I have created a UICollectionView programmatically that will be displayed within a larger UIView. I've setup the delegate and datasource correctly, and it renders with no problem. However, when I increase the number of cells in the view to the point that scrolling is necessary to see the last row, I find that the UICollectionView is not able to scroll to the bottom. The last row is visible on the bounce, but is cut off when the bounce ends. Only about 10 pixels of a 75x75 pixel cell are visible, and there is no way past this.
I've tried increasing the content size, but that seems to have no affect. Is there something else I need to be doing to get the last row to display properly?
UPDATE: Perhaps a bit more details is in order...
My view setup looks like this: I have a paging-enabled UIScrollView that acts as my top-level UIView. Within this, I have created a series of UICollectionView objects. My UIScrollView is designed to scroll horizontally, while the UICollectionViews scroll vertically. I am accomplishing this using the RGMPagingScrollView library so I can benefit from reusable collection views to conserve memory.
As recommended, I took a look at implementing auto layout programmatically, but I am unclear as to exactly what to do. I've tried a couple different routes, but I end up with layout constraint errors. I also looked at the bounds and frame sizes for my collection views, and they appear to be correct. They end up being {{0, 0}, {320, 568}}, which I would expect for a full-screen collection view on my device.
I also took a look to see what the superview bounds/frame would be, but found that the superview for my UICollectionView was nil, which I did not expect since it is embedded within a UIScrollView. At this point, I'm at a loss as to what could be going on here. I've modified both the bounds and frame (shrinking the height by up to 200 px), thinking that might make a difference, but the behavior is the same.
This issue may also occur if minimumLineSpacing is being set for horizontal scrolling UICollectionViewFlowLayout.
Removing this worked for me.
You UICollectionView is probably going off screen. You can try autolayout to fix its size to its superview's size. You can also do it with autoresizing masks or overriding viewDidLayoutSubviews.
Related
I have a stack view that contains three UICollectionViews, set up to give each of them equal vertical space. That stack view is set to be the height of half of the display, so that it uses more space on larger devices. This has been set up in Interface Builder.
So, I need to set the cell size of the UICollectionView at runtime, since until we are running, I don't know what the actual size of the cells will be. I want them to be square, so I just want to take into account the height of the UICollectionView, subtract out the top and bottom section insets, and set the itemSize to the resulting size.
I attempt to do this in viewDidLayoutSubviews, since by then I figure that the initial heights of the collection views have been set. However, they appear to be set to 1000x1000 (even though they are a much more reasonable size in the storyboard), and so I compute a cell size based on a collection view height of 1000. This is too large, but I figure that I'll get called again and get another chance to recompute it. And I do, but not before UICollectionView complains loudly that the itemSize is incorrect (ie. too large to fit in the collectionView, which now has the "correct" size.)
What is the best way to get the behavior I'm looking for without the warnings from UICollectionView? Setting the collection view item size at runtime based on the eventual size of the UICollectionView is something I've struggled with in the past, and there never seems to be the "right" time to set the itemSize. I don't want to dynamically return it, if only because it's not something that changes during the life of the program. There just seems to be some inconsistencies that occur when laying out the views initially.
It seems odd to me that the collection view comes in with an initial size of 1000.0 by 1000.0, but I'm not sure how or why to fix that - perhaps it has something to do with being embedded in a stack view?
Edited to add: It is almost certainly the UIStackView that is causing the layout issues. I created a dummy project to test the size of a UICollectionView when it is the top level view vs embedded in a UIStackView. If it is not embedded, when viewDidLayoutSubviews is called, it has been properly sized to fit the bounds of its superview. However, if it is inside of a UIStackView, it stays at the default size of 1000x1000.
For now, I am working around this problem by adding the following code in viewDidLayoutSubviews:
if collectionView.bounds.size.width > view.bounds.size.width {
view.layoutIfNeeded()
}
Where collectionView is inside a UIStackView and view is the main view of the UIViewController. This allows all subsequent calculations based on the size of the view to be correct, and hopefully will not get called if the UIStackView behavior ever gets fixed.
Similar discussions here and here. Interesting point that in XCode8, the new default is to not save sizes of views in the XIB file, but instead bring everything in with an initial size of 1000x1000, to be resolved during the first layout pass. Except for UIStackViews, I guess.
Are you having sizeForItemAtIndexPath() return itemSize? I have found that implementing that function is the only reliable way to size a UICollectionViewCell dynamically at runtime.
I have a simple screen, with a slider and a label positioned next to each other horizontally. I have embedded these inside a UIScrollView (I set this to fill the screen and used 'Add missing constraints'), because I will need vertical scrolling later down the line. I don't however, want horizontal scrolling. I have seen numerous posts on here and other sources about people wanting to disable horizontal scrolling, however I'm not sure that's what I want to do, I think I need to restrict the UISlider from causing the horizontal scrolling; I think it is trying to take up more width than the screen. I have added what I think are the necessary horizontal constraints:
Leading space to container for the UISlider
Horizontal spacing to the UILabel, and
Trailing space to container for the UILabel
But this still causes horizontal scrolling, and the UISlider's are the cause, they are taking up more room than I want, as seen below:
I have tried disabling horizontal scrolling in the code using a few techniques, one being:
func scrollViewDidScroll(scrollView: UIScrollView) {
if scrollView.contentOffset.x>0 {
scrollView.contentOffset.x = 0
}
}
but this does not seem to stop the horizontal scrolling.
Can anyone offer any suggestions?
Thanks in advance.
My suggestion is to never use Add missing constraints. It never does what you really want.
Here's the problem. You are laying out your UI on a ViewController in the Storyboard that is square. Apple did this to remind you that you need to be flexible in your design, but it doesn't match the size of any device. When you Add missing constraints, it uses the absolute dimensions of that square to create the constraints which are certainly wrong.
In your specific case, it is giving the slider a width that is too wide, which is why the slider goes off the right side of your screen.
Here's the trick about scroll views. If the contents inside of a scroll view are wider than the scroll view itself, then that content will scroll. The same applies vertically: if the contents inside of a scroll view are taller than the scroll view, then the contents will scroll.
In order to design this to work on all phones, you need to make sure that the contents of the scroll view are laid out correctly for each phone size. Which certainly means you don't want to use specific widths for both the label and the slider because you'll end up with the wrong width for some device, if not all of them.
The best way to do this is to:
Drag out the scroll view and add it to your ViewController. Add constraints to make sure it is properly sized on all phones, such as attaching it on all sides to its superview with a fixed distance.
Drag out a new UIView and drop it on the scroll view. Drag its edges until it exactly matches the size of the scroll view. This will be your content view. Pin all four edges of this content view to the scroll view with offsets of 0.
Here's a tricky bit. Even though you've pinned the content view to the scroll view, its size of free to grow because that is what allows it to be bigger than the scroll view itself and allow there to be content to scroll over. To keep your scroll view from scrolling horizontally, you need to make sure the content view has the same width as the scroll view on all devices. To do that, find the scroll view and the content view in the Document Outline to the left of the Storyboard. Control-drag from the content view to the scroll view and select Equal Widths from the pop-up.
You still haven't told your content view how tall it should be. For now, give it an explicit height constraint of 1000. That will be enough to scroll.
Now, add your label and slider to the content view. In addition to constraining them to each other and to the edges of the content view, you will need to give your label a width constraint. Then Auto Layout will have all of the information it needs to compute the width of your slider. Auto Layout knows how wide the content view is (which will be different on different devices), it knows how wide your label is, and how far everything is from everything else, so it will just stretch the slider to fill in the rest.
If you do all of this, you will have a UI that is properly sized for all devices in all orientations that scrolls vertically.
Just embed all view in your UIScrollView in a UIView, give it the required constraints then the slider and label will stay.
That worked for me just now.
UIScrollView is special when you want use AutoLayout with it, subviews can not be added directly, it needs a container view to constraint the contentSize of UIScrollView, Auto Layout Guide:Working with Scroll Views explains the detail reason, and you can find many solutions to solve UIScrollView's auto layout on Google, Such as this answer.
To be honest, it's confused and complicated to understand UIScrollView's auto layout, but if you overcome this, others auto layout question is easy to resolve.
I know there are a couple of questions around but I could not figure out how to do this (none of the answers there helped me), so here is my version of the question.
I have an UICollectionView which is set to scroll horizontally. Each cell has an UIScrollView inside and inside the UIScrollView I have an UIImageView.
Now, the images displayed by the UIImageView are loaded from the internet and I can't figure out a way to make the zooming work correctly using storyboards and autolayout.
If I set constraints that tie my UIScrollView to it's container everything is ok. The moment I tie the UIImageView to the UIScrollView XCode starts to complain that the UIScrollView's size is ambiguous.
If I don't make any constraints in InterfaceBuilder the images are not the displayed in the correct size (doh!).
So, I'm stuck. I don't know what kind of constraints to make and which view needs to be tied to what. I know that my perfect world result is a view controller that behaves like the native iOS Photos app. That is, the image is displayed as large as the screen (with a black band at top and bottom or left & right depending on image's orientation) and that you can zoom it in and pan it around.
Help please!
Note
I did read these posts before posting my own question
UIScrollView zooming with Auto Layout
UIScrollView Zoom Does Not Work With Autolayout
“Pinch to Zoom” using AutoLayout
I don't know if it'll help you with your zooming problem but Apple provided a technical note about using scroll views with auto layout: Technical Note TN2154, UIScrollView And Autolayout
The important part with scroll views is, that the constraints of the subviews inside the scroll view are not bound to the scroll view itself, but to the scroll view's parent (in your case the collection view cell)
It works
You can easily do it. Well not really easily, i have been struggling for quite a while!
I managed to implement auto layout within the scrollable area. Just it is vertical only
Set intrinsic size to a "placeholder" (to scrollable view)
Don't set contentSize at all
Attach right constraints to the wrapper (so it will be relative to the parent view)
self.view.addConstraint(NSLayoutConstraint(
item:self.view, attribute:.Trailing,
relatedBy:.Equal, toItem:contentView,
attribute:.Trailing, multiplier:1, constant:0))
scrollView.setTranslatesAutoresizingMaskIntoConstraints(false)
So, in your case, your contentView right side should be attached the right side of the image
Try it out, certainly you will have your zooming to work
Here is an example, it may help you
https://github.com/nchanged/swift-content-manager/tree/master
I am having a very frustrating issue. I know there are all kinds of issues with UIScrollView in iOS7 and XCode 5. I need to implement a scrollview and there are all kinds of tutorials showing you how to do it by switching off auto layout but that then messes with the rest of the views in my app.
I tried the fix of putting my subviews into a container UIView and placing that in the UIScrollView and setting the scrollview's content size to the size of the contained UIVIew. That didn't work. Now I am working with placing everything in the scrollview and it all works with one exception. When I load the view on the simulator or a device the content view is moved down but somewhere around 60 points or so. See image below.
That white space below the title bar on the right is still the scroll view as I can press and drag within it. Adjusting the contentOffset doesn't do any good as that just scrolls the view down slightly. I have no idea what to do here.
Just a little more info: I setup the scrollview and all the subviews in storyboard and the connected them up. Not sure if that has any bearing on it.
Thanks in advance for any help you can provide.
I think your Scrollview top space constraint have 64 pixels. That's a problem. So, set your top space constraint value to 0.
You need to add the constraints before view displayed then contentsize will be set automatically.
Check UIScrollView's autoresizing mask. It has to be set like this.
I have been struggling with this for a few days now, and I am looking to see if someone can help me with this AutoLayout problem.
In my iOS7 application, I have a UIView that has a UIScrollView and inside it a UIView(container) with some elements positioned. I have in there, a UIImageView, UITableView, UICollectionView, UITextView and a MapView. There is no height constraint on the UIScrollView and the container UIView. There are no height constraints on the UICollectionView and the UITextView.
What I want to accomplish is
The UITextview should expand to the content size as in all the text should appear without any vertical scrolling enabled for the UITextView.
The UICollectionView should always show all items and there should not be any scrolling enabled there as well.
Overall, I want a UIScrollView with items in it, that scale based on content. I have tried numerous things, but failed.
If anyone has pointers or suggestions on how to go about doing this, it would be very helpful.
OK, I would go about this in a completely different way.
First, get rid of the scrollView completely.
Just use a UICollectionView for this entire interface.
The UICollectionView can take a UIView for a section header. Make this UIView with your UITextView inside. You will need to manually calculate the correct height for your UITextView (and UIView).
Something like...
CGSize size = [theText sizeWithFont:<the font used> constrainedToSize:CGSizeMake(desiredWidth, CGFLOAT_MAX)];
Then just populate your collection view.
By doing this your collection view will control all the scrolling. Because you have set the textview to the correct size in the header you will have all the text there.
This is how I would go about it:
I assume your issue is with the height of the views, that affect the scrolling.
In the textViewDidChange: I would set the frame of the UITextView same as it's contentSize. When they are both the same, scrolling gets disabled.
After populating your UITableView and calling reloadData, I would set it's frame same as it's contentSize.
The mapView (MKMapView, I suppose) has the same frame throughout, I suppose. So you just use it's fixed height. If it changes height, you must store it's changing height each time it changes.
Once you have all the heights, add them up, and set the frame of the outer view same as then combined height of the inner view. Iterate this to all nested views, beginning from innermost views, and moving to outer views.
The catch here is, every time your content changes, the frames have to be resized. Hence changing the frames in textViewDidChange:, after reloadData, etc makes sense.
EDIT : One thing you might want to do first is, getting rid of redundant views. Your view hierarchy seems Rube Goldberg to me. The lesser views you have, the lesser work you will have to do.
Ok.. so I solved this problem by creating a IBOutlet for my NSLayoutConstraint on the UITextView in question.
I simply computed the height and then applied it on the constraint and it worked..
#Fogmeister - Your solution will also work, but it would require me to rewire a whole UI page.. Your approach is definitely a feasible one and shall keep in mind for future iOS apps..