I have a simple question regarding the method removeFromSuperview()
When for example I use it to remove a UIView, do I remove also all of this view subviews?
I tried to search online but didn't find anything explanatory at least to me.
Yes. Basically, that is what a subview is. What you do to a superview, qua view, you do its subviews. Move it, hide it, show it, transform it, change its alpha, whatever.
Another way to think about it: what does it mean for a subview to have no superview in the interface? It means the subview is not in the interface. Well, you just took the superview out of the interface.
And we can go further. The superview owns the subview. If you remove the superview, by default, it is destroyed. In that case, the subview is destroyed too; it has no owner any more.
Related
I want to redraw a view.
When I touch a button, my view have to redraw itself. (have to call viewWillAppear)
But view's setNeedDisplay method doesn't redraw itself immediately.
Because I have to redraw it immediately, the method is not suitable to me.
I tried to remove all of viewController's view's subviews and to change viewController's
view to other view.
But these didn't work. (don't redraw)
I need your help acutely.
Thank you for your reading.
I think there are some misunderstandings here. Let's set things straight:
viewWillAppear: has nothing to do with the drawing of the view.
It's true that setNeedsDisplay doesn't redraw the view instantly, but we're talking milliseconds. So that's not even relevant.
Since you want viewWillAppear: to be called I'm assuming that what you call redrawing the view really should be referred to as relayouting the view. I assume that what you do in viewWillAppear: is setting the frames of you're views and possibly add/remove and/or show/hide some views.
I suggest that you move that code out of viewWillAppear: and into it's own method that will be called from viewWillAppear: and when you tap the button.
Since you don't provide your viewWillAppear: code this is all based on assumptions, so if my assumptions are wrong, please let me know and please do provide your "redraw" code.
Without more details it's hard to know exactly what you need but I might suggest you look at UIView::setNeedsDisplay. This will in turn cause your views drawRect: to be called where you can update the drawing.
[yourViewName setNeedsDisplay];
Let me start off by describing my situation. I have a main view that I wish to place a smaller scrollview subview in. Then later in code (in another method), I like to add some subviews (images and textviews) to that scrollview subview. And maybe even remove the image- and text-subviews later (in yet another method). So the image- and text-subviews ends up been a subview of a subview of the main view.
This is easily done, if it all happens inside the same method. But I can't seem to add a 3rd generation subview to the second subview from another method. Would expect something like:
[self.view.scrollviewSubview addSubview:anotherSubview];
How to target the scrollview-subview placed as subview in main view. Hope my question makes sense, it's really hard to describe in text.
I'm not sure to have understood ^^
But if your problem is to access a subview you don't have a pointer to, maybe you could set a tag to your subview
[ view setTag:9000 ];
Then later in your code you could search for this view with :
[ view viewWithTag:9000 ]
Don't forget that with viewWithTag you will get an UIView class. So if you need to get a specific class, you should cast it like
(MyViewSubclassed*)[ view viewWithTag:9000 ]
Good Luck !
is there a possibility to determine if an uiview obj is going to be displayed. imagine: you have 2 uiviews in an uiscrollview. now you are going to switch per gesture from the first view to the second. the first view now is NOT in the viewport. now you are going to go back to the first view. and now I want to be notified that this view is in viewport, or is redisplayed. the same has to be for the second view. I have not found any callback or something like this.
You make sure your UiViewController overrides viewWillAppear: (before it appears this method is called) or viewDidAppear: (after this method is called).
See: http://developer.apple.com/iphone/library/documentation/uikit/reference/UIViewController_Class/Reference/Reference.html#//apple_ref/occ/instm/UIViewController/viewWillAppear:
That depends what you mean by "switch". If one view is just scrolled out of the visible area of the scrollview, but still remains attached as a subview to it, then you may want to check if the bounds of your view overlap those of the scrollviews visible area.
You could do this by using UIScrollView Delegate's scrollViewDidScroll: method to implement a check for overlaps while the user is scrolling.
If however your view is actually removed from the viewstack, then you may want to subclass UIView and implement willMoveToSuperview: to check if the view has been added to the scrollview again.
I have a view which is similar to mail app. I have a scroll view and in that many other subviews. When the user clicks on any textview, it expands to show the text in it. e.g. "to" field in mail. I would want to resize the other subviews such that it starts below the expanded region. How can I do that.
I created the view through IB and I marked it for flexible top margin to facilitate this. But nothing happens automatically and hence I was wondering if I need to call sizethatFits/setneedsLayout.
When the subview resizes, call [[self superview] setNeedsLayout]. In your superview, implement -layoutSubviews to do the actual layout. You'll have to calculate everything yourself. Fixed/flexible margins are relevant to resizing the superview, not on peer views. The default -layoutSubviews does nothing at all; it just gets called at appropriate times.
If you need to force layout to happen at a particular point, then you can call -layoutIfNeeded on yourself or your superview. Read the docs on how this method works. Generally speaking you don't need to call this, though. It will usually get called at the appropriate time if you just use -setNeedsLayout.
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.