UICollectionViewFlowLayout Size Warning When Rotat

问题:

We are using a UICollectionView to display cell that cover the full screen (minus the status and nav bar). The cell size is set from self.collectionView.bounds.size:

- (void)viewWillAppear:(BOOL)animated
{
    //
    // value isn't correct with the top bars until here
    //
    CGSize tmpSize = self.collectionView.bounds.size;
    _currentCellSize = CGSizeMake( (tmpSize.width), (tmpSize.height));
}

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout*)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {

    return _currentCellSize;
}

This sets the correct sizing for each device. Each cell is defined to have no insets, and the layout has no header or footer. However, when we rotate from portrait to landscape we get the following "complaint":

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.

Now I understand this error, however we reset the size of the cell and use the flow layouts built in rotation transition:

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    //self.collectionView.bounds are still the last size...not the new size here
}
- (void)didRotateFromInterfaceOrientation: UIInterfaceOrientation)fromInterfaceOrientation
{
    CGSize tmpSize = self.collectionView.bounds.size;
    _currentCellSize = CGSizeMake( (tmpSize.width), (tmpSize.height));
    [self.collectionView performBatchUpdates:nil completion:nil];//this will force the redraw/size of the cells.
}

The cells render correctly in landscape.

It seems as though the Flow Layout sees the old cell size (which causes the complaint since it will be too tall), but does read/render the new cell size set in didRotateFromInterfaceOrientation.

Is there a way to get rid of the complaint?

We've tried finding another hook during a device rotate transition that has access to the correct target screen size (vs the current screen size) with no luck. Debug output shows the complaint happens after willRotateToInterfaceOrientation but before didRotateFromInterfaceOrientation.

We've also verified the obvious; if we set up the cell height to be a fixed size less than the landscape screen height, the complaint doesn't occur. Also, the complaint does not occur when rotating from landscape back to portrait.

Everything runs fine, and renders correctly. However this complaint worries us. Anyone else have any ideas or solutions?

回答1:

I was getting the same warning. Unsatisfied with the "reloadData" approach, I found that calling [self.collectionView.collectionViewFlowLayout invalidateLayout] before setting the frame of the collection view silenced the warning and yielded the expected results.

回答2:

Not to throw another shrimp on this loaded, yet unaccepted, barbie.

- (CGSize)collectionView:(UICollectionView *)collectionView 
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {

    [collectionView setContentInset:UIEdgeInsetsMake(0, 0, 0, 0)];
    return CGSizeMake(100, collectionView.frame.size.height);
}

Setting the content insets just before returning the cell size did the trick for me.

Note:

I am using a container view in a storyboard to load the collection view within a UIViewController. I tried setting this on the flowLayout object in the storyboard. The collection view in the storyboard. And overriding one of the UICollectionViewDelegateFlowLayout; though I do not remember which one. I'm also not sure if this will work for a vertical layout.

回答3:

In

[UIViewController willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration]

I called the, [UICollectionViewLayout invalidateLayout] and seems to work good.

回答4:

I solved it.

You should just let the height of flowLayout less than collcetionView.frame.size.height.

 [flowLayout setItemSize:CGSizeMake(width, height)];


 collectionView.frame = CGRectMake(12, 380, 290, 80);

回答5:

A lot of the solutions suggest adding invalidateLayout to willAnimateRotationToInterfaceOrientation - but this is deprecated since iOS 8.

For iOS 8 and higher, use:

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

    [self.collectionView.collectionViewLayout invalidateLayout];
}

Thanks to @user7097242's comment here is a swift4 version:

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)
    self.collectionView.collectionViewLayout.invalidateLayout()
}

回答6:

I encountered this same issue. If the collection view was displayed when in portrait orientation, the cells would disappear when rotated to landscape. I did a combination of the other answers here to fix this.

I set my view (the one that contains the UICollectionView) up to receive the UIDeviceOrientationDidChangeNotification notification. In the method that responds to that notification, after the UICollectionView frame was adjusted, I did the following:

- (void)orientationChanged:(NSNotification *)notification
{
    CGSize size = (CGSize){self.frame.size.width - 2*kContentMargin, self.frame.size.height - 2*kContentMargin};
    [self.collectionView.collectionViewLayout setItemSize:size];

    [self.collectionView.collectionViewLayout invalidateLayout];
    [self.collectionView reloadData];
}

Note that the frame of the UICollectionView is being set automatically upon rotation because its resizingMask is set to this upon initialization:

self.collectionView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

回答7:

Just encountered and fixed the same problem. Since my solution is more along the lines you were asking for and doesn't match any existing answer, I've posted it here.

#define NUMBER_OF_CELLS_PER_ROW 1

- (UICollectionViewFlowLayout *)flowLayout {
    return (UICollectionViewFlowLayout *)self.collectionViewLayout;
}

- (CGSize)itemSizeInCurrentOrientation {
    CGFloat windowWidth = self.collectionView.window.bounds.size.width;

    CGFloat width = (windowWidth - (self.flowLayout.minimumInteritemSpacing * (NUMBER_OF_CELLS_PER_ROW - 1)) - self.flowLayout.sectionInset.left - self.flowLayout.sectionInset.right)/NUMBER_OF_CELLS_PER_ROW;

    CGFloat height = 80.0f;

   return CGSizeMake(width, height);
}

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [self.flowLayout invalidateLayout];
    self.flowLayout.itemSize = [self itemSizeInCurrentOrientation];
}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
    // Now that the rotation is complete, load the cells.
    [self.collectionView reloadData];
}

回答8:

This solved it for me:

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [self.collectionView.collectionViewLayout invalidateLayout];
}

And I am using this delegate method for setting the size:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

And I can from there use this with the correct frame after rotation:

self.collectionView.frame.size

回答9:

My fix was as simple as unchecking 'Adjust Scroll View Insets' for the view controller in IB, since I needed my navigation bar to be translucent.

回答10:

This works for me: (and hope it also works for you!)

- (void)viewWillLayoutSubviews 
{     
     self.flowLayout.itemSize = CGSizeMake(self.collectionView.bounds.size.width/4,self.collectionView.bounds.size.height);    
     [self.flowLayout invalidateLayout];
}

- (void)viewDidLayoutSubviews     
{
    self.flowLayout.itemSize = CGSizeMake(self.collectionView.bounds.size.width/4,self.collectionView.bounds.size.height); 
}

回答11:

I faced the same problem. here is how i solved it. hope it helps

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(    NSTimeInterval)duration
{
    [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];

    [self.collectionView reloadData];
}

回答12:

Try this...

UICollectionViewFlowLayout *layout = (id) self.collectionView.collectionViewLayout;

layout.itemSize = CGSizeMake(0.1, 0.1);

It's works for me.

回答13:

I ran into the same problem when resizing the frame of a UICollectionView. If I used the delegate method on FlowLayout to return the size of the cell (which would be updated based on the size of the containing UICollectionView), I would get the error message when I resized (smaller) the frame of the UICollectionView, since it didn't seem to ask the delegate for updated size information before complaining. It would eventually ask the delegate method for size info when redrawing, but it would still issue the warning at the time I assigned a new frame method. To get rid of the warning, I explicitly set the itemSize property of the UICollectionViewFlowLayout object before I set the frame to a new smaller value. My situation is simple enough that I think I can get away with doing the itemSize calculation at this point (since all my items in the collection view are the same size), instead of depending on the delegate method. Just setting the itemSize property while leaving the delegate method implemented did not solve the problem, as I think it ignored the value of itemSize if it detected that the delegate method was implemented (if it knows it is there, why doesn't it call it?!). Hopefully this helps - perhaps you can also explicitly set the itemSize before rotation.

回答14:

Just to suppress warning and (probably, not sure) improve performance you could before returning size in

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

check if view controller is in process of rotation and if it is return some relatively small size like CGSizeMake(0.1, 0.1)

回答15:

You can subclass UICollectionView and override setBounds:. There before calling [super setBounds:] the item size can be adjusted to the new bounds.
You should check whether the size of the bounds has changed, because setBounds: is invoked also while scrolling.

回答16:

Following code fixed it for me:

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return self.collectionView.frame.size;
}

回答17:

I've used an UICollectionViewFlowLayoutInvalidationContext, in which I calculate the new offset such that it maintains the same content offset. My own function collectionViewSizeForOrientation: returns the proper size. Its not perfect, but at least it's not sketchy:

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    CGSize fromCollectionViewSize = [self collectionViewSizeForOrientation:[self interfaceOrientation]];
    CGSize toCollectionViewSize = [self collectionViewSizeForOrientation:toInterfaceOrientation];

    CGFloat currentPage = [_collectionView contentOffset].x / [_collectionView bounds].size.width;
    NSInteger itemCount = [_collectionView numberOfItemsInSection:0];

    UICollectionViewFlowLayoutInvalidationContext *invalidationContext = [[UICollectionViewFlowLayoutInvalidationContext alloc] init];

    [invalidationContext setContentSizeAdjustment:CGSizeMake(toCollectionViewSize.width * itemCount - fromCollectionViewSize.width * itemCount, toCollectionViewSize.height - fromCollectionViewSize.height)];
    [invalidationContext setContentOffsetAdjustment:CGPointMake(currentPage * toCollectionViewSize.width - [_collectionView contentOffset].x, 0)];

    [[_collectionView collectionViewLayout] invalidateLayoutWithContext:invalidationContext];

    [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
}

collectionViewSizeForOrientation: in my case is the following, assuming that insets and item spacing are 0:

- (CGSize)collectionViewSizeForOrientation:(UIInterfaceOrientation)orientation
{
    CGSize screenSize = [[UIScreen mainScreen] bounds].size;

    CGFloat width = UIInterfaceOrientationIsLandscape(orientation) ? MAX(screenSize.width, screenSize.height) : MIN(screenSize.width, screenSize.height);
    CGFloat height = UIInterfaceOrientationIsLandscape(orientation) ? MIN(screenSize.width, screenSize.height) : MAX(screenSize.width, screenSize.height);

    return CGSizeMake(width, height);

}

回答18:

Trying to find a solution to silence these warnings on iOS 7 was proving difficult for me. I ended up resorting to subclassing my UICollectionView and added the following code.

- (void)setFrame:(CGRect)frame
{
    if (!iOS8 && (frame.size.width != self.frame.size.width))
    {
        [self.collectionViewLayout invalidateLayout];
    }

    [super setFrame:frame];
}

Some might want to do a whole size check with CGSizeEqualToSize().

回答19:

try at the end of didRotateFromInterfaceOrientation:

[self.collectionView setNeedsLayout]

if it does not work try to move all this stuff from didRotateFromInterfaceOrientation to willRotateToInterfaceOrientation

回答20:

Note: In my case, I discovered that we were setting the preferredContentSize property of the UIViewController in question. If you find this to be your case, you might have to deal with the following method of the UICollectionViewDelegateFlowLayout protocol:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    CGSize size = collectionViewLayout.collectionView.bounds.size;
    ...
    return size;
}

回答21:

I know this is an old question, but I just got the same problem and spent an hour to solve it. My problem was that, it seems the UICollectionView's frame size is always wrong (the height doesn't match the container) while I set the frame size right before the UICollectionView Flow layout delegate is called. So, I set the UICollectionView frame size again on the method :

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

And that did the trick. The height is now showing correctly and the warning is gone.