherwise, the user may have to wait for the network response before the segue occurs (which might make them think nothing happened and needlessly tap again, leading to an additional network request).
In general, Apple (or someone else) has already provided some way to do what you want, ideally leading to less code that you have to write, debug, test, and maintain to accomplish what you want your app to do.
Most likely cause of the problem is your call to parseJson followed by prepareForSegue. parseJson is asynchronous and you don't get data back from your service before prepareForSegue is called. As a first step, move the prepareForSegue to the completion block of the parseJson.