So my goal is to smoothly load the viewController with no split second bugs. I have a function that is used to determine what buttons to show when the view loads based off a field in a Firestore document. Here is the function:
func determinePurchasedStatusVerification() {
db.collection("student_users/\(user?.uid)/events_bought").whereField("event_name", isEqualTo: selectedEventName!).whereField("isEventPurchased", isEqualTo: true).getDocuments { (querySnapshot, error) in
if let error = error {
print("\(error)")
} else {
guard let querySnap = querySnapshot?.isEmpty else { return }
if querySnap == true {
self.purchaseTicketButton.isHidden = false
self.viewPurchaseButton.isHidden = true
self.cancelPurchaseButton.isHidden = true
} else {
self.purchaseTicketButton.isHidden = true
self.viewPurchaseButton.isHidden = false
self.cancelPurchaseButton.isHidden = false
}
}
}
}
I call this function in the viewWillAppear() of the vc but when I instantiate to that vc, this is the result...
The extra purchase ticket button shows up for a split second. Even though it's very quick, you can still see it and it's just not something a user would need to see. It's also the other way around when you click on a cell that's not purchased, the two bottom buttons show up for a split second. I just want to know how I can prevent this quick bug and be able to display a smooth segue with no delays in the button hiding. Thanks.
getDocuments is an asynchronous function, meaning it doesn't call its callback function immediately -- it calls it when it gets data back from the server. It may seem like a split second just because your internet connection is fast and the Firebase servers are definitely fast, but it's a non-zero time for sure. And, someone with a slower connection might experience much more of a delay.
Unless your callback is getting called twice with different results (which seems doubtful), the only solution here is to make sure that your initial state has all of the buttons hidden (and maybe a loading indicator) and then show the buttons that you want once you get the data back (as you are right now). My guess is, though, that you have an initial state where the buttons are visible, which causes the flicker.
Related
I've been trying to scroll UICollectionView with horizontal scroll, to the next page when isPagingEnabled property was set as true. I've been working on it for couple of days and I've made a lot of research, but I couldn't find any case like mine. If you already had this problem and if you already found a solution for it, it would be great sharing your solution way with me. Here is my current case;
func sampleTest() {
let collectionView = app.collectionViews[.sampleCollectionView]
collectionView.waitUntil(.exists)
let totalPageCount = collectionView.cells.count
guard totalPageCount > 0 else {
XCTFail("No pages could find in collection to take snapshot.")
return
}
for currentPage in 1...totalPageCount {
snapshot("Page\(currentPage)")
collectionView.swipeLeft()
}
}
Here, swipeLeft() method of XCUIElement is not working as expected in my case. When I call the method, it is not moving to the next page. It swipes a little bit and turn back due to isPagingEnabled = true statement.
In addition, there is another problem that collectionView.cells.count is calculated wrong. It always returns 1. I assume that the reason of the problem is about reusability. Because the other cells has not dequeued yet. Or collectionView.cells.count is not working as I guess?
I have this problem where (in several places) after executing an API call, the view does not refresh until a user action - like a btn click, tab bar switch, etc occurs. I have a feeling it is related to threading, but I can't seem to figure it out and I am new to iOS programming. I have tried different solutions with DispatchQueue etc, using it, and not using it. Trying to call setNeedsDisplay on the controller view. But no luck yet. The following is an example of code pulled right from one of my tab bar item view controllers:
func getEmployeeUpdates(){
self.showLoader()
APIAdaptor.shared.getEmployeeUpdates(forEmployee: Session.shared.employee, completion: {
(updates:[ScheduleUpdate]?, error:Error?) in
guard error == nil else{
DispatchQueue.main.async {
// self.resetMainScreen()
self.hideLoader();
}
return
}
DispatchQueue.main.async {
self.hideLoader();
self.ScheduleUpdates = updates!
self.tableView.reloadData();
}
})
}
func showLoader(){
NSLayoutConstraint.activate([
activityIndicator!.centerXAnchor.constraint(equalTo: self.tableView.centerXAnchor),
activityIndicator!.centerYAnchor.constraint(equalTo: self.tableView.centerYAnchor)])
activityIndicator?.startAnimating();
}
func hideLoader(){
print("Hiding");
activityIndicator?.stopAnimating()
}
I have attached two images. The first image is where the api call has finished (confirmed through testing) but the view is not refreshing. The loader is frozen. It should disappear after a call to hideLoader(). the second Image is after a click, or tab bar item switch.
I should also mention that in this example, as well as in other api calls the view will refresh eventually after completing, but only after a significant delay.
If anyone can help I would appreciate it very much!
This was a problem caused by the simulator on Xcode 10.1. If you run into this problem, try updating Xcode, or using a real device.
[EDIT]:
I think I have solved the lockup issue. While refactoring the didSelectRowAt prep for exit to be a blocking task in the ping async queue, I noticed that successful transitions would consist of one instantaneous move to rootVC followed by another animated transition to rootVC again. Made me realize I had two segues from my tableVC: one being the generic controller to controller segue (which is the intended segue method) and one from selecting the table cell.
I am unsure whether it was just the removal of the extra segue or the combination of multiple attempted solutions AND the removal of the segue that solved the problem. My guess is the latter as memory tells me that there was a time where there was only one segue and "fixes" weren't working then either.
tl;dr: Make sure you have no competing segues and that your async code is thread safe/has proper clean up.
[PROBLEM]:
I have a TableViewController which is a child VC of a rootVC under a Navigation Controller. In other words NavController[rootVC, tableVC].
The app starts in rootVC and is segued into tableVC through a UIButton. At tableVC's viewDidLoad, a network scan is done if no previous scan was completed before. Devices on the network are pinged at a certain port asynchronously as they are discovered. If these pings are successful, the IP Address associated with the device is used to populate a cell in the Table View. If this cell is selected, some app settings are changed through didSelectRowAt indexPath and an unwind segue is done to return to rootVC. viewWillDisappear is utilized as well to pass on values through isMovingFromParentViewController (previously done through prepare for segue but error was also present). The user is able to select the IP Address cell as soon as it appears in the table view, which is intended design.
That functionality all works. Most of the time. However, the app locks up SOMETIMES after a cell is selected WHEN a cell is selected while scanning is not done (this would mean that there can still be async pings happening/queued). I have a print at the beginning of didSelectAtRow which never happens when the lock up occurs. I also have an activity indicator view in the table view, which continues spinning when everything else is unresponsive. There is no crash or break from Xcode's side. It seems like that didSelectAtRow just does not happen and cannot proceed for some reason.
This is how my didSelectAtRow looks like
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
print("Cell was selected")
if possibleDevices.count != 0 {
selectedTableCellAddress = possibleDevices[indexPath.row]
let defaults = UserDefaults.standard
// Set the current cell's IP Address to the setting's IP Address
if selectedTableCellAddress != nil {
pingOperationsShouldStop = true
lanScanner.stop()
defaults.set(selectedTableCellAddress, forKey: "address")
}
}
}
Note that lanScanner is an instance of MMLanScan
My rookie knowledge gives me a guess that this is due to my async pings (the ping results are the last things that appear on the console). The async functions happen when a device is found on the LAN. It is encapsulated in a function like this:
DispatchQueue.global(qos: .userInteractive).async {
print("pingOperationsShouldStop? \(self.pingOperationsShouldStop)")
if self.pingOperationsShouldStop {
print("Skipping ping for \(addr)")
return
}
self.pingOperationsHaveStopped = false
let port = Int32(self.portStr)
let client = TCPClient(address: address, port: port!)
switch client.connect(timeout: 1) {
case .success:
print("connected")
DispatchQueue.main.sync {
self.possibleDevices.append(address)
self.numberOfPossibleDevicesCounted += 1
self.pingOperations.leave()
}
client.close()
case .failure(let error):
print("failed due to \(error) for \(addr)")
DispatchQueue.main.sync {
self.numberOfPossibleDevicesCounted += 1
client.close()
self.pingOperations.leave()
}
}
}
Note that possibleDevices has a didSet property observer that calls reloadData.
At first I thought that it only occurred through cell selection (i.e. NavCon's Back worked fine). So I programmatically called the popping of the view, to not avail. I tried reproducing the lock up through NavCon's Back button and have been able to do it once.
I'm not sure what code is relevant to share, so let me know if you need more information.
Thanks!
I have a UIView with two buttons on it. In the MyView class I have this code:
-(BOOL) canBecomeFocused {
return YES;
}
-(NSArray<id<UIFocusEnvironment>> *)preferredFocusEnvironments {
return #[_editButton, _addButton];
}
-(IBAction) editTapped:(id) sender {
BOOL editing = !tableViewController.editing;
[_editButton setTitle:editing ? #"Done" : #"Edit" forState:UIControlStateNormal];
_addButton.hidden = !editing;
[tableViewController setEditing:editing animated:YES];
}
The basic idea is that the user can move the focus to the edit button, which can then make the Add button appear.
The problem started because every time I tapped the edit button, focus would shift to the table view. I would actually like it to move to the Add button. I also want it so that when editing it deactivated, the edit button keeps the focus. but again it's shifting down to the table view.
So I tried the above code. This works in that focus can move to the view and on to the button. But once it's there, I cannot get it to move anywhere else.
Everything I've read says just override preferredFocusEnvironments but so far I've not been able to get this to work. Focus keeps going to a button then refusing to move anywhere else.
Any ideas?
If anybody is facing this issue, Just check if you are getting the following debug message printed in the console.
WARNING: Calling updateFocusIfNeeded while a focus update is in progress. This call will be ignored.
I had the following code :
// MARK: - Focus Environment
var viewToBeFocused: UIView?
func updateFocus() {
setNeedsFocusUpdate()
updateFocusIfNeeded()
}
override var preferredFocusEnvironments: [UIFocusEnvironment] {
if let viewToBeFocused = self.viewToBeFocused {
self.viewToBeFocused = nil
return [viewToBeFocused]
}
return super.preferredFocusEnvironments
}
I was calling the updateFocus() method multiple times while viewToBeFocused was either nil or some other view. Debugging the focus issues mainly between transition is really difficult. You should have patience.
Important to note: This depends on your use case, but if you want to
update the focus right after a viewcontroller transition (backward
navigation), You might have to set the following in viewDidLoad:
restoresFocusAfterTransition = false // default is true
If this is true, the view controller will have the tendancy to focus the last focused view even if we force the focus update by calling updateFocusIfNeeded(). In this case , since a focus update is already in process, you will get the warning as mentioned before at the top of this answer.
Debug focus issue
Use the following link to debug the focus issues: https://developer.apple.com/documentation/uikit/focus_interactions/debugging_focus_issues_in_your_app
Enable the focus debugger first under Edit scheme > Arguments passed on launch:
-UIFocusLoggingEnabled YES
This will log all the attempts made by the focus engine to update the focus. This is really helpful.
You can override the preferredFocusEnviromnets with the following logic:
-(NSArray<id<UIFocusEnvironment>> *)preferredFocusEnvironments {
if (condition) {
return #[_editButton];
}
else {
return #[_addButton];
}
}
After setting it, you can call
[_myView setNeedsFocusUpdate];
[_myView updateFocusIfNeeded];
The condition could be BOOL condition = tableViewController.editing; or sg like that.
If that now works, you can call it with a delay (0.1 sec or so).
I am trying to update my UILabel to a String from my Parse database.
My problem is the label will not update my firstnameLabel when I first sign in. But it WILL update, when i sign in (nothing happens), push the stop button in Xcode and then launch it again (still logged in) and then it updates the label.
How can I do this faster??
Here is my code:
var currentUser = PFUser.currentUser()
if currentUser != nil {
var query = PFQuery(className:"_User")
query.getObjectInBackgroundWithId(currentUser.objectId) {
(bruger: PFObject!, error: NSError!) -> Void in
if error == nil && bruger != nil {
var firstName: String = bruger["firstname"] as String
self.usernameLabel.text = firstName
} else {
println("Error")
}
}
} else {
self.performSegueWithIdentifier("goto_login", sender: self)
}
Hope you can help me!
Rather than trying to load the user object again by the id, try just doing a fetch instead.
[currentUser fetchIfNeededInBackgroundWithBlock: ... ];
By trying to load the object, you might be getting a cached version.
I read somewhere that it could be because of the fact that the could was put inside the ViewDidLoad. I tried to put it outside of that and it worked!
It sounds like you put it in the ViewDidLoad method. You should put it in the ViewWillAppear method instead. Here's an example.
1) ViewDidLoad - Whenever I'm adding controls to a view that should appear together with the view, right away, I put it in the ViewDidLoad method. Basically this method is called whenever the view was loaded into memory. So for example, if my view is a form with 3 labels, I would add the labels here; the view will never exist without those forms.
2) ViewWillAppear: I use ViewWillAppear usually just to update the data on the form. So, for the example above, I would use this to actually load the data from my domain into the form. Creation of UIViews is fairly expensive, and you should avoid as much as possible doing that on the ViewWillAppear method, becuase when this gets called, it means that the iPhone is already ready to show the UIView to the user, and anything heavy you do here will impact performance in a very visible manner (like animations being delayed, etc).
3) ViewDidAppear: Finally, I use the ViewDidAppear to start off new threads to things that would take a long time to execute, like for example doing a webservice call to get extra data for the form above.The good thing is that because the view already exists and is being displayed to the user, you can show a nice "Waiting" message to the user while you get the data.