I'm doing an app that uses a TabBarController and each Tab uses its own navigation controller.
The app has dynamic content and I use viewDidDisappear viewDidAppear methods to create or destroy the objects that I need each time I enter or exit into the ViewController.
My problem is when I start to sail very fast and I don't give time to load the Threads that I use for uploading content such as XML peta app or destroy objects when I leave the ViewController.
How I could control the tabs of the navigationbar or tabbarviewcontroller for not respond until the viewcontroller has loaded all contents?
Excuse me if I'm not well expressed. Thanks!
No matter you use synchronous request or asynchronous request, just show an UIAlertView while loading the data. This will both serve as a notification to the user that something is being loaded, and the it will block the interactions with all the other views on the screen.
As others have suggested in comments, I believe that what you want to do is rearrange the order in which things are triggered. Perhaps something like this:
On viewWillAppear:, clear (or disable or whatever is appropriate) your objects that are no longer valid and begin the load-new-content thread. Perhaps display a UIActivityIndicator or similar.
On viewWillDisappear:, tell the load-new-content thread that it can stop, its results are no longer needed. If you put up an activity indicator, take it down.
At the end of the load-new-content thread, take down any activity indicator, update the UI with the new contents and activate.
I don't really see any way around this -- if the UI is not valid until the new content is loaded, then you have to wait for it.
Another solution might be to cache the contents from the previous fetch, and always display those on viewDidLoad. Then, at the end of your new-content-thread, cache the new contents, and update the UI.
Related
Most of the iOS apps I use are very responsive, when I tap on an element it goes to the next view right away. In my app, some of my view controllers take 0.5-1.0 second to load.
My code is all in the viewDidLoad method and I'm pretty sure that's the problem but I can't move anything out since I need every single element that I instantiate.
A solution I thought is to move all the work I do in viewDidLoad in a thread then call the main thread when I'm ready to call addSubview, would that work even if UIKit is not thread safe? Or is there something else I'm missing?
Try to move some code you might have in viewDidLoad to viewdidAppear. viewDidAppear is being called once the view is presented. If you have to make some hard work, do it there and maybe show aa spinner somewhere while you do that.
What are you exactly doing in viewDidLoad? Btw remember that a view is only loaded when you need it, if you want to switch between views faster I can suggest you to create an initializion phase where you call -view on all the view controller you want to show, maybe helped with a spinner or a progress bar. but pay attention this would work only with intensive loading task and not memory consuming tasks. It sounds very strange your request, so is better the you try to explain better why your viewDidLoad is so slow, maybe there is something wrong.
Define your UI elements in Xcode as part of designing the interface. That way, Xcode can compile your storeyboard or xib files into the rapidly loading binary form.
I have a UITableView which loads its data from the web. It takes a while to load this data and therefore I would like an acitivity indicator to animate while the data is loading. I am doing the following in my attempt to make this work:
1) In viewDidLoad I add an observer to listen to when the data loading is done and after that I call loadDataFromWeb
2) loadDataFromWeb creates the activity indicator, adds it as a subview to self.view and then it loads the data. At last it posts a notification (the one that viewDidLoad observes) to indicate that the loading process is done.
3) Finally, when the observer catches the post from loadDataFromWeb, it calls removeLoadingScreen to remove the indicator.
Pretty obvious I am not seeing my indicator view. If I comment out the line that removes the indicator, it stays on the screen when everything is loaded. I am aware that I'm probably messing around with which methods are called when in the process, and this is where I need help.
I should mention that the whole purpose is that instead of the user's looking at a screen on which nothing is happening (while the data loads), I want a activity indicator to show up to indicate that there's something going on here.
Thanks
#Muncken have a look at this MBProgresHUD project, this will help you a lot to do a downloading progress in background (secondary thread not main thread) and shows a activity indicator over you view -
https://github.com/matej/MBProgressHUD
I've made a custom activity indicator (actually just an imageView)
When user clicks something and I expect it will take a bit long to process(alloc a UIViewController and push on to navigation stack),
I alloc the indicator and add it as subview of current view just before the lengthy process starts.
Strange thing is, indicator doesn't show up until the push (left-right) animation starts.
Is it because the lengthy job takes the system, and ui drawing for activity indicator is delayed?
Am I doing something wrong here?
Thank you
Edit
Looks like I can do the "push" in background.. i'm trying it now
IPhone SDK - Leaking Memory with performSelectorInBackground
Is your job synchrone or asynchrone ?
If it's the first case, then it can be the problem.
Check all the method like :
[ self performSelector:<#(SEL)aSelector#> ];
You can thread this to avoid your [potential] problem.
Good luck.
You should process your lengthy tasks in the background. The UI won't update if you block the main thread.
So you have to refactor your app, the alloc and push of the viewController should happen within the blink of an eye, because you can't do this in the background.
But you can do the processing (downloading data I guess) in the background.
There is plenty information available about background processing. The way to go varies heavily on what you want to do exactly.
I allow the user to manage records on other views. I set a flag if certain changes are made.
Then on the flag (where the data changes will have an impact) I run some methods / queries which create the data which is used in my table view(s). This workload currently happens in viewWillAppear(s).
This could take a few seconds and I'd like to show my progress indicator view which I wrote today, it uses a transparent view with a activity indicator in the center of the view.
[self performSelectorInBackground:#selector(startupStuff) withObject:sender];
However, viewWillAppear won't wait while I run the the work in the background.
Ideally I'm looking for a quick fix to work around this problem.
Any ideas ?
However, viewWillAppear won't wait while I run the the work in the background.
That's the whole point of it, isn't it? At the end of your startupStuff method, you should call another method on the main thread (with performSelectorOnMainThread:...) that is used to (a) inform the controller that your data is ready, (b) reload the table view and (c) dismiss your progress indicator view.
I have a UIViewController subclass that loads a bunch of images for each cell in a tableview asynchronously which is handled by a separate download class. I keep a list of all of these download requests in a dictionary which is keyed to the index of the cell that is requesting the image.
My question is i where should i put the code that cancels the image download if the viewcontroller is popped off the navcontroller? I need to do this because if the user hits back while there are still images being downloaded (which could take a while) then when they are finished downloading the viewcontroller has already been released.
I cant put it in the viewWillDisappear method because i do not want to stop the download if the user clicks on a separate tab and only when the hit the back button. For now i put this code in the viewcontrollers dealloc method which works fine although it doesnt seem right for some reason. I thought of using the viewDidUnload method but it seems this is only called when there is a low memory warning?
Any ideas?
dealloc is the perfect place for this as the view controller gets deallocated and you are responsible to clean your stuff up.
You may want to consider putting the code in viewWillDisappear: anyway, after all if the screen you are navigating to needs anything loaded it will be slowed by the background image load...