Class

iOSLayoutConstraint

Description

Used to add new auto-layout constraints or modify existing ones.

Methods

Name

Parameters

Returns

Shared

Constructor

firstItem As Object, firstAttribute As iOSLayoutConstraint, relation As iOSLayoutConstraint, secondItem As Object, secondAttribute As iOSLayoutConstraint, multiplier As Double, gap As iOSLayoutConstraint, priority As Double = 1000

Constructor

firstItem As Object, firstAttribute As iOSLayoutConstraint, relation As iOSLayoutConstraint, secondItem As Object, secondAttribute As iOSLayoutConstraint, multiplier As Double, addend As Double, priority As Double = 1000

Enumerations

iOSLayoutConstraint.AttributeTypes

AttributeTypes

Defines the part of the control that will be used for comparison.

Enum

Description

None

No constraint.

Left

The left position of the control.

Right

The right position of the control.

Top

The top position of the control.

Bottom

The bottom position of the control.

Leading

The edge that is the start of text in the current locale (English: left, Hebrew: right).

Trailing

The edge that is the end of text in the current locale (English: right, Hebrew: left).

Width

The width of the control.

Height

The height of the control.

CenterX

Horizontal center

CenterY

Vertical center

Baseline

Bottom of text that does not drop down (like g, p, j, etc). For non-text controls it is the same as the bottom edge.

LeftMargin

The left value padded with the standard margin size.

RightMargin

The right value padded with the standard margin size.

TopMargin

The top value padded with the standard margin size.

BottomMargin

The bottom value padded with the standard margin size.

LeadingMargin

The leading value padded with the standard margin size.

TrailingMargin

The trailing value padded with the standard margin size.

iOSLayoutConstraint.RelationTypes

RelationTypes

The ways in which a property of a control is compared to property of another control.

Enum

Description

LessThanOrEqual

The value must be less than or equal to the value of the related control.

Equal

The value must be equal to the value of the related control.

GreaterThanOrEqual

The value must be greater than or equal to the value of the related control.

Property descriptions

iOSLayoutConstraint.Active

Active As Boolean

Indicates if this auto-layout rule is active.

De-activate an existing named constraint:

' "TAWidth" is a width constraint for a TextField that has been given
' a name in the auto-layout Inspector properties.
Var c As iOSLayoutConstraint = Self.Constraint("TAWidth")
c.Active = False

iOSLayoutConstraint.FirstAttribute

FirstAttribute As AttributeTypes

The attribute of the first control.

This property is read-only.

iOSLayoutConstraint.FirstItem

FirstItem As Object

The control to which the auto-layout rule applies.

This property is read-only.

iOSLayoutConstraint.Offset

Offset As Double

The offset that can be applied to the rule.

Change the offset (in this case the width) or an existing named constraint:

' "TAWidth" is a width constraint for a TextField that has been given
' a name in the auto-layout Inspector properties.
Var c As iOSLayoutConstraint = Self.Constraint("TAWidth")
c.Offset = 200

iOSLayoutConstraint.Priority

Priority As Double

The priority of the rule.

This property is read-only.

Higher priority constraints are met before lower priority constraints.

Priority

Value

Highest

1000

High

800

Medium-High

600

Medium

400

Low

200

iOSLayoutConstraint.Relation

Relation As RelationTypes

The type of relation between the first control and the second control. This is the "Is" item in the Inspector.

This property is read-only.

iOSLayoutConstraint.Scale

Scale As Double

The scale (aka multiplier) for the rule.

This property is read-only.

iOSLayoutConstraint.SecondAttribute

SecondAttribute As AttributeTypes

The attribute to use from the second (related) control. This is the "Edge" item in the Inspector.

This property is read-only.

iOSLayoutConstraint.SecondItem

SecondItem As Object

The related control for the rule. This is the "Relative To" item in the Inspector.

This property is read-only.

iOSLayoutConstraint.StandardGap

StandardGap As Integer

Used to supply a standard gap value when creating a new auto-layout rule. This item can only be used for the gap parameter in the constructor. It has no defined type.

This property is read-only.

This property is shared.

Method descriptions

iOSLayoutConstraint.Constructor

Constructor(firstItem As Object, firstAttribute As iOSLayoutConstraint, relation As iOSLayoutConstraint, secondItem As Object, secondAttribute As iOSLayoutConstraint, multiplier As Double, gap As iOSLayoutConstraint, priority As Double = 1000)

Note

Constructors are special methods called when you create an object with the New keyword and pass in the parameters above.

Creates a new auto-layout rule for the firstItem control with a StandardGap offset value.

iOSLayoutConstraint.Constructor

Constructor(firstItem As Object, firstAttribute As iOSLayoutConstraint, relation As iOSLayoutConstraint, secondItem As Object, secondAttribute As iOSLayoutConstraint, multiplier As Double, addend As Double, priority As Double = 1000)

Note

Constructors are special methods called when you create an object with the New keyword and pass in the parameters above.

Creates a new auto-layout rule for the firstItem control with an addend offset value.

Adds a right constraint to a TextField with an offset of 50 at the highest priority:

' RightConstraintField.Right = Self.Right + 50
Var right As New iOSLayoutConstraint(RightConstraintField, _
  iOSLayoutConstraint.AttributeTypes.Right, _
  iOSLayoutConstraint.RelationTypes.Equal, _
  Self, iOSLayoutConstraint.AttributeTypes.Right, _
  1.0, 50, 1000)

Sample code

This example adds a new button and constraints to the screen.

Var button As New MobileButton
button.Caption = "OK"
Self.AddControl button

' Applying constraints to the screen (Screen1), so they set the position and size of the button when displayed
' (size and position = centered with a margin of 50 points from the parent view edges)

Var RightC As New iOSLayoutConstraint(button,iOSLayoutConstraint.AttributeTypes.Right, iOSLayoutConstraint.RelationTypes.Equal, _
self, iOSLayoutConstraint.AttributeTypes.Right,1.0,-50)

Var LeftC As New iOSLayoutConstraint(button,iOSLayoutConstraint.AttributeTypes.left, iOSLayoutConstraint.RelationTypes.Equal, _
self, iOSLayoutConstraint.AttributeTypes.Left,1.0,50)

Var TopC As New iOSLayoutConstraint(button,iOSLayoutConstraint.AttributeTypes.Top, iOSLayoutConstraint.RelationTypes.Equal, _
self, iOSLayoutConstraint.AttributeTypes.Top,1.0,50)

Var BottomC As New iOSLayoutConstraint(button,iOSLayoutConstraint.AttributeTypes.Bottom, iOSLayoutConstraint.RelationTypes.Equal, _
self, iOSLayoutConstraint.AttributeTypes.bottom,1.0,-50)

Self.AddConstraint RightC
Self.AddConstraint LeftC
Self.AddConstraint TopC
Self.AddConstraint BottomC

Compatibility

iOS projects on the iOS operating system.