I'm looking for an in-depth breakdown/explanation of the iphone's view usage. Like, what controllers have what types of views, how they relate (child <> parent), how they can be nested, added and removed, etc.
Preferably something with some pictures would be nice too (I'm a visual learner).
But yeah, in-depth, technical, explanations of the iphone view system when used in IB/Obj-c would be awesome.
Also, feel free to give your breakdown or post to resources and I'll do the research.
Thanks
EDIT:
Ok, I'll be more specific. Is the View a stack - is it a queue? What does it look like when I call addtosubview?
What happens if the view isn't a full UIView, but say a smaller UI Control - will it be visible?
Say I have a UIView with a UITabView (2 items) and one content view is a UITtableView.
What's the parent view? What is the order of the children? Is that all dependent on how I add them to the view? In this case, the UITabBar control takes care of handling the views when I select the button.
When I call insertSubview how do I know what index to position it at?
This will be a good place to start (go from here to UIViewController and others that seem relevant). A UIView can contain many subviews of any type (they all inherit from UIView). To nest views, you add the subview to the superview [superview addSubview:subview]. You should also read up on Model-View-Controller.
Edit:
This SO question might also shed some light on the matter.
Edit edit:
Best I can do to answer your questions:
UIViews have an iVar subviews which is an array of subviews. Each of these also has such an array and can contain UIViews.
I assume you mean not full screen, generally, the topmost view is a UIWindow, and to this you add any UIView subclass you like, such as UISlider.
Your UIView has a subview UITabView, I don't know specifically, but I would guess it has two subviews, one of which is visible at a time, and one of these is the UITableView. Order is dependent on the order you add them in, and they will overlap each other depending on this order, but it can be changed with sendSubviewToBack and bringSubviewToFront.
If you want a specific view order, you're probably better off using insertSubview:aboveSubview: and the equivalent below, rather than at index.
Hope some of this helps.
Ok, I'll be more specific. Is the View a stack - is it a queue? What does it look like when I call addtosubview?
I like to think of it as a tree. The window is the root node, and it has any number of subviews. Those subviews can have any number of their own subviews, going down as far as necessary to create the full interface. The addSubview and removeFromSubview methods manipulate a view's "children".
What happens if the view isn't a full UIView, but say a smaller UI Control - will it be visible?
My understanding is that everything on the screen is a subclass of UIView, even the UIControl objects. Therefore, they behave mostly the same.
Say I have a UIView with a UITabView (2 items) and one content view is a UITtableView. What's the parent view? What is the order of the children? Is that all dependent on how I add them to the view? In this case, the UITabBar control takes care of handling the views when I select the button.
I'm not sure: David's answer has more info that should help.
When I call insertSubview how do I know what index to position it at?
I wouldn't worry about it: most of the time you just want addSubview and you won't care about the internal order.
Related
I've understood that I need to subclass a UIView t be able to draw inside it.
The thing I don't understand yet, is the philosophy of the way i must be done...
Let's say I have a view controller, and depending on context, I may want to draw a line into one of the subviews it manages, or a circle, or a rect, or a processed graphic. Or lets say two points that are moving inside a view into a defined rect and that display a bigger point when they are close.
How may I subclass and define the subview to make it able to do this only into its drawRect method ?
How does the controller, that manages more than this simple UIView (let's imagine you have a view controller that manages a view inside which there are many other view, and you want to make some drawings in two of them), and that knows what is needed to be drawn into the correct view (it's a controller, isn't it ?), may interact with the views ? And when the drawing is done, how may the views interact with the controller ?
I've read many doc about drawings (apple, web, forums, tutorials, ...), but I still can't touch the philosophy of the way this must be done.
it's very simple. Make a new class, OliverView, which is a UIView. (ie, it is a subclass of UIView.) In that view, make it draw stuff in a fancy way, inside drawRect.
Now make a UIViewController, called OliverVC. In storyboard put an OliverView inside OliverVC. (beginner explanation of how to do that).
In the OliverView, have properties "hours", "minutes", "seconds".
Now, in OliverView - in the drawRect - have a fancy way to display those values. (Pie chart, glowing letters, animation - whatever you want.)
Now, up in OliverVC, do some calculations to determine the time in Zimbabwe, for example.
Once you want a time displayed, simply set those properties in OliverView - - and you are done.
Your colleague could be programming the OliverView. You need know nothing about how she is going to display the time. Conversely, your colleague need know nothing about your calculations in OliverVC..
So, it's simpleL One part has the job of displaying the data. One part has the job of coming up with the data (doing whatever sort of calculation is relevant in the app).
It's the only architecture possible in a "real time" screen device where the views can and do change at any time.
In answer to your question below: you've forgotten that quite simply, if you have a button that would be a whole separate element. (Perhaps sitting "on top of" the OliverView.) So, it's easy!
The -drawRect method in your UIView subclass defines the onscreen appearance of the view. All drawing is done in -drawRect. Your UIViewController calls methods on its UIView to tell it to draw something differently or to perform some other action.
The UIViewController manages everything to do with the view that is not inherently associated with the drawing of the content. Data associated with the view is often stored in the controller.
I have a UIScrollView with textviews as subviews. Now in my app there are multiple UIScrollViews like these. And depending on the selection I display the appropriate UIScrollView on top of the previous view. This works fine in all cases except when the previous view has been a UIScrollView as well. In this case the behavior I get is of two UIScrollViews stacked on top of each other and both the views capture the scrolling events. The textViews from previous scrollView is also visible (not editable though) and overlaps and causes all sorts of issues. The thing is a full screen UIScrollView placed as subview to a previous view causes problems when the previous view is a full screen UIScrollView as well.
Any pointers on how to overcome this would be great. Is there anyway to notify the parent scrollview of the child's scroll events and move it the exact same way so this mess is masked?
Thanks!
UIScrollView documentation says:
Important: You should not embed UIWebView or UITableView objects in UIScrollView objects. If you do so, unexpected behavior can result because touch events for the two objects can be mixed up and wrongly handled.
As far as I know, it is generally not recommended to embed a UIScrollView subclass instance in a UIScrollView. In one of my projects, which is an IM application, I have a UIScrollView that contains many UITableViews, it works when you try enough but it really takes a lot of effort to handle subtle bugs and make it work properly.
It is really hard to say something useful for your problem without diving in to code, but i can recommend you to not add UIScrollViews one on to another like a stack. I'd try doing it by allowing only one UIScrollView at top, and removing others. When you need to show another one, remove the top one from view hierarchy and add the new one. I wish this helps, good luck.
Found a crude solution by presenting an empty view before I present the next scrollView. Added the scrollView as subview to this empty view (with a BG image) and added the to-be presented scrollView as a subview to it and then presenting this on top of the previous scrollView.
I've got several UI elements on my screen (programmatically) and am in need of an efficient way to give each subview a z-index setting, so I can stack certain elements over others.
Does anyone have a solution to this?
The plain -addSubview: method will add the new view on top of its siblings.
There are also a bunch of methods like bringSubviewToFront:, insertSubview:belowSubview:, etc. that you can use to manipulate the ordering, listed under "Managing the View Hierarchy" in the UIView Reference
I have an application with multiple views that contain subviews. I know that you can hide or make visible a view and its subviews by setting the hidden property to YES or NO. However with a number of views, to use the hidden property requires keeping track of what view is being displayed. I thought I could use sendSuBViewToBack: to hide a view and moveSubViewToFront to make it visible. However, these methods appear to only act on the specific subview and not its child subviews. For example, a view with a couple of labels on it, when sent to the back, the labels remain visible.
Is there any way to make this behavior work besides using the hidden property?
Thanks,
Jim
UIViewController seems like what you're looking for. Or rather, what you should be looking for.
I'm not quite sure what exactly you're having trouble with here. As long as you're keeping track of each "container" view (perhaps using a #property), you should be able to show/hide them on demand using a method in your code (which can be as simple as hiding all container views, and then showing the one you desire).
I have a problem, I can't solve properly.
In short: I want to create a single view (say: UIImageView) out of multiple subviews - i.e. it consists out of multiple ImageViews and TextViews. The thing is, I want to sort of 'render' them to be a single View.
Say, I take an image, add some description below, add a title above, and maybe another little image at the bottom. I want this whole thing to be a single UIImage to make it sort of 'listen' to one (e.g.) swiping gesture, which I cant tell to bring the new image to display.
Does anyone know the best way to achieve this? So far my results were fairly poor.
Any hints are welcome!
This is definitely possible. You seem to know about views and subviews, but should also read up on the "UIResponder" class and the "responder chain". The master view that you want to contain them all won't be a UIImageView, though, because that exists to just show an image. You can make all the ones you talk about subviews (addSubview: or in Interface Builder) of a plain UIView that you subclass yourself (say, MyContainerView), which then itself handles the gestures. If you want to take advantage of free scrolling on swipe, you could instead put your container view into a UIScrollView, which has its own set of semantics that you can leverage. For this latter, you should check out Apple's sample code for scroll views (don't have a link handy but should be easy to find) which embeds multiple image views in a scroll view.