版本记录

前言

2017年iOS版本更新到了11.0的系统，新机器比如iPhone X都是预装11.0的系统，而我们的UIKit框架中的UICollectionView类都做了哪些更改?接下来我们就看一下iOS11.0中UICollectionView类的改变，很多处新增，改动的还是很大的，下面我们就详细的看一下。由于前面几篇写了UITableView新增，里面已经详细的介绍了新增的内容，所以这里UICollectionView只列出来了改变的内容，不具体说明使用方法，感兴趣的可以参考。
1. 浅谈iOS 11.0中UITableView 都更改了什么？ （一）
2. 浅谈iOS 11.0中UITableView 都更改了什么？ （二）
3. 浅谈iOS 11.0中UITableView 都更改了什么？ （三）

@property (nonatomic, weak, nullable) id <UICollectionViewDragDelegate> dragDelegate

@property (nonatomic, weak, nullable) id <UICollectionViewDragDelegate> dragDelegate API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

@property (nonatomic, weak, nullable) id <UICollectionViewDropDelegate> dropDelegate

@property (nonatomic, weak, nullable) id <UICollectionViewDropDelegate> dropDelegate API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

@property (nonatomic) BOOL dragInteractionEnabled

/* To enable intra-app drags on iPhone, set this to YES.
 * You can also force drags to be disabled for this collection view by setting this to NO.
 * By default, For iPad this will return YES and iPhone will return NO.
 */
@property (nonatomic) BOOL dragInteractionEnabled API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

@property (nonatomic) UICollectionViewReorderingCadence reorderingCadence

/* Reordering cadence affects how easily reordering occurs while dragging around a reorder-capable drop destination.
 * Default is UICollectionViewReorderingCadenceImmediate.
 */
@property (nonatomic) UICollectionViewReorderingCadence reorderingCadence API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

@property (nonatomic, readonly) BOOL hasUncommittedUpdates

// Returns YES if the collection view is reordering or has drop placeholders.
@property (nonatomic, readonly) BOOL hasUncommittedUpdates API_AVAILABLE(ios(11.0));

@property (nonatomic, readonly) BOOL hasActiveDrag

/* YES if a drag session is currently active. A drag session begins after items are "lifted" from the collection view.
 */
@property (nonatomic, readonly) BOOL hasActiveDrag API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

@property (nonatomic, readonly) BOOL hasActiveDrop

/* YES if collection view is currently tracking a drop session.
 */
@property (nonatomic, readonly) BOOL hasActiveDrop API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

代理UICollectionViewDragDelegate

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@protocol UICollectionViewDragDelegate <NSObject>

@required

/* Provide items to begin a drag associated with a given indexPath.
 * If an empty array is returned a drag session will not begin.
 */
- (NSArray<UIDragItem *> *)collectionView:(UICollectionView *)collectionView itemsForBeginningDragSession:(id<UIDragSession>)session atIndexPath:(NSIndexPath *)indexPath;

@optional

/* Called to request items to add to an existing drag session in response to the add item gesture.
 * You can use the provided point (in the collection view's coordinate space) to do additional hit testing if desired.
 * If not implemented, or if an empty array is returned, no items will be added to the drag and the gesture
 * will be handled normally.
 */
- (NSArray<UIDragItem *> *)collectionView:(UICollectionView *)collectionView itemsForAddingToDragSession:(id<UIDragSession>)session atIndexPath:(NSIndexPath *)indexPath point:(CGPoint)point;

/* Allows customization of the preview used for the item being lifted from or cancelling back to the collection view.
 * If not implemented or if nil is returned, the entire cell will be used for the preview.
 */
- (nullable UIDragPreviewParameters *)collectionView:(UICollectionView *)collectionView dragPreviewParametersForItemAtIndexPath:(NSIndexPath *)indexPath;

/* Called after the lift animation has completed to signal the start of a drag session.
 * This call will always be balanced with a corresponding call to -collectionView:dragSessionDidEnd:
 */
- (void)collectionView:(UICollectionView *)collectionView dragSessionWillBegin:(id<UIDragSession>)session;

/* Called to signal the end of the drag session.
 */
- (void)collectionView:(UICollectionView *)collectionView dragSessionDidEnd:(id<UIDragSession>)session;


/* Controls whether move operations (see UICollectionViewDropProposal.operation) are allowed for the drag session.
 * If not implemented this will default to YES.
 */
- (BOOL)collectionView:(UICollectionView *)collectionView dragSessionAllowsMoveOperation:(id<UIDragSession>)session;

/* Controls whether the drag session is restricted to the source application.
 * If YES the current drag session will not be permitted to drop into another application.
 * If not implemented this will default to NO.
 */
- (BOOL)collectionView:(UICollectionView *)collectionView dragSessionIsRestrictedToDraggingApplication:(id<UIDragSession>)session;

@end

代理UICollectionViewDropDelegate

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@protocol UICollectionViewDropDelegate <NSObject>

@required

/* Called when the user initiates the drop.
 * Use the dropCoordinator to specify how you wish to animate the dropSession's items into their final position as
 * well as update the collection view's data source with data retrieved from the dropped items.
 * If the supplied method does nothing, default drop animations will be supplied and the collection view will
 * revert back to its initial pre-drop session state.
 */
- (void)collectionView:(UICollectionView *)collectionView performDropWithCoordinator:(id<UICollectionViewDropCoordinator>)coordinator;

@optional

/* If NO is returned no further delegate methods will be called for this drop session.
 * If not implemented, a default value of YES is assumed.
 */
- (BOOL)collectionView:(UICollectionView *)collectionView canHandleDropSession:(id<UIDropSession>)session;

/* Called when the drop session begins tracking in the collection view's coordinate space.
 */
- (void)collectionView:(UICollectionView *)collectionView dropSessionDidEnter:(id<UIDropSession>)session;

/* Called frequently while the drop session being tracked inside the collection view's coordinate space.
 * When the drop is at the end of a section, the destination index path passed will be for a item that does not yet exist (equal
 * to the number of items in that section), where an inserted item would append to the end of the section.
 * The destination index path may be nil in some circumstances (e.g. when dragging over empty space where there are no cells).
 * Note that in some cases your proposal may not be allowed and the system will enforce a different proposal.
 * You may perform your own hit testing via -[UIDropSession locationInView]
 */
- (UICollectionViewDropProposal *)collectionView:(UICollectionView *)collectionView dropSessionDidUpdate:(id<UIDropSession>)session withDestinationIndexPath:(nullable NSIndexPath *)destinationIndexPath;

/* Called when the drop session is no longer being tracked inside the collection view's coordinate space.
 */
- (void)collectionView:(UICollectionView *)collectionView dropSessionDidExit:(id<UIDropSession>)session;

/* Called when the drop session completed, regardless of outcome. Useful for performing any cleanup.
 */
- (void)collectionView:(UICollectionView *)collectionView dropSessionDidEnd:(id<UIDropSession>)session;

/* Allows customization of the preview used for the item being dropped.
 * If not implemented or if nil is returned, the entire cell will be used for the preview.
 *
 * This will be called as needed when animating drops via -[UICollectionViewDropCoordinator dropItem:toItemAtIndexPath:]
 * (to customize placeholder drops, please see UICollectionViewDropPlaceholder.previewParametersProvider)
 */
- (nullable UIDragPreviewParameters *)collectionView:(UICollectionView *)collectionView dropPreviewParametersForItemAtIndexPath:(NSIndexPath *)indexPath;

@end

枚举UICollectionViewDropIntent

typedef NS_ENUM(NSInteger, UICollectionViewDropIntent) {
    /* Collection view will accept the drop, but the location is not yet known and will be determined later.
     * Will not open a gap. You may wish to provide some visual treatment to communicate this to the user.
     */
    UICollectionViewDropIntentUnspecified,
    
    /* The drop will be placed in item(s) inserted at the destination index path.
     * Opens a gap at the specified location simulating the final dropped layout.
     */
    UICollectionViewDropIntentInsertAtDestinationIndexPath,
    
    /* The drop will be placed inside the item at the destination index path (e.g. the item is a container of other items).
     * Will not open a gap. Collection view will highlight the item at the destination index path.
     */
    UICollectionViewDropIntentInsertIntoDestinationIndexPath,
    
} API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

类UICollectionViewDropProposal

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@interface UICollectionViewDropProposal : UIDropProposal

- (instancetype)initWithDropOperation:(UIDropOperation)operation intent:(UICollectionViewDropIntent)intent;

/* The default is UICollectionViewDropIntentUnspecified.
 */
@property (nonatomic, readonly) UICollectionViewDropIntent intent;

@end

协议UICollectionViewDropCoordinator

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@protocol UICollectionViewDropCoordinator <NSObject>

/* Ordered list of items available for this drop.
 */
@property (nonatomic, readonly) NSArray<id<UICollectionViewDropItem>> *items;

/* The last hit-tested index path known during the drop session.
 * If this is nil, the proposal's intent will be .unspecified
 */
@property (nonatomic, readonly, nullable) NSIndexPath *destinationIndexPath;

/* The current drop proposal at the time of the drop.
 */
@property (nonatomic, readonly) UICollectionViewDropProposal *proposal;


@property (nonatomic, readonly) id<UIDropSession> session;

/* Animate the dragItem to an automatically inserted placeholder item.
 *
 * A placeholder cell will be created for the reuse identifier and inserted at the specified indexPath without requiring a dataSource update.
 *
 * The cellUpdateHandler will be called whenever the placeholder cell becomes visible; -collectionView:cellForItemAtIndexPath: will not be called
 * for the placeholder.
 *
 * Once the dragItem data is available, you can exchange the temporary placeholder cell with the final cell using
 * the placeholder context method -commitInsertionWithDataSourceUpdates:
 *
 * UICollectionViewDropPlaceholderContext also conforms to UIDragAnimating to allow adding alongside animations and completion handlers.
 */
- (id<UICollectionViewDropPlaceholderContext>)dropItem:(UIDragItem *)dragItem toPlaceholder:(UICollectionViewDropPlaceholder*)placeholder;

/* Animate the dragItem to a newly inserted item at the specified index path.
 * You must call -performBatchUpdates:completion: to update your data source and insert a new item into the collection view prior to calling this method.
 *
 * To tweak the appearance of the preview being dropping (e.g. supply a clipping path), see -collectionView:dropPreviewParametersForItemAtIndexPath:
 */
- (id<UIDragAnimating>)dropItem:(UIDragItem *)dragItem toItemAtIndexPath:(NSIndexPath *)indexPath;

/* Animate the dragItem to a rect inside an existing item.
 * The rect is in the coordinate space of the cell at this index path.
 * The item will be animated with an aspect fit scale transform to fit inside the rect. Use a rect with zero size to shrink the item to a single point.
 */
- (id<UIDragAnimating>)dropItem:(UIDragItem *)dragItem intoItemAtIndexPath:(NSIndexPath *)indexPath rect:(CGRect)rect;

/* Animate the dragItem to a location specified by the UIDragPreviewTarget.
 */
- (id<UIDragAnimating>)dropItem:(UIDragItem *)dragItem toTarget:(UIDragPreviewTarget *)target;

@end

类UICollectionViewDropPlaceholder

UIKIT_EXTERN API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos,watchos)
@interface UICollectionViewDropPlaceholder : UICollectionViewPlaceholder

/* If specified, will be used to modify the appearance (e.g. visiblePath to supply a "cut out" region of the placeholder cell) of the animating dropped item.
 * Handler will be called as-needed.
 */
@property (nonatomic, nullable, copy) UIDragPreviewParameters * _Nullable (^previewParametersProvider)(__kindof UICollectionViewCell *);
@end

协议UICollectionViewDropItem

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@protocol UICollectionViewDropItem <NSObject>

@property (nonatomic, readonly) UIDragItem *dragItem;

/* If this drop item is also from this collection view this indexPath will specify the location of the item.
 * If the dragItem comes from some other source (e.g. another source inside or outside of the app), it will be nil.
 * This is useful for directly accessing the model objects in the data source instead of using the item provider
 * to retrieve the data.
 */
@property (nonatomic, readonly, nullable) NSIndexPath *sourceIndexPath;

/* May be useful for computing the UIDragPreviewTarget transform for UICollectionViewDropCoordinator dropItem:toTarget:
 * Returns CGSizeZero if the dragItem does not have a visible drop preview.
 */
@property (nonatomic, readonly) CGSize previewSize;

@end

协议UICollectionViewDropPlaceholderContext

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos)
@protocol UICollectionViewDropPlaceholderContext <UIDragAnimating>

/* Retrieve drop data from the dragItem's itemProvider.
 */
@property (nonatomic, readonly) UIDragItem *dragItem;


/* Exchange the placeholder for the final cell.
 * You are only responsible for updating your data source inside the block using the provided insertionIndexPath.
 * If the placeholder is no longer available (e.g. -reloadData has been called) the dataSourceUpdates block
 * will not be executed and this will return NO.
 */
- (BOOL)commitInsertionWithDataSourceUpdates:(void(NS_NOESCAPE ^)(NSIndexPath *insertionIndexPath))dataSourceUpdates;

/* If the placeholder is no longer needed or you wish to manually insert a cell for the drop data, you can
 * remove the placeholder via this method.
 * If the placeholder is no longer available (e.g. -reloadData has been called) this will return NO.
 */
- (BOOL)deletePlaceholder;

/* Call this method to request an update of the placeholder cell's content via the updateCellHandler.
 * This will only be called if the placeholder is visible. If the placeholder becomes visible via scrolling,
 * the updateCellHandler will automatically be called.
 */
- (void)setNeedsCellUpdate;

@end

枚举 UICollectionViewReorderingCadence

typedef NS_ENUM(NSInteger, UICollectionViewReorderingCadence) {
    UICollectionViewReorderingCadenceImmediate,
    UICollectionViewReorderingCadenceFast,
    UICollectionViewReorderingCadenceSlow
} API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

UICollectionViewDelegate新增方法

// Spring Loading

/* Allows opting-out of spring loading for an particular item.
 *
 * If you want the interaction effect on a different subview of the spring loaded cell, modify the context.targetView property.
 * The default is the cell.
 *
 * If this method is not implemented, the default is YES.
 */
- (BOOL)collectionView:(UICollectionView *)collectionView shouldSpringLoadItemAtIndexPath:(NSIndexPath *)indexPath withContext:(id<UISpringLoadedInteractionContext>)context API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(tvos, watchos);

后记

本篇已结束，后面更精彩~~~