I have a view controller that has a webview whose content is injected. I want to be able to preload/prerender the content before displaying the webview.
My solution was to create two webviews instead and swap which one is displayed. How do i do that?
I tried swapping the reference to the second webview, remove the first from superview and add the second to the superview. But nothing is showing up
If you want to pre-load your webviews, they need to be instantiated. If the webview isn't added to a parent view it may not load correctly. I would try keeping both webviews in the layout and just setting them hidden where appropriate. Setting them hidden will hide them from the user, but they will still behave as expected.
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What I'm trying to achieve is basically a Instagram profile type screen.
I'm trying to recreate the segmented control section and what's beneath.
I thought about putting a container view containing the segmented control and a scroll view that switches between 3-4 views.
I saw many ways of implementing this, with or without a scroll view (the one I'm not really a fan of is the .ishidden method).
My main concern is memory. I don't know if it's better to keep them in memory or load them from scratch and also how to do that. Can you point me in the right direction ?
The instagram app doesn't do exactly what you described-- it looks like the only the first two options within the segmented control swap out the view underneath. The last two navigate you to another view
You definitely want to load your views, assign them to strong properties, and then swap them out.
Add a Custom View in Interface Builder, that will be your container, and then connect it to an IBOutlet in your controller. You can instantiate your scroll views when the controller is instantiated, and then you can then add the scroll view as a subview to the container. Then when the segmented control is pressed, you can remove that subview, and replace it with the new subview selected.
Instagram would arguably have some of the largest views, as far as memory allocation is concerned, to swap out (several images). Yet you can tell that the scroll views are stored in memory because you can switch between them without reloading the images
I have a Navigation View Controller and many of it's child VCs have maps. And if I go down navigating through n views, I'll have always n-1 maps allocated in memory.
My idea is to deallocate a map every time the view controller disappears, and reallocate it when it appears again.
However, they were laid out using a storyboard, and their frames change depending on the devices orientation because I'm using constraints. This way, when the VC is loaded for the first time, it appears as on the storyboard. But when I deallocate it and I have to reallocate, I don't know how to set the frame correctly, or how to add the constraints properly.
What is the best way to do this?
You'll need to read up on creating constraints programmatically. You can use the debugger to log the constraints on your map view before deallocating it, and then write code to recreate those constraints when you add the map back in.
You have to read the property like user location and other attribute and save it before setting to nil and when you comes back check this object in viewWillAppear like
if(!mapView) {
allocate here and set the saved values
}
In my view I am using a UITableView that is controlled by a UITableViewController on the top half of the screen. The remaining screen is used for a UIScrollView that contains a view that is controlled by the main UIViewController.
When I perform a pull down to refresh in the UITableViewController, (for some reason if the number of table entries is less than or greater than the initial load value, the UIScrollView in the main UIViewController's frame gets changed to the screensize...
Essentially it breaks my paging unless I reset the scrollview back to the intialized size...
I have no idea why this happens as the UIScrollView is not used in the UITableViewController. The only scrollview that is used in the UITableViewController is the UITableView's to handle pull down to refresh...
Does anyone know why the main UIScrollView's contentSize gets changed randomly when it shouldn't even been accessible from the UITableViewController class?
Thanks
Just tried it here, and I can't duplicate your experience. I'm guessing you have an unexpected or inconsistent view/controller hierarchy? Look at the controller of the table and scroll views' common superview. Anything fishy there? Remember: view controllers manage sets of views. Container view controllers manage other view controllers and have special rules (see: The View Controller Programming Guide, esp. -addChildViewController:, etc.).
I'd suggest opening a blank project and trying to recreate the problem in its simplest possible form. If it's magically fixed, what's different? If it's still giving you trouble, send us a link so we can see the details of how you have things wired.
I am wondering what happens if a single instance of a UIView object gets added as a subview of multiple other views simultaneously.
If UIView:removeFromSubview: gets called then does it get removed from all superviews or just the currently displayed one?
For background:
I have a status-bar like view object that needs to be displayed within several different other views (each other view is managed by its own view controller).
[i.e. a) the user is in one view, b) something happens to make the status-bar-like view appear, c) the user switches to another view d)the status bar is still visible in the new view e) the status bar expires after a time and disappears from site. And so on]
Initially I implemented this by adding/removing it as required as a subview of the window, and this was managed by a singleton.
However due to some complications with some animations I have instead added it as a subview of each of the main view's for each of the view controllers.
Note that there are not multiple copies
When the view needs to be removed I am calling its removeFromSuperview:, and everything is all working perfectly.
However I am wondering what the situation is regarding the removal of the view, is it being fully removed or is there something else I need to do?
For example the view might get added to N view controller's views by calling addSubview as required (it will only get added to each view controller if that view controller actually launches)
However when it is being removed I am only calling removeFromSuperview: for the view of currently loaded view controller, not all view controllers it might have been added to.
Next time I navigate to one of these other view controllers it displays fine without the view being there, even though I didn't explicitly call removeFromSuperView.
As I said everything is working as it is, however at the back of my mind I feel there might be something missing?
Hope this was understandable.
You can only have it added to one view. Documentation is your friend!
(void)addSubview:(UIView *)view:
Views can have only one superview. If view already has a superview and that view is not the receiver, this method removes the previous superview before making the receiver its new superview.
From my point of view, having to add a same view to different parent views (and more important, from different view controllers) is an indication that something is wrong on the design...
However, if you really (really) need so, I had always thought that a view instance could have one and only one parent view... Moreover, you can access it by [myView superview] message, which gives you a UIView instance instead of an array... It may auto remove from its old parent before adding to a new superview?
About the design, what about creating it each time you need a new one and have a singleton to manage their status/logic?
Good luck with that!
I want to have multiple views in my application that I switch between.
What is the proper way to switch between UIViews that also supports UISplitViewController?
Is there a support way to switch or are Apple's controller classes designed to be root and root only?
I've tried having one root view and root controller and swap subviews in and out. One of the subviews is a UISplitViewController. It did not like the arrangement and does not display correctly. The detail view was not displayed, the master view displayed wrong orientation and wrong size.
I've then tried managing adding and removing one subview from the UIWindow in the app delegate. This works most of the time. However, the views added after the applicationDidFinishLaunching method do not appear setup correctly. They mostly look correct, however sometimes the orientation thinks its portrait when in reality its landscape. Also, when I try to display a popover, it shows up in an incorrect location. If I change the orientation, it redraws correctly. I've also have some random instances where the UISplitViewController view does not fully display, as if its frame is incorrectly sized.
Any suggestions heartily appreciated.
In applicationDidFinishLaunching, your objects haven't completed loaded from NIBs yet. Try using a viewDidLoad method instead.
What is the user-interface for switching between views? If one of these views represents a transient mode that the user enters and then exits, consider using a modal view. (See presentModalViewController:animated:.)
I would need more details about what you're doing to answer more particularly.