I am downloading images using NSOperationQueue.
I want to call a method reloadView of my view controller once the image download is complete.
However when the download is in progress, it is fairly possible that user has moved to a different view. This other view will also have a reloadView method (e.g. first view shows total downloaded images count, and second shows thumbnails of download images)
Basically what I want is that whenever an image download is completed, I should be able to call the reloadView method of the active view controller whichever it is?
How can this be possible?
I wouldn't take that approach. This is the kind of thing NSNotificationCenter is designed for. When your image has finished downloading, post a notification. In view controllers that need to know about it, listen for the notification in viewDidAppear: and stop listening in viewDidDisappear:. Your downloading code doesn't need to know the details of your view controllers or their status.
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I want to build some analytics into my app and I would like to send some data when user leaves current screen, though there are multiple ways he can do so (back button, other button, sidebar menu, etc). Is there any efficient way to do this? I really don't feel like implementing it to every possible button that can lead the user to different screen.
You should call your function inside viewWillDisappear, which is called every time the current view controller is about to disappear from screen. See the documentation of viewWillDisappear
Also see the view controller life cycle (thanks #Paolo for the tip) below (documentation).
I have an app that switch views using a segue when a button is clicked.
The second view loads data from the internet and it can take a couple of seconds.
I would like to know how can i display a loading view/splash screen in the meantime so the view could finish the loading and the app wont appear like it's doing nothing.
Thanks!
Check this library SwiftSpinner. It serves the purpose of your needs. It's really brilliant.
Call the necessary function from the library in the viewDidLoad method of your ViewController which loads the data from the internet. Remove this view in DidFinishLoading method of the NSURLProtocol (It's an optional func declared in that class which detects when the request to that URL is complete). The documentation is given in that library itself.
Sounds like you're looking for an activity indicator. I've used the custom class posted https://stackoverflow.com/a/32661590/3516923 with success. Just a note of warning, in his class he blocks all input while the indicator is in view. If you want to make it so your users can back out before things finish you need to remove UIApplication.sharedApplication().beginIgnoringInteractionEvents() and UIApplication.sharedApplication().endIgnoringInteractionEvents() from the start and stop animating functions.
If what you want is really a splash screen, have a UIImageView underneath the view that you're loading. Set the image to your splash screen image. Set the loading view to hidden=YES before it's shown, then set hidden to NO after it finishes loading. You could even set the opacity of the frontmost view to give you a fading effect.
1.You need to find a kind of indicator, suck like an activity indicator or something else to show the loading UI to the user.
2.Set the user interaction unable, so that the user won`t touchup inside repeatedly.
3.Start the indicator, set the user interaction unable when you load the server data, and stop the indicator animation when you finish, hide the indicator, enabled the user interaction.
Is any possible ways that I would like to know before html content was shown in uiwebview.
coz when I called to some url, It will take a few seconds to complete the whole page loading. Before loading was completed, some of the content was already shown. I would like to know before that content was shown or before start showing.
UIWebView has a delegate protocol called UIWebViewDelegate. Two methods you should implement are – webViewDidStartLoad: notify monitoring object of when a site will about to load and – webView:shouldStartLoadWithRequest: notify when there a certain request like click, submit, back/forward etc are being made
I have several view controllers each of them has a label or a button. I want to change visible view controller button's or label's text from the AppDelegate. I know that it is a bad practice but I in the AppDelegate runs a background thread which looks fow new images for user on the server and if there are ones it must update new images counter in the label on the navigation bar of the current dispalyed view.My idea was to use in the AppDelegate.m next code: (ControllerWhichLabelIWantToChange*) self.navigationControllerClass.visibleviewcontroller. ... But here I can't see a label or a button for which I define a property in ControllerWhichLabelIWantToChange. So the question how can I access elements of different view controllers from the AppDelegate and change them?
One suggestion, which might be better for you, is to use NSNotificationCenter to send notifications on various changes. Any view wishing to refresh themselves may respond to such notifications. This is a common practice. Say, for example, you are processing theme data in the background, and you've got 20 live views that require theming, you could post a notification when your background process has completed, and all views that are observing the notification will be notified, and they can update themselves.
I have always been a bit unclear on the type of tasks that should be assigned to viewDidLoad vs. viewWillAppear: in a UIViewController subclass.
e.g. I am doing an app where I have a UIViewController subclass hitting a server, getting data, feeding it to a view and then displaying that view. What are the pros and cons of doing this in viewDidLoad vs. viewWillAppear?
viewDidLoad is things you have to do once. viewWillAppear gets called every time the view appears. You should do things that you only have to do once in viewDidLoad - like setting your UILabel texts. However, you may want to modify a specific part of the view every time the user gets to view it, e.g. the iPod application scrolls the lyrics back to the top every time you go to the "Now Playing" view.
However, when you are loading things from a server, you also have to think about latency. If you pack all of your network communication into viewDidLoad or viewWillAppear, they will be executed before the user gets to see the view - possibly resulting a short freeze of your app. It may be good idea to first show the user an unpopulated view with an activity indicator of some sort. When you are done with your networking, which may take a second or two (or may even fail - who knows?), you can populate the view with your data. Good examples on how this could be done can be seen in various twitter clients. For example, when you view the author detail page in Twitterrific, the view only says "Loading..." until the network queries have completed.
It's important to note that using viewDidLoad for positioning is a bit risky and should be avoided since the bounds are not set. this may cause unexpected results (I had a variety of issues...)
This post describes quite well the different methods and what happens in each of them.
currently for one-time init and positioning I'm thinking of using viewDidAppear with a flag, if anyone has any other recommendation please let me know.
Initially used only ViewDidLoad with tableView. On testing with loss of Wifi, by setting device to airplane mode, realized that the table did not refresh with return of Wifi. In fact, there appears to be no way to refresh tableView on the device even by hitting the home button with background mode set to YES in -Info.plist.
My solution:
-(void) viewWillAppear: (BOOL) animated { [self.tableView reloadData];}
Depends, Do you need the data to be loaded each time you open the view? or only once?
Red : They don't require to change every time. Once they are loaded they stay as how they were.
Purple: They need to change over time or after you load each time. You don't want to see the same 3 suggested users to follow, it needs to be reloaded every time you come back to the screen. Their photos may get updated... you don't want to see a photo from 5 years ago...
viewDidLoad: Whatever processing you have that needs to be done once.
viewWilLAppear: Whatever processing that needs to change every time the page is loaded.
Labels, icons, button titles or most dataInputedByDeveloper usually don't change.
Names, photos, links, button status, lists (input Arrays for your tableViews or collectionView) or most dataInputedByUser usually do change.