My problem: Find a way, such that when a button is pressed a new colleciton view cell is inserted by an animation of it sliding in from the right side of the screen.
As of right now, I have a button in my view, when it is clicked, adds a new object to my model, then calls reloadData and the new cells just appears on the screen. All I am struggling with is the animation. Any help would be very much appreciated.
Thanks
If you want the cells to animate, you could set a property shouldAnimate = YES.
Then in your collectionView:cellForItemAtIndexPath: check that property and apply the animation if needed (or remove it).
After setting the property, reload only the visibleCells: [collectionView reloadItemsAtIndexPaths:collectionView.indexPathsForVisibleItems].
Now, since the animation is provided when a cell is requested through the Datasource-Protocol, you also get the animation when you scroll.
Related
I have an NSCollectionView with a vertical NSCollectionViewFlowLayout. I display rectangular icons in it.
I also have a slider in the UI, and when that changes, I adjust the minItemSize, which I then use in collectionView:itemForRepresentedObjectAtIndexPath: to create an equally sized NSImageView to the returned NSCollectionViewItem's imageView. Then I reload the view by invoking reloadData.
After that, the view shows the icons in the new size as intended.
The problem is, provided I have more data to show than fits into the current scoll view, that when the General System Preferences are set to Show scroll bars: When scrolling, the scrollbar disappears after reloading the collection view, and trying to scroll with the trackpad leads to a bounce that's telling me that the scroll view thinks that the content is just what's visible, nothing more to scroll.
But as soon as I resize the window, which also resizes the collection view inside, the scrollbars come back.
Curiously, if the System Prefs are set to Show scroll bars: Always, then the issue does not appear and the scrolling always works, and the scrollbars always remain visible.
I've tried a lot of things to trigger the re-calculation of the scroll view, such as invalidating the layout of the collection view's layout, the scroll view itself, its content view, and also tried to set their needsLayout to true. Nothing makes this work.
Update: The potential duplicate (NSCollectionView does not scroll items past initial visible rect), neither the collectionView.setFrameSize: nor the window.setFrame: suggestions work for my case (I tried adding these line before and after reloadData).
Even if I force a resize of the window like this, it doesn't bring the scrollbars back, only a manual dragging of the window edges does:
[self.collectionView.window setFrame:NSInsetRect(self.view.window.frame, 1, 1) display:YES];
Also note that in my case, initially the scrolling works, just not after resizing and reloading.
Another finding: When I call selectItemsAtIndexPaths:scrollPosition: after reloadData, then the scrollbar comes back. But only if I pass a non-empty NSSet for the paths. And since I may not have selected any items, this isn't a permanent solution.
If no other ideas come up, I'll try to make a demo project.
I've solved it:
I had to delay the call to reloadData, e.g. by calling it from within the block code of dispatch_async(dispatch_get_main_queue(), ^{ ... });
Before the fix, I did call reloadData right from the setSliderValue: handler, which is bound to the slider's value. It appears that this didn't go well together.
I have a collection view that is 100 points wide with a number of cells that are each also 100 points wide. I've got it setup to support scrolling and paging horizontally so the user can flick left and right and each cell occupies the entire collection view frame.
Originally, I had no scrolling and the user would tap each cell to activate something in the app. Now that its a narrow frame where only one cell can be seen at a time I feel that tapping is redundant and the cell should simply be tapped in effect when it comes in view.
Is there a way to trigger an event such as didSelectItemAtIndexPath when a given UICollectionViewCell becomes the one displayed within my collection view's frame?
UICollectionView responds to selectItemAtIndexPath:animated:scrollPosition:.
It also responds to indexPathsForVisibleItems which will be useful to determine where to make the selection.
You also need to decide when to make the selection, probably best after receiving scrollViewDidEndDecelerating: which the delegate inherits from UIScrollViewDelegate).
But it may be even better advice to look at what your code does upon selection and just do that (launched from the same place in code, probably when scrolling is finished), leaving selection out of it.
I'm trying to figure out a way to keep a UICollectionViewCell from being removed (didEndDisplayingCell) from my UICollectionView when its original scroll position scrolls off of the view. I know this is the way a UICollectionView is supposed to work, that cells are removed and returned to the reuse pool when they are no longer visible, but this is based on their original position in the UICollectionView. I'm trying to drag that cell past the original visible area into a further away location, but it gets removed killing the pan gesture in progress and killing its view in the collection view once its original position is scrolled out of view. Is there a way to override this behavior and hold onto a UICollectionViewCell until I'm done with it?
I've seen the other ways to attack this problem by creating an image of the cell and dragging that instead, but that won't satisfy my purposes. I need the original cell to survive beyond its original screen position as I scroll through the UICollectionView.
Make copy when dragging your cell around and hide original cell.
I am working on an app having a collection view with Collection view cells having 4 buttons to invoke different actions.Each links to a different IBAction. I have read multiple threads across the board and had decided to use storyboards rather than go at it programmatically since 'this could be the way forward'. So while setting up the buttons, I had set default label text to Button 1, Button 2 etc. In the code, while giving cell for index path, I am changing the button text to something programmatically. When the application is run the cells render fine with dequeueing, and the text being set programmatically is set correctly. However, when I click any of the buttons, the action is called, but the label text of the button resets to what was set using storyboards.
I have tried everything to retain the text label copy to what it should be. But to no avail. When I again dequeue the cell by scrolling across the collection view and the view gets redrawn, the button again gets the correct text.
Can anyone please shed some light on why the button text for a button placed in a collection cell will reset its text and will not allow it to be set unless the view is redrawn.. Also any ideas on how to fix this.
Thanks a ton
deej nailed it --
I had the same problem but was doing something stupid:
self.btnProperty.titleLabel.text = #"button title";
rather than:
[self.btnProperty setTitle:#"button title" forState:UIControlStateNormal];
Use the latter.
I'm trying to achieve an effect wherein as a tableview is scrolling, the currently visible cells will animate according to where they are positioned on the screen. I'm somewhat new to IOS dev, so let me try to break it down:
Tableview loads with custom cells User begins scrolling While the
table is in motion, the visible cells have a UIView in which I would
like to perform an animation that corresponds directly to the cell's
current Y position on the screen.
Cells will ONLY animate when they
are visible
Cell animation directly corresponds to table motion, i.e.
whenever the table view scrolls, the cells are animating; once the
table stops, the animations pause
One solution I have thought of is to update drawRect every single frame when the tableview is moving. Depending on the graphic operations, this could be horrible performance wise. Is there a way to grab the current table position every time it changes? Would I be better suited to use Core Animation?
This might be helpful if you want to achieve something like below:
https://github.com/mrugrajsinh/AnimatedTableViewCellDemo
Make your view controllers the delegate of the UITableView, and use all the methods of scrollview Delegate also. There you have many controls for start scrolling and end scrolling, and within thpse controls you could check for uitableview cell positioning.
You have to become delegate to this: https://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UITableViewDelegate_Protocol/Reference/Reference.html
and this is the method to override and animate your cells:
– tableView:willDisplayCell:forRowAtIndexPath: