I have a collection view. When I toggle the in-call status bar, my collection view items disappear when the green "you are on a call" status bar is visible. They return when I dismiss the bar.
The log spits out this: "The behavior of the UICollectionViewFlowLayout is not defined because the item height must be less that the height of the UICollectionView minus the section insets top and bottom values."
Has anyone encountered this, and how have you gotten around it? I am using sizeForItemAtIndexPath as follows:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return self.collectionView.frame.size;
}
Should I be using something else to specify the size of each item?
For anyone else that experiences this. This is the right way to define the item size:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return self.collectionView.frame.size;
}
You could probably also set itemSize on the collectionViewLayout, but the key to making the items stick around, and not disappear when on a phone call, is to reload the collection view in viewDidLayoutSubviews:
[self.collectionView reloadData];
Related
There's this bug happening when I drag a UICollectionViewCell outside of the frame of the collection: the collection's contentOffset is reset to 0, I suppose to scroll to top, even when dragging the cell over below the collection. The problem is the contentOffset has to be manually put back to where it was before and that's visually delayed.
I've tried locking the scroll while dragging, such as the following
- (void)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout willBeginDraggingItemAtIndexPath:(NSIndexPath *)indexPath {
collectionView.scrollEnabled = NO;
}
- (void)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout didEndDraggingItemAtIndexPath:(NSIndexPath *)indexPath {
collectionView.scrollEnabled = YES;
}
and it didn't do anything, contentOffset still changes. Also did the following
- (CGPoint)collectionView:(UICollectionView *)collectionView targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset {
if (proposedContentOffset.y > -10.0f) { // Minimum scroll from top is -10
return CGPointMake(proposedContentOffset.x, -10.0f);
}
return proposedContentOffset;
}
- (void)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout willEndDraggingItemAtIndexPath:(NSIndexPath *)indexPath {
if (collectionView.contentOffset.y > -10.0f) { // Minimum scroll from top is -10
[collectionView setContentOffset:CGPointMake(collectionView.contentOffset.x, -10.0f)];
}
}
to reset the contentOffset whenever it changes and this works fine, but the contentOffset is changed while dragging and the reset only happens when the user releases the cell, so there's a delay. Can I, somehow, lock the contentOffset while dragging?
I think it's worth mentioning my view structure is currently
UIScrollView
UICollectionView
UICollectionView (the one that has drag-drop enabled)
The parent ScrollView unifies both scrolls of the collections inside, so that could be a problem. When the collection is scrolled to top by the contentOffset, it slightly invades the collection above it.
I realised the project was using the LXReorderableCollectionViewFlowLayout framework for drag and drop on UICollectionViews, so I inspected that source code and found that the method that treats dragging out of the collection is
- (void)handleScroll:(NSTimer *)timer
so I added a little check on case LXScrollingDirectionUp to have a maximum edge offset, that I set as a property of that class, like the following
// distance calculated above: how much to scroll based on drag action
if (distance + contentOffset.y > _maxScrollingEdgeOffset.top) {
distance = 0;
}
And that fixed it!
I have collection view with cells I'm presenting horizontally + paging enabled. However I have above cell space that I cant remove (green on screenshot - collection view background). Size of cell is same as containers frame. For better understanding what I mean check screenshot. Any ideas? Thank you very much.
automaticallyAdjustsScrollViewInsets doesn't works for me
[self.calendarView setContentInset:UIEdgeInsetsMake(-64, 0, 0, 0)]; works but I don't know how to get these -64 programatically.
Did you try to implement these methods below and set zero insets and spacings?
You also need to check if the size of the cell is appropriate, may be the way you see the top spacing is the only way layout engine can put the cell. Please, check what size is set as expected
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
return UIEdgeInsetsZero;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView
layout:(UICollectionViewLayout *)collectionViewLayout
minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
return 0.0;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView
layout:(UICollectionViewLayout *)collectionViewLayout
minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
return 0.0;
}
I've came across similar issue many times.
When a UIScrollView or its subclass, e.g. UITableView and UICollectionView, is the first child of viewController.view, it will get a unexpected contentInset.
My solution:
If there are other siblings of UIScrollView, make one of
non-UIScrollView as first child.
If there is no other siblings, add a dummy UIView as the first child, and either hide the UIView or set the height to 0
In my UICollectionView I have a cell that should take the entire width of the device. Here is how I set the size for the item:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(self.view.bounds.size.width, 120);
}
I have found that on rotation, the width of the cell does not change. I can resolve this using [collectionView.collectionViewLayout invalidateLayout] in didRotateFromInterfaceOrientation: but this isn't satisfactory. What if the user rotates while in another screen in my app? I will need to add the same to viewWillAppear. What about if the rotation occurs while the app is backgrounded? Now I need to add it for the UIApplicationDidBecomeActiveNotification notification.
What confuses me most is that this is not required for my custom headers in the same collection view. The following supplementary views correctly re-size on orientation change:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
return CGSizeMake(self.view.bounds.size.width, 40);
}
Where am I going wrong? What should I do to have the cells re-size automatically to fill the width of the collection view?
A bit late I know but could you solve this by subclassing flow layout and adding?
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
return TRUE;
}
I want to display several cells in a UICollectionView in this manner: each cell is like a page to user, and an active UICollectionViewCell should occupy the full bound of the UICollectionView.
However for some reasons, there is black gap between cells after scrolling right.
Why does it happen?
I have already defined this function to control the size of "page" view:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
// the size is half of the screen
return CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height/2.0);
}
Looks like you need to set minSpacing to 0.
This sets the minimum gap between each item and also between the items and the edge of the collection view.
http://postimg.org/image/6bws3catp/
As you can see on the image I need something that gives me the possibility of resizing a cell depending on the length of the text that contains.
I' ve been trying to do that with a UICollectionview but the cells have always the same size and if I try to alterate the size playing with the frame.size and location parameters the scroll gets crazy.
Maybe the UICollectionView isn't the best choice...
Thank you very much
EDIT:
Because of your answers my cells are able to change dynamically their size but the margins aren't behaving as I expected.
The margins of the cells depends always on the biggest cell of the same row
http://postimg.org/image/3scthf9rv/
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{
return 6;
}
I have implement this to set my margin value between cells in 6 points, but maybe this only works when you have one cell in each row in a vertical collection view..
Thank you again for all your help
You can check out https://github.com/bryceredd/RFQuiltLayout . Looks
like something you can use for this...
you can override the following method and return a CGSize object that specifies the size you want to use for each cell. Using this method, you can actually have each cell be a different size:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
Example:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return CGSizeMake(100, 100);
}
Your view controller needs to be a delegate of UICollectionViewDelegateFlowLayout in order for this method to be called. So don't forget to add that delegate declaration to your view controller's .h file, such as:
#interface MyViewController () <UICollectionViewDelegateFlowLayout>
UICollectionView is the correct choice. You just need to customise the flow layout attributes.
Read Customizing the Flow Layout Attributes
Specifically you would need to implement Collection View Delegate method:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
// In this method you can calculate the size of the string for each cell
UIFont *font = // font to create the text for each cell
NSString *string = // text string for each cell
CGSize size = [string sizeWithFont];
return size;
}