NSLayoutConstraint Class

Reference

Definition

Namespace:: UIKit

Assembly:: Xamarin.iOS.dll

Important

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A relationship between two layout attributes used in a constraint-based layout.

[Foundation.Register("NSLayoutConstraint", true)]
[ObjCRuntime.Introduced(ObjCRuntime.PlatformName.iOS, 6, 0, ObjCRuntime.PlatformArchitecture.All, null)]
[ObjCRuntime.Unavailable(ObjCRuntime.PlatformName.WatchOS, ObjCRuntime.PlatformArchitecture.All, null)]
public class NSLayoutConstraint : Foundation.NSObject

type NSLayoutConstraint = class
    inherit NSObject

Inheritance: Object

NSObject
NSLayoutConstraint

Attributes: RegisterAttribute IntroducedAttribute UnavailableAttribute

Remarks

An NSLayoutConstraint specifies the relationship between two layout attributes (FirstAttribute and SecondAttribute, both of which are of type NSLayoutAttribute) in a constraint-based layout.

The relationship consists of:

A NSLayoutRelation (e.g., GreaterThanOrEqual):
A floating point Multiplier:
A single-precision floating point Constant:
A floating point Priority. Constraints with higher priorities are satisfied before constraints with lower priorities.:

The constraint engine will set the value of the FirstAttribute such that it satisfies the constraint FirstAttribute <Relation> <Constant> + <Multiplier> * <SecondAttribute>. For instance, in the following code from the "Media Notes" sample, tconstraint2 is a constraint that specifies that the top of the toolbar is going to be equal to the top of the View plus the value of the toolbarVerticalOffset, while tconstraint1 specifies that the width of the toolbar will be equal to the width of the View. Both of these constraints have a Priority of 1.0.

var tconstraint2 = NSLayoutConstraint.Create (toolbar, NSLayoutAttribute.Top, NSLayoutRelation.Equal,
                                                View, NSLayoutAttribute.Top, 1.0f, toolbarVerticalOffset);
toolbarTopConstraint = tconstraint2;
var tconstraint1 = NSLayoutConstraint.Create (toolbar, NSLayoutAttribute.Width, NSLayoutRelation.Equal,
                                                View, NSLayoutAttribute.Width, 1.0f, 0.0f);

Constructors

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

Properties

Active	Controls whether the constraint is active. Active constraints are used as part of the auto-layout process, those that are not are ignored.
Class	(Inherited from NSObject)
ClassHandle	The handle for this class.
Constant	Indicates the constant float applied to the constraint.
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)
FirstAttribute	The attribute of the first item participating in the constraint.
FirstItem	The first item participating in the constraint.
Handle	Handle (pointer) to the unmanaged object representation. (Inherited from NSObject)
IsDirectBinding	(Inherited from NSObject)
IsProxy	(Inherited from NSObject)
Multiplier	Applied to the second attribute participating in the constraint.
Priority	The priority of the constraint. Must be in range [0, UILayoutPriority.Required].
Relation	The NSRelation that holds between the two items in the constraint.
RetainCount	Returns the current Objective-C retain count for the object. (Inherited from NSObject)
SecondAttribute	The attribute of the second item participating in the constraint.
SecondItem	The second item participating in the constraint.
Self	(Inherited from NSObject)
ShouldBeArchived	Whether the constraint should be archived by its owning UIView.
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

ActivateConstraints(NSLayoutConstraint[])	Activates all of the constraints passed.
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)
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)
Create(INativeObject, NSLayoutAttribute, NSLayoutRelation, INativeObject, NSLayoutAttribute, nfloat, nfloat)	Factory method for creating a constraint.
Create(NSObject, NSLayoutAttribute, NSLayoutRelation, nfloat, nfloat)	Static factory method for creating a constraint.
Create(NSObject, NSLayoutAttribute, NSLayoutRelation, NSObject, NSLayoutAttribute, nfloat, nfloat)	Factory method for creating a constraint.
Create(NSObject, NSLayoutAttribute, NSLayoutRelation)	Static factory method to create a constraint based on a UIView, an T:NSLayoutAttribute, and an NSLayoutRelation.
DangerousAutorelease()	(Inherited from NSObject)
DangerousRelease()	(Inherited from NSObject)
DangerousRetain()	(Inherited from NSObject)
DeactivateConstraints(NSLayoutConstraint[])	Deactivates all of the constraints passed.
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)
DidChangeValue(String)	Indicates that a change occurred on the specified key. (Inherited from NSObject)
Dispose()	Releases the resources used by the NSObject object. (Inherited from NSObject)
Dispose(Boolean)	Releases the resources used by the NSLayoutConstraint object.
DoesNotRecognizeSelector(Selector)	Indicates that this object does not recognize the specified selector. (Inherited from NSObject)
Equals(NSObject)	(Inherited from NSObject)
Equals(Object)	(Inherited from NSObject)
ExposedBindings()	(Inherited from NSObject)
FirstAnchor<AnchorType>()	For an anchor-based constraint, returns the first anchor, properly downcast to `AnchorType`.
FromVisualFormat(String, NSLayoutFormatOptions, NSDictionary, NSDictionary)	Factory method for creating a constraint using Visual Format Language.
FromVisualFormat(String, NSLayoutFormatOptions, Object[])	Factory method for creating a constraint using Visual Format Language.
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)
GetMethodForSelector(Selector)	(Inherited from NSObject)
GetNativeField(String)	Obsolete. (Inherited from NSObject)
GetNativeHash()	(Inherited from NSObject)
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)
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)
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)
SecondAnchor<AnchorType>()	For an anchor-based constraint, returns the second anchor, properly downcast to `AnchorType`.
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)
ToString()	Returns a string representation of the value of the current instance. (Inherited from NSObject)
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)
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)

Extension Methods

GetDebugDescription(INSObjectProtocol)
GetIdentifier(NSLayoutConstraint)
Identifier(NSLayoutConstraint)	Obsolete. Returns an identifier that can be used to request an item.
SetIdentifier(NSLayoutConstraint, String)
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.

Applies to

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