UICollectionViewDelegate Class

Reference

Definition

Namespace:: UIKit

Assembly:: Xamarin.iOS.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Used to receive notices relating to a UICollectionView.

[Foundation.Protocol]
[Foundation.Register("UICollectionViewDelegate", false)]
[ObjCRuntime.Introduced(ObjCRuntime.PlatformName.iOS, 6, 0, ObjCRuntime.PlatformArchitecture.All, null)]
public class UICollectionViewDelegate : Foundation.NSObject, IDisposable, UIKit.IUICollectionViewDelegate

type UICollectionViewDelegate = class
    inherit NSObject
    interface IUICollectionViewDelegate
    interface INativeObject
    interface IDisposable
    interface IUIScrollViewDelegate

Inheritance: Object

NSObject
UICollectionViewDelegate

Derived: UIKit.UICollectionViewDelegateFlowLayout

Attributes: ProtocolAttribute RegisterAttribute IntroducedAttribute

Implements: INativeObject IDisposable IUICollectionViewDelegate IUIScrollViewDelegate

Remarks

Methods within UICollectionViewDelegate are called in reaction to events occurring within an associated UICollectionView. To use this class, you must derive from it and override its method to respond to events.

Although UICollectionView is a subtype of UIScrollView, UICollectionViewDelegate is not a subtype of UIScrollViewDelegate. Nonetheless, many of the methods in UICollectionViewDelegate mirror those of UIScrollViewDelegate and application developers may find it useful to consult the documentation of that class for a more detailed discussion of methods relating to scrolling.

The UICollectionViewSource class provides an alternative to this class, combining the UICollectionViewDelegate API and the UICollectionViewDataSource APIs. It is available via the Source property.

Selecting and Highlighting

Selecting and highlighting in a UICollectionView follows this sequence:

User Action	UICollectionViewDelegate Methods	UICollectionViewCell Properties
Nothing touched		`Highlighted == false; Selected == false`
Finger down in cell	ShouldHighlightItem(UICollectionView, NSIndexPath) is called. If it returns `false`, processing stops.
	ItemHighlighted(UICollectionView, NSIndexPath) is called.	`Highlighted == true; Selected == false`
Finger up	ShouldSelectItem(UICollectionView, NSIndexPath) is called. If it returns `false`, processing stops.
	ItemSelected(UICollectionView, NSIndexPath) is called. ItemUnhighlighted(UICollectionView, NSIndexPath) is called.	`Highlighted == false; Selected == true`

Deselecting a UICollectionViewCell follows a similar sequence:

User Action UICollectionViewDelegate Methods UICollectionViewCell Properties

User Action	UICollectionViewDelegate Methods	UICollectionViewCell Properties
Nothing touched while some UICollectionViewCell is highlighted.		`Highlighted == false; Selected == true`
Finger taps cell (Deselect gesture)	ShouldDeselectItem(UICollectionView, NSIndexPath) is called. If it returns `false`, processing stops.
	ItemDeselected(UICollectionView, NSIndexPath) is called.	`Highlighted == false; Selected == false`

Nothing touched while some UICollectionViewCell is highlighted.

Highlighted == false; Selected == true

Finger taps cell (Deselect gesture) ShouldDeselectItem(UICollectionView, NSIndexPath) is called. If it returns false, processing stops.

ItemDeselected(UICollectionView, NSIndexPath) is called.

Highlighted == false; Selected == false

Constructors

UICollectionViewDelegate()	Default constructor, initializes a new instance of this class.
UICollectionViewDelegate(IntPtr)	A constructor used when creating managed representations of unmanaged objects; Called by the runtime.
UICollectionViewDelegate(NSObjectFlag)	Constructor to call on derived classes to skip initialization and merely allocate the object.

Properties

Class	(Inherited from NSObject)
ClassHandle	The handle for this class. (Inherited from NSObject)
DebugDescription	A developer-meaningful description of this object. (Inherited from NSObject)
Description	Description of the object, the Objective-C version of ToString. (Inherited from NSObject)
Handle	Handle (pointer) to the unmanaged object representation. (Inherited from NSObject)
IsDirectBinding	(Inherited from NSObject)
IsProxy	(Inherited from NSObject)
RetainCount	Returns the current Objective-C retain count for the object. (Inherited from NSObject)
Self	(Inherited from NSObject)
Superclass	(Inherited from NSObject)
SuperHandle	Handle used to represent the methods in the base class for this NSObject. (Inherited from NSObject)
Zone	(Inherited from NSObject)

Methods

AddObserver(NSObject, NSString, NSKeyValueObservingOptions, IntPtr)	Registers an object for being observed externally (using NSString keyPath). Observed changes are dispatched to the observer’s object ObserveValue(NSString, NSObject, NSDictionary, IntPtr) method. (Inherited from NSObject)
AddObserver(NSObject, String, NSKeyValueObservingOptions, IntPtr)	Registers an object for being observed externally (using string keyPath). Observed changes are dispatched to the observer’s object ObserveValue(NSString, NSObject, NSDictionary, IntPtr) method. (Inherited from NSObject)
AddObserver(NSString, NSKeyValueObservingOptions, Action<NSObservedChange>)	Registers an object for being observed externally using an arbitrary method. (Inherited from NSObject)
AddObserver(String, NSKeyValueObservingOptions, Action<NSObservedChange>)	Registers an object for being observed externally using an arbitrary method. (Inherited from NSObject)
AwakeFromNib()	Called after the object has been loaded from the nib file. Overriders must call base.AwakeFromNib(). (Inherited from NSObject)
BeginInvokeOnMainThread(Action)	(Inherited from NSObject)
BeginInvokeOnMainThread(Selector, NSObject)	Invokes asynchrously the specified code on the main UI thread. (Inherited from NSObject)
Bind(NSString, NSObject, String, NSDictionary)	(Inherited from NSObject)
Bind(String, NSObject, String, NSDictionary)	Obsolete. (Inherited from NSObject)
BindingInfo(String)	Obsolete. (Inherited from NSObject)
BindingOptionDescriptions(String)	Obsolete. (Inherited from NSObject)
BindingValueClass(String)	Obsolete. (Inherited from NSObject)
CanFocusItem(UICollectionView, NSIndexPath)	Whether the item at `indexPath` can be focused.
CanPerformAction(UICollectionView, Selector, NSIndexPath, NSObject)	Whether this UICollectionViewDelegate can perform the specified action on an item in the UICollectionView.
CellDisplayingEnded(UICollectionView, UICollectionViewCell, NSIndexPath)	Indicates that the specified cell was removed from the UICollectionView.
CommitEditing()	(Inherited from NSObject)
CommitEditing(NSObject, Selector, IntPtr)	(Inherited from NSObject)
ConformsToProtocol(IntPtr)	Invoked to determine if this object implements the specified protocol. (Inherited from NSObject)
Copy()	Performs a copy of the underlying Objective-C object. (Inherited from NSObject)
DangerousAutorelease()	(Inherited from NSObject)
DangerousRelease()	(Inherited from NSObject)
DangerousRetain()	(Inherited from NSObject)
DecelerationEnded(UIScrollView)	Indicates that deceleration from a scrolling event has completed.
DecelerationStarted(UIScrollView)	Indicates that deceleration from a scrolling event has begun.
DidChange(NSKeyValueChange, NSIndexSet, NSString)	Indicates a change occurred to the indexes for a to-many relationship. (Inherited from NSObject)
DidChange(NSString, NSKeyValueSetMutationKind, NSSet)	(Inherited from NSObject)
DidChangeAdjustedContentInset(UIScrollView)	Method that is called when the inset values change.
DidChangeValue(String)	Indicates that a change occurred on the specified key. (Inherited from NSObject)
DidUpdateFocus(UICollectionView, UICollectionViewFocusUpdateContext, UIFocusAnimationCoordinator)	Delegate method called shortly after focus has changed to a new UIView.
DidZoom(UIScrollView)	Indicates that zooming has occurred.
Dispose()	Releases the resources used by the NSObject object. (Inherited from NSObject)
Dispose(Boolean)	Releases the resources used by the NSObject object. (Inherited from NSObject)
DoesNotRecognizeSelector(Selector)	Indicates that this object does not recognize the specified selector. (Inherited from NSObject)
DraggingEnded(UIScrollView, Boolean)	Indicates that dragging has completed.
DraggingStarted(UIScrollView)	Indicates that dragging has begun.
Equals(NSObject)	(Inherited from NSObject)
Equals(Object)	(Inherited from NSObject)
ExposedBindings()	(Inherited from NSObject)
GetBindingInfo(NSString)	(Inherited from NSObject)
GetBindingOptionDescriptions(NSString)	(Inherited from NSObject)
GetBindingValueClass(NSString)	(Inherited from NSObject)
GetDictionaryOfValuesFromKeys(NSString[])	Retrieves the values of the specified keys. (Inherited from NSObject)
GetHashCode()	Generates a hash code for the current instance. (Inherited from NSObject)
GetIndexPathForPreferredFocusedView(UICollectionView)	When overridden, allows the developer to specify the item that should initially receive focus.
GetMethodForSelector(Selector)	(Inherited from NSObject)
GetNativeField(String)	Obsolete. (Inherited from NSObject)
GetNativeHash()	(Inherited from NSObject)
GetTargetContentOffset(UICollectionView, CGPoint)	When overridden, allows the developer to modify the content offset for layout and animation changes.
GetTargetIndexPathForMove(UICollectionView, NSIndexPath, NSIndexPath)	When overridden, allows the developer to modify the final location of a moved item. (For instance, to disallow a move to a particular `proposedIndexPath`.)
Init()	(Inherited from NSObject)
InitializeHandle(IntPtr, String)	(Inherited from NSObject)
InitializeHandle(IntPtr)	(Inherited from NSObject)
Invoke(Action, Double)	(Inherited from NSObject)
Invoke(Action, TimeSpan)	(Inherited from NSObject)
InvokeOnMainThread(Action)	(Inherited from NSObject)
InvokeOnMainThread(Selector, NSObject)	Invokes synchrously the specified code on the main UI thread. (Inherited from NSObject)
IsEqual(NSObject)	(Inherited from NSObject)
IsKindOfClass(Class)	(Inherited from NSObject)
IsMemberOfClass(Class)	(Inherited from NSObject)
ItemDeselected(UICollectionView, NSIndexPath)	Indicates that the item at the specified index was deselected.
ItemHighlighted(UICollectionView, NSIndexPath)	Indicates that the specified item was highlighted.
ItemSelected(UICollectionView, NSIndexPath)	Indicates that the item at the specified index was selected.
ItemUnhighlighted(UICollectionView, NSIndexPath)	Indicates that the item at the specified index had its highlight removed.
MarkDirty()	Promotes a regular peer object (IsDirectBinding is true) into a toggleref object. (Inherited from NSObject)
MutableCopy()	Creates a mutable copy of the specified NSObject. (Inherited from NSObject)
ObjectDidEndEditing(NSObject)	(Inherited from NSObject)
ObserveValue(NSString, NSObject, NSDictionary, IntPtr)	Indicates that the value at the specified keyPath relative to this object has changed. (Inherited from NSObject)
PerformAction(UICollectionView, Selector, NSIndexPath, NSObject)	Performs the specified action on an item in the UICollectionView.
PerformSelector(Selector, NSObject, Double, NSString[])	(Inherited from NSObject)
PerformSelector(Selector, NSObject, Double)	Invokes the selector on the current instance and if the `obj` is not null, it passes this as its single parameter. (Inherited from NSObject)
PerformSelector(Selector, NSObject, NSObject)	(Inherited from NSObject)
PerformSelector(Selector, NSObject)	(Inherited from NSObject)
PerformSelector(Selector, NSThread, NSObject, Boolean, NSString[])	(Inherited from NSObject)
PerformSelector(Selector, NSThread, NSObject, Boolean)	(Inherited from NSObject)
PerformSelector(Selector)	(Inherited from NSObject)
PrepareForInterfaceBuilder()	(Inherited from NSObject)
RemoveObserver(NSObject, NSString, IntPtr)	Stops the specified observer from receiving further notifications of changed values for the specified keyPath and context. (Inherited from NSObject)
RemoveObserver(NSObject, NSString)	Stops the specified observer from receiving further notifications of changed values for the specified keyPath. (Inherited from NSObject)
RemoveObserver(NSObject, String, IntPtr)	Stops the specified observer from receiving further notifications of changed values for the specified keyPath and context. (Inherited from NSObject)
RemoveObserver(NSObject, String)	Stops the specified observer from receiving further notifications of changed values for the specified keyPath. (Inherited from NSObject)
RespondsToSelector(Selector)	Whether this object recognizes the specified selector. (Inherited from NSObject)
ScrollAnimationEnded(UIScrollView)	Indicates that animation relating to a scrolling event has completed.
Scrolled(UIScrollView)	Indicates that scrolling occurred.
ScrolledToTop(UIScrollView)	Indicates that the UICollectionView has scrolled to its beginning.
SetNativeField(String, NSObject)	Obsolete. (Inherited from NSObject)
SetNilValueForKey(NSString)	Sets the value of the specified key to null. (Inherited from NSObject)
SetValueForKey(NSObject, NSString)	Sets the value of the property specified by the key to the specified value. (Inherited from NSObject)
SetValueForKeyPath(IntPtr, NSString)	A constructor used when creating managed representations of unmanaged objects; Called by the runtime. (Inherited from NSObject)
SetValueForKeyPath(NSObject, NSString)	Sets the value of a property that can be reached using a keypath. (Inherited from NSObject)
SetValueForUndefinedKey(NSObject, NSString)	Indicates an attempt to write a value to an undefined key. If not overridden, raises an NSUndefinedKeyException. (Inherited from NSObject)
SetValuesForKeysWithDictionary(NSDictionary)	Sets the values of this NSObject to those in the specified dictionary. (Inherited from NSObject)
ShouldDeselectItem(UICollectionView, NSIndexPath)	Whether the specified item should be deselected.
ShouldHighlightItem(UICollectionView, NSIndexPath)	Whether the specified item should be highlighted during tracking.
ShouldScrollToTop(UIScrollView)	Whether the UICollectionView should scroll to its beginning.
ShouldSelectItem(UICollectionView, NSIndexPath)	Whether the specified item should be selected.
ShouldShowMenu(UICollectionView, NSIndexPath)	Whether an action menu should be displayed for the specified item.
ShouldSpringLoadItem(UICollectionView, NSIndexPath, IUISpringLoadedInteractionContext)	Method that is called to indicate whether the identified item should springload in the specified context.
ShouldUpdateFocus(UICollectionView, UICollectionViewFocusUpdateContext)	Called prior to a cell in the `collectionView` either losing or receiving focus. If either focus environment returns `false`, the focus update is canceled.
SupplementaryViewDisplayingEnded(UICollectionView, UICollectionReusableView, NSString, NSIndexPath)	Indicates that the specified supplementary view was removed from the UICollectionView.
ToString()	Returns a string representation of the value of the current instance. (Inherited from NSObject)
TransitionLayout(UICollectionView, UICollectionViewLayout, UICollectionViewLayout)	A custom transition layout for use when moving between selected layouts.
Unbind(NSString)	(Inherited from NSObject)
Unbind(String)	Obsolete. (Inherited from NSObject)
ValueForKey(NSString)	Returns the value of the property associated with the specified key. (Inherited from NSObject)
ValueForKeyPath(NSString)	Returns the value of a property that can be reached using a keypath. (Inherited from NSObject)
ValueForUndefinedKey(NSString)	Indicates an attempt to read a value of an undefined key. If not overridden, raises an NSUndefinedKeyException. (Inherited from NSObject)
ViewForZoomingInScrollView(UIScrollView)	The UIView to use when zooming is about to occur.
WillChange(NSKeyValueChange, NSIndexSet, NSString)	Indicates that the values of the specified indices in the specified key are about to change. (Inherited from NSObject)
WillChange(NSString, NSKeyValueSetMutationKind, NSSet)	(Inherited from NSObject)
WillChangeValue(String)	Indicates that the value of the specified key is about to change. (Inherited from NSObject)
WillDisplayCell(UICollectionView, UICollectionViewCell, NSIndexPath)	The `cell` is about to be displayed.
WillDisplaySupplementaryView(UICollectionView, UICollectionReusableView, String, NSIndexPath)	The supplementary `view` is about to be displayed.
WillEndDragging(UIScrollView, CGPoint, CGPoint)	Indicates that dragging is about to complete.
ZoomingEnded(UIScrollView, UIView, nfloat)	Indicates that zooming has completed.
ZoomingStarted(UIScrollView, UIView)	Indicates that zooming has begun.

Extension Methods

GetDebugDescription(INSObjectProtocol)
GetAccessibilityCustomRotors(NSObject)	Gets the array of UIAccessibilityCustomRotor objects appropriate for `this` object.
SetAccessibilityCustomRotors(NSObject, UIAccessibilityCustomRotor[])	Sets the array of UIAccessibilityCustomRotor objects appropriate for `this` object.
CanFocusItem(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Whether the item at `indexPath` can be focused.
CanPerformAction(IUICollectionViewDelegate, UICollectionView, Selector, NSIndexPath, NSObject)	Whether the cell at the specified `indexPath` supports the specified action.
CellDisplayingEnded(IUICollectionViewDelegate, UICollectionView, UICollectionViewCell, NSIndexPath)	Indicates that the cell at the specified indexPath has been removed.
DidUpdateFocus(IUICollectionViewDelegate, UICollectionView, UICollectionViewFocusUpdateContext, UIFocusAnimationCoordinator)	Indicates that the focus changed as detailed in the `context`.
GetIndexPathForPreferredFocusedView(IUICollectionViewDelegate, UICollectionView)	When overridden, allows the developer to specify the item that should initially receive focus.
GetTargetContentOffset(IUICollectionViewDelegate, UICollectionView, CGPoint)	When overridden, allows the developer to modify the content offset for layout and animation changes.
GetTargetIndexPathForMove(IUICollectionViewDelegate, UICollectionView, NSIndexPath, NSIndexPath)	When overridden, allows the developer to modify the final location of a moved item. (For instance, to disallow a move to a particular `proposedIndexPath`.)
ItemDeselected(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Indicates that the cell at the specified indexPath has been deselected.
ItemHighlighted(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Indicates that the cell at the specified indexPath has been highlighted.
ItemSelected(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Indicates that the cell at the specified indexPath has been selected.
ItemUnhighlighted(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Indicates that the cell at the specified indexPath has been unhighlighted.
PerformAction(IUICollectionViewDelegate, UICollectionView, Selector, NSIndexPath, NSObject)	Whether the cell at the specified indexPath supports the specified Copy or Paste action.
ShouldDeselectItem(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Whether the cell at the specified indexPath should allow itself to be deselected.
ShouldHighlightItem(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Whether the cell at the specified indexPath should allow itself to be highlighted.
ShouldSelectItem(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Whether the cell at the specified indexPath allows itself to be selected.
ShouldShowMenu(IUICollectionViewDelegate, UICollectionView, NSIndexPath)	Whether the cell at the specified indexPath should show an Action menu.
ShouldSpringLoadItem(IUICollectionViewDelegate, UICollectionView, NSIndexPath, IUISpringLoadedInteractionContext)	Method that is called to indicate whether the identified item should springload in the specified context.
ShouldUpdateFocus(IUICollectionViewDelegate, UICollectionView, UICollectionViewFocusUpdateContext)	When overridden, allows the developer to prevent the focus change specified in `context`.
SupplementaryViewDisplayingEnded(IUICollectionViewDelegate, UICollectionView, UICollectionReusableView, NSString, NSIndexPath)	Indicates that the supplementary view at the specified indexPath has been removed.
TransitionLayout(IUICollectionViewDelegate, UICollectionView, UICollectionViewLayout, UICollectionViewLayout)	The UICollectionViewTransitionLayout to be used when moving from the specified fromLayout to the toLayout.
WillDisplayCell(IUICollectionViewDelegate, UICollectionView, UICollectionViewCell, NSIndexPath)	The `cell` is about to be displayed.
WillDisplaySupplementaryView(IUICollectionViewDelegate, UICollectionView, UICollectionReusableView, String, NSIndexPath)	The supplementary `view` is about to be displayed.
DecelerationEnded(IUIScrollViewDelegate, UIScrollView)	Indicates that deceleration relating to a scroll event has ended.
DecelerationStarted(IUIScrollViewDelegate, UIScrollView)	Indicates that deceleration of a scrolling event has begun.
DidChangeAdjustedContentInset(IUIScrollViewDelegate, UIScrollView)	Method that is called when the inset values change.
DidZoom(IUIScrollViewDelegate, UIScrollView)	Indicates that the specified scrollView has zoomed.
DraggingEnded(IUIScrollViewDelegate, UIScrollView, Boolean)	Indicates that dragging has completed.
DraggingStarted(IUIScrollViewDelegate, UIScrollView)	Indicates that dragging has begun.
ScrollAnimationEnded(IUIScrollViewDelegate, UIScrollView)	Indicates that all animations relating to scrolling have completed.
Scrolled(IUIScrollViewDelegate, UIScrollView)	Indicates that the specified scrollView has scrolled.
ScrolledToTop(IUIScrollViewDelegate, UIScrollView)	Indicates that the specified scrollView's scrolling has ended at the top.
ShouldScrollToTop(IUIScrollViewDelegate, UIScrollView)	Whether a scroll to the beginning of the scrollView should be permitted.
ViewForZoomingInScrollView(IUIScrollViewDelegate, UIScrollView)	The UIView to scale when zooming is requested.
WillEndDragging(IUIScrollViewDelegate, UIScrollView, CGPoint, CGPoint)	Indicates that dragging is about to end.
ZoomingEnded(IUIScrollViewDelegate, UIScrollView, UIView, nfloat)	Indicates that zooming has completed.
ZoomingStarted(IUIScrollViewDelegate, UIScrollView, UIView)	Indicates that zooming has begun.

Applies to

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