uicollectionview

问题 I have a UICollectionView and I simply want it to show up. I have the delegate and datasource attached to the file's owner in the interface builder. collectionView:numberOfItemsInSection: Gets called just fine. I have been messing with this for a few hours and just can't figure it out... Any help would be great, Thanks in advance! Here is the full source. Sorry if its kinda messy. .h File #import <UIKit/UIKit.h> #import <MapKit/MapKit.h> #import "PinAnnotation.h" #import "Jot.h" @interface

问题 I have a UICollectionViewCell subclass. I wrote an updateConstraints method as I've done a hundred times before. For some reason that is never called when the cell is dequeued. I had to add a manual call to [cell setNeedsUpdateConstraints] after dequeueing it. Any idea what could be going on here? 回答1: Implement this method and return YES. This could probably help. + (BOOL)requiresConstraintBasedLayout For details: https://stackoverflow.com/a/23616469/1300262 来源： https://stackoverflow.com

问题 I originally tried doing this with two UICollectionViews stacked on top of each other. However getting it to scale right was nightmare with Auto-layout (I'm a novice iOS developer so that is more a critique of my skill than Auto-layou t). I'd like to stack two sections of UICollectionView cells on top of each other like this: +----------------------+ |+-Section 0---------->| | +-------+ +-------+ | | | | | | | | | | | | | | |Cell 0 | |Cell 1 |+-> | | | | | | | | | | | | | +-------+ +-------+

问题 I originally tried doing this with two UICollectionViews stacked on top of each other. However getting it to scale right was nightmare with Auto-layout (I'm a novice iOS developer so that is more a critique of my skill than Auto-layou t). I'd like to stack two sections of UICollectionView cells on top of each other like this: +----------------------+ |+-Section 0---------->| | +-------+ +-------+ | | | | | | | | | | | | | | |Cell 0 | |Cell 1 |+-> | | | | | | | | | | | | | +-------+ +-------+

问题 I have a CollectionView which displays images to the user. I download these in the background, and when the download is complete I call the following func to update the collectionViewCell and display the image. func handlePhotoDownloadCompletion(notification : NSNotification) { let userInfo:Dictionary<String,String!> = notification.userInfo as! Dictionary<String,String!> let id = userInfo["id"] let index = users_cities.indexOf({$0.id == id}) if index != nil { let indexPath = NSIndexPath

问题 I see this error in my logs and I don't know what it means: PAC Fetch failed with error [NSURLErrorDomain:-1003] 2017-06-08 17:07:56.157874+0200 xxxxxx[27059:7093559] [] nw_proxy_resolver_create_parsed_array PAC evaluation error: NSURLErrorDomain: -1003 At the same time I have a problem with a collectionView in my app. Don't know if it's related to the error or not: Sometimes, and only if the app is used in one remote office of our Company, both with the simulator and a real device, a

问题 I was browsing the documentations, when I started wondering if "beginUpdates" in a UITableView and "performBatchUpdates" in a UICollectionView have the same behavior. If so, is there a reason, that they're called differently, even though they're virtually the same thing? Thanks! 回答1: UITableView 's beginUpdates must be matched with a call to endUpdates . UICollectionView 's performBatchUpdates:completion method does not require you to call back to the collection view when you are doing with

问题 I was browsing the documentations, when I started wondering if "beginUpdates" in a UITableView and "performBatchUpdates" in a UICollectionView have the same behavior. If so, is there a reason, that they're called differently, even though they're virtually the same thing? Thanks! 回答1: UITableView 's beginUpdates must be matched with a call to endUpdates . UICollectionView 's performBatchUpdates:completion method does not require you to call back to the collection view when you are doing with

问题 I have UICollectionView, i am selected cell with didSelectItemAt and deselect with didDeselectItemAt but selected cells are replaced https://im4.ezgif.com/tmp/ezgif-4-2715e62591.gif func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { let cell = collectionView.cellForItem(at: indexPath) // print(indexPath) let collectionActive: UIImageView = { let image=UIImageView(image: #imageLiteral(resourceName: "collectionActive")) image.contentMode =

问题 I have 3 view controllers called firstvc , secondvc , thirdvc . And I have one collection view which will scroll horizontally. I have done that. And if I select any cell, it will print which index path it was. It's fine, no problem. So in my mainviewcontroller I have one collection view which will scroll horizontally. And there is one UIView called myview . Whenever I press any cell, I get its indexPath . I need to show my 3 view controllers as subviews of myview in my mainviewcontroller . My