I'm creating an application in which there's the Main Page that holds a header, a footer, and a dynamic ConventView in the centre.
Depends on the button that was clicked (either in the footer or inside the page that is shown in the contentview) the view in the ContentView is updated/changed.
Thus, I needed to make the ContentView act as a bindable control.
To make it work, I maintain in the ViewModel of the MainPage, a stack of tuples .
Every time the content should be changed in the ContentView, I push the current BindingContext (some ViewModel instance) into that stack, paired with the page that is currently displayed in the ContentView. (or pop from the stack if I need to go back to the previous view)
After that, I set the ContentView to the requested View with its matching ViewModel as the BindingContext.
I noticed that the procedure of changing the BindingContext - is a performance issue. most of the time, changing the BindingContext can take 4-6 seconds(!!).
How can I solve this performance problem (without destroying the navigation mechanism I built)?
Thanks,
Related
I've been working with some UIScrollView objects that are longer than the view controllers they are contained by (this is in storyboard). Right now if I want to move objects that aren't initially shown I have to resize both the view controller and the scroll view. I also have to do this to add new objects to an initially non-displayed area. I know that I can do these things with the dimension inspector, but if I do that I can't tell what the layout looks like.
Is there another way to do this? I haven't been able to find a way to make the scroll view "scroll" inside of storyboard/IB. And it's kind of a pain to do layout this way.
Lets say I have a scene which includes a UIView container on the top half of the screen, and a UIView container on the bottom half of the screen and a few buttons at the very bottom of the screen.
Basically the bottom container will always display static text while the buttons across the bottom will change the content of the top container which may include an image, more buttons, or more text depending on what button is pressed on the bottom. Also each time a bottom button is pressed the top container is transitioned to the new view with a flip from bottom transition.
I have achieved this purely programmatically, but decided to convert my app to a storyboard file since it makes producing the rest of my app much faster and simpler, plus makes the code not look like a crazy mess.
My limited understanding of storyboards seems to deduce that I would need a separate story board scene for every UIView change, and Apple's coding conventions with storyboards seem to imply that we should use a new ViewController every time you create a new scene. All this adds up to an even bigger mess than I currently have.
Is there a better way of doing this? Am I misunderstanding something? If I am not confused, is there some way to make all these scene and view controller duplication cleaner?
The storyboard editor makes it difficult to do what you're describing, because it doesn't let you edit freestanding views associated with a scene.
I suggest you just create a separate nib (not storyboard) for each of the top-half views. These can exist separate from your storyboard. Your view controller (which is instantiated from the storyboard) can then load whichever nib it needs when a button is pressed, and put the view from the nib into its (the view controller's) top-level view.
There must be a way!
I accidentally opened one one day (see attached image). Although I have no idea how I did it and really really want to know, I cannot reproduce it, nor close it. The UIView opened when I was dragging my connection for the table header view from the Connections Inspector to the list of controls on the left side of the screen (not to the actual UIViewController).
I too am reworking a project with storyboards and have a similar problem with multiple views per UIViewController.
In this case it is a table header. I have other UIViewControllers in the project with the same configuration but I cannot get them to pop up either.
I have a series of UIViewControllers throughout my application. Most of them have the navigation bar but some of them hide it.
The problem is that sometimes as you transition between a view with or without navbars to another view with or without navbars there is a black box that replaces the navbar during the transition. This problem was discussed here: Hiding a UINavigationController's UIToolbar during viewWillDisappear:
This solution is fine and it does get rid of the black box, but I really don't want what was described as a "Cheshire Cat" disappearance. I've tried myriad solutions using prepareForSegue, ViewWillAppear, viewWillDisappear, etc. The best I can do is change the scenario in which the black bar shows up.
By this I mean, there are four combinations of view transitions between the two navigation bar states (hidden vs. not-hidden):
Hidden - Hidden
Hidden - Not Hidden
Not Hidden - Hidden
Not Hidden - Not Hidden
No matter what solution I've tried, at least one of those combinations results in my black box rearing its ugly head. The problem I have is that I've been unable to find anywhere that I can get a reference to the source view controller and the destination view controller when popping a view off of the navigation controller's view stack.
If I could get both references in the same event, I could simply determine what the combination is and handle the behavior appropriately like I would in prepare for segue.
Now, I know that "it's not possible" is a reasonable (and even a probable) answer, but I won't accept that as a solution alone. If it is indeed not possible, I'd like thoughts on a reasonable alternative. For example, I could handle all view controller popping manually (including the default back button) and thus could get the "upcoming controller" from the navigation controller's stack.
I would just prefer a solution using built in APIs or at least a solution where my controllers didn't have to be aware of their own navigation bar states.
Thanks a lot,
Patrick
I think UINavigationControllerDelegate is what you're after. It declares two methods:
-navigationController:willShowViewController:animated:
-navigationController:didShowViewController:animated:
All you need to do is set yourself as the delegate of the parent navigation controller and implement these methods to be notified of incoming view controllers.
Having said that, I've never needed to resort to this for hiding and showing navigation bars. Strictly speaking, view controllers where the navigation bar will always be visible never touch the navigation bar's visibility. When I'm moving into a view controller where it needs to hide, that view controller is responsible for hiding and setting it back to its prior state before disappearing. Following these standards has proven reliable for me.
My UINavigationController's navigation bar is kind of static. This means, there is no back button, because going back in the stack is done via the first entry of the UITableView the controller holds. The title also always shows the name of the root item.
To achieve this I have added my own custom view to UINavigationController.NavigationItem.titleView
It looks a bit odd if a new controller is pushed in: the old navigation item vanishes, just to get replaced by one looking exactly the same.
Is there a way to prevent this behavior? I want the animation for the content of the controller, so pushing the new controller without animation is not an option.
Add your own UINavigationBar and implement your own delegate and custom animations for the content views.
It sounds like you'll only need one UINavigationItem, so that makes this model easy to manage.
I have an application thad loads in plugins that have their own UI.
There is an IBOutlet called ContainerView in my AppDelegate.
When the plugin loads, it puts its own view (that is stored in a xib in the plugin bundle) into the Container view like so
[ContainerView addSubview:viewFromPlugin];
When the view loads, everything is fine but when I press tab the only controls that get any focus are ones outside of the ContainerView and none of them inside it get focus.
I've tried setting the container view as the initialFirstResponder and I've tried hooking up the nextKeyView from the last button in the tab order to the ContainerView.
Thanks.
I've tried setting the container view as the initialFirstResponder and I've tried hooking up the nextKeyView from the last button in the tab order to the ContainerView.
Is that what you want to do? Make the container view the key view? It doesn't sound like it; it sounds like you want the plug-in view (or a view within it) to become the key view.
This section of the Apple documentation explains all of the different aspects of the key view loop. I believe you'll want to either set the nextKeyView of the container view as well as the view before it, or override the container view's nextValidKeyView method—possibly both. You might also try setting the previous view's nextKeyView directly to the plug-in view's nextValidKeyView, skipping over the container view entirely.
Did you try calling the becomeFirstResponder method on your ContainerView?
http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIResponder_Class/Reference/Reference.html#//apple_ref/occ/instm/UIResponder/becomeFirstResponder
UIView classes inherit from UIResponder.