I' ran into an absolutely weird kind of problem I don't have a clue yet how to fix it, having been working on this without a break (except for eating, sleeping, drinking coffee and smoking) for almost two days now.
What I have:
I've got an UIScrollView inside my view controller, containing a certain number of textfields and a UICollectionView. With a button, I open another view controller for adding new data to the collection view. Back to my first view controller after the new data items have been added, I call invalidateIntrinsicContentsize on my UIScrollView and on my UICollectionView to resize them both to fit their content (I use Autolayout and let both of them hug their content). On both views I've implemented these methods to nicely fit their content, and this part works perfectly fine.
What my problem is:
If I add data to the UICollectionView in the way just described, and if I'm in landscape mode, the problems start: After getting back to my initial view controller and updating the intrinsic content sizes, the content of my UICollectionView is displaced - displaced in such a way, that the scrolling position of the content inside the UIScrollView before switching to the data-adding view now becomes something like a fixed content offset. If I scroll up now, I can reach at maximum that position of the content where it has been - by getting scrolled to - before I switched to the data-adding view controller.
Pictures (everyone loves that):
To illustrate that situation somehow difficult to explain, I appended two pictures. Red is the entire content area of the scroll view, dark green is the content, where both overlap the color is olive. The visible part of the UIScrollView is shown in the highlighted, bordered area.
Before updating the data, content is where it should be:
(source: grubbrother.com)
After updating the data and updating UI, content is displaced by former scroll position / contentOffset:
(source: grubbrother.com)
Please help me with this weird stuff. Unfortunately, I've got a tight deadline and need to move on with the project. Nevertheless I really don't know how to solve this or even what might cause it - I have absolutely no clue.
Despite I couldn't find out yet what causes the problem described in my question, I found a hack around it that at least somehow fixes the symptoms:
As I describe above, the unwanted content displacement that occurs when switching back to the UIViewController containg the buggy UIScrollView is equal to the contentOffset of the UIscrollView before switching to another scene.
Knowing this, I set the contentOffset to zero after my UIViewController disappears.
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
[self.scrollView setContentOffset: CGPointZero];
}
When the view reappears, I scroll down to the newly added content at the bottom of the UIScrollView in question:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
if (self.appearedFromActorsAdding)
{
[self.scrollView setContentOffset:CGPointMake(0, self.scrollView.contentSize.height - self.scrollView.frame.size.height) animated:YES];
}
}
Hope this helps anyone running into the same problem.
Related
I got a problem with Cocoa and its View redraw hierarchy.
I'm currently testing displaying (audio) levels in a meter style control and I'm using the MeteringView class from MatrixMixerTest example project from apple. This class is drawing the meter and only drawing the difference what got changed which looks like a very efficient class.
My project is splitted into 2 splitviews, in some are NSCollectionViews (Scrollview, Clipview) and in others are only static views. If I add the meter to those "static" views they work fine when these views call setNeedsDisplay:YES. If a meter is added to the view of a CollectionView Item it gets rendered, but loosing its drawn "old level" parts and its corners/background. I think this happens because the CollectionView item gets also called to be redrawn (which has a background image) and everything is gone. It is drawing some parts whats currently changing (the drawing works).
Is there a way to prevent the Item itself to be redrawn? Or, I dont know why it is not happening in those static views, because those views also have background images but do not draw over the meter.
Are there some tricks or whats different in a CollectionView than in a "normal" view?
EDIT: After reading about isOpaque (MeteringView isOpaque = YES) means it should not call the parent views drawRect if set to yes. Well that works for the static views, those MeteringViews do not call parents drawRect, but those in a CollectionView do however. I dont know why.
EDIT 2: I gave this topic another title, because isOpaque=YES in MeteringView is not stopping calling the parents drawRect in a CollectionView, in a normal view it is working. Are there some things to know about? I have to stop redrawing the CollectionView Item because thats the problem.
Thanks in advance guys
Benjamin
isOpaque is just hint to the system. It does not prevent other views from drawing their contents, it only means that it can sometimes skip making other views update their contents.
If your view is opaque, it should draw itself as opaque and completely fill its bounds.
I'm placing a few buttons in a simple rectangular NSview which acts as a custom toolbar. On first render the buttons/views come out as expected, but every time a button is pressed (and sometimes with no mouse interaction at all) artefacts start appearing.
Before
After
I can eliminate the artefacts by calling a [self.toolbarView setNeedsDisplay:YES] in all the action and focus methods but this seems like a hack, is there any clean way to deal with this?
It was a beginner's problem. In the drawRect method
- (void)drawRect:(NSRect)dirtyRect
I was using the param dirtyRect for drawing an outline of my view, assuming it was the view's bounds, where in fact it was only the area around the buttons that became dirty when they were pressed. The 'artefacts' were actually my outline being drawn in the wrong place.
By correctly using the bounds of the view
NSRect drawingRect = [self bounds];
the 'artefacts' no longer appeared.
You just try to set focus ring for a buttons to 'none' in IB.
I would like to programmatically allow the user to zoom away from a current page inside of UIScrollView and present them with an overview of multiple pages. Then allow them to touch/choose one of the pages to zoom in.
I have multiple sub ViewControllers for each page. The important aspect is that each ViewController contains detailed information, so I want most of that information to be visible when they get a "birds eye view" of what's happening.
What's the best way to do this?
Additional detail: pretend each UIViewController has a UiTableView within them. There's 5,6,3,1,0,10 Cells in each of these (respectively) is there a way to show all Cells at once in the larger view?
Perhaps is there a way to screenshot the Views and present them as smaller objects?
Currently I have the UIPinchGestureRecognizer already working, just need a way to control the transition of these viewcontroller into the middle. Is there a way to screenshot each controller and transition to a different view for selection?
If You want it for a pdf viewer, then maybe you can implement something similar to this:
https://github.com/vfr/Reader
When corresponding button is pressed - modally rises up a gridview with smaller pages. When taped on any - it then opens that page.
If it's not about pdf viewer, and You still desire the pinch-zoom effect, then maybe you can implement two different views - where - on one will be in grid - all viewcontroller thumbnails, and on other - scrollview. When you pinch -zoom out - scrollview alpha changes to 0, while gridview list alpha changes to 1. When taped on any viewcontroller thumbnail - alpha changes.
If You still want without fade-in fade-out, then it's even harder. On each pinch zoom movement, you need to recalculate each viewcontroller positions and sizes. and start moving them where they should be.
Hope that helps.. somehow..
I am trying to create a resize toggle animation on this simple custom TUIScrollView class (from TwUI open source project and very similar to UIScrollView) that I have built. It is called TUILayout and supports horizontal layout as well as vertical, animated insertions and removals and has a more declarative way of supplying data to it's cells that I prefer over delegation. It recycles views similar to TUITableView or UITableView. Anyway if you want to follow along, it's just one class and is here.
https://github.com/mrjjwright/TUILayout.
In the example code, the user clicks the blue button in the lower left and all the rows shrink smoothly to a size where the user can reorder and delete some rows (right click on a row in the example to see this in action), etc... and then the user toggle the rows back out to their original size by clicking the blue button again.
While doing this resize in setObjectHeight:animated I first resize my model objects that represent the rows, recalculate and set the contentSize on the TUIScrollView, cycle in all the new views (say 10 more views will fit in the shrunk view so dequeueReusableView and addSubview gets called 10 times) and finally I animate the frames of all the views to their size and location in layoutSubviews.
The result is that the scrollview correctly shrinks to a size where the scrollbar no longer displays, the views that are on screen animate smoothly down to their reduced size, but the newly added subviews that can now fit in the visibleRect animate in much later as one block of subviews.
So all the newly added subviews lag behind the views that were on the screen and I can't figure out why the animation isn't all happening together. I have tried lots of different combos of things with no luck including CATransactions. I am wondering if it has to with how a CAScrollLayer works or if somebody can help me think through this.
The more general issue is how to smoothly handle resizing animations on scrollviews that recycles their views and I have looked at several other grids out there in the iOS world and have got some inspiration but am looking for more.
Thanks!
I think I might have solved my own issue here (as I was making my bed this morning it hit me). I forced the current runloop to run after cycling in all the necessary subviews and very importantly not setting the contentSize of the scrollview until after the run loop completes and adds the needed subviews for the animation. In order to get the run loop to fire I used the trick from this SO question:
skipLayout = YES;
[[NSRunLoop currentRunLoop] runMode: NSDefaultRunLoopMode beforeDate: [NSDate date]];
skipLayout = NO;
If skipLayout is set TUILayout just returns from layoutSubviews so that the views just added are not immediately removed by the recycling layout code. Forcing the run loop to run made sure that all subviews were on the screen for the animation. After this I performed the resize animated layout. I updated the code on github if anybody is interested. I will leave this question open for a while to gain some further insight.
I subclassed UITableViewController and called it FeaturedGamesViewController. Ok, I also have a navigation controller to which I added this FeaturedGamesViewController as the root. All pretty standard stuff that you do in the App Delegate.
Also note that there is no NIB file created for FeaturedGamesViewController. Just subclassing UITableViewController and calling initWithStyle sets the style of the table and sets the dataSource and delegate and size automatically. Data Source and Delegate are obviously set to FeaturedGamesViewController.
- (id)init
{
// Call the superclass's designated initializer
[super initWithStyle:UITableViewStyleGrouped];
}
OK, You see that I have set the table size to "Grouped". In Landscape view on my iPad it has about 20 pixels of space to the top, left and right (Sorry can't post screen shot because I am new here and the system won't let me until I have accumulated a certain number of points)
I DO NOT want that! This is Landscape so I expect it to fill up the all the space between the navigation bar and the tab bar below. What is worse is that I have faked a grid with a Custom UITableViewCell but the space to the left and right make it so that if you click on that space, the entire row is selected thus betraying the sense that this is a grid.
Now I figure I should resize the table view in viewDidLoad or something but I don't know how. I cannot do initWithFrame because of potential memory leaks (and possibly resetting dataSource and delegate and autoresizeMask properties that were already set) so there must be a setter or something to reset the origin of the tableview to just beneath the Navigation bar and filling up the entire screen with size 1024X748. How do you do dynamically reset the size of the table view?
Then I got really frustrated and I decided to do it via a Nib file, that way I can set the the orientation to landscape and set simulated Navigation and Tab bars and fill the rest of the space with the table view. This worked! If you are curious how to create a table view with a Nib after you have subclassed UITableViewController WITHOUT a nib, here is how:
http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/TableView_iPhone/CreateConfigureTableView/CreateConfigureTableView.html#//apple_ref/doc/uid/TP40007451-CH6-SW10
Go to the paragraph right before "Creating a Table View Programmatically".
OK, when I did that, my landscape view of the "grid" looks filled up the entire space between the navigation bar at the top and the tab bar at the bottom just like I wanted.
I was fiddling with this some more and I found out that in my "non nib" version (the problematic one), I had set the table style to "grouped". When I changed it to "plain", it worked!!! But here is the thing though: In the nib version, "grouped" or "plain" gives the correct layout with the table occupying the whole space. So what gives?
Sorry for the long question but I guess what I am asking is:
1) How do you programmatically reset the size of the table view without introducing potential memory leaks or affecting other properties already set for you (ex: dataSource, delegate, autoResizeMask - these are set for you just because you subclassed UITableViewController)?
2) How do you do that for any view in general?
3) Why does "plain" style fill the layout as desired whereas "grouped" style gives the weird layout. Note that it this is not a problem in the Nib version.
Thanks for your patience!
Answer for (2), and hence for (1):
A UIView's frame is in a local coordinate system of its superview. A common way to make a view fit its superview is
CGRect bounds = [[self superview] bounds];
[self setFrame:bounds];
You should do this inside layoutSubviews.