# androidx.constraintlayout.widget # androidx.constraintlayout.widget *** ** * ** *** Kotlin\|[Java](https://developer.android.com/reference/androidx/constraintlayout/widget/package-summary "View this page in Java") ## Interfaces |--------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------| | [ConstraintLayout.ValueModifier](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout.ValueModifier) | This is the interface to a valued modifier. implement this and add it using addValueModifier | | [SharedValues.SharedValuesListener](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/SharedValues.SharedValuesListener) | interface for listeners | ## Classes |------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | [Barrier](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Barrier) | **Added in 1.1** | | [ConstraintAttribute](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintAttribute) | Defines non standard Attributes | | [ConstraintHelper](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintHelper) | **Added in 1.1** | | [ConstraintLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout) | A`ConstraintLayout`is a[android.view.ViewGroup](https://developer.android.com/reference/android/view/ViewGroup.html)which allows you to position and size widgets in a flexible way. | | [ConstraintLayout.LayoutParams](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout.LayoutParams) | This class contains the different attributes specifying how a view want to be laid out inside a[ConstraintLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout). | | [ConstraintLayoutStates](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayoutStates) | | | [ConstraintLayoutStatistics](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayoutStatistics) | This provide metrics of the complexity of the layout that is being solved. | | [ConstraintProperties](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintProperties) | **Added in 2.0** | | [ConstraintSet](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet) | Defines a set of constraints to be used with[ConstraintLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout). | | [ConstraintSet.Constraint](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet.Constraint) | | | [ConstraintSet.Layout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet.Layout) | | | [ConstraintSet.Motion](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet.Motion) | | | [ConstraintSet.PropertySet](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet.PropertySet) | | | [ConstraintSet.Transform](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintSet.Transform) | | | [Constraints](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Constraints) | This defines the internally defined Constraint set It allows you to have a group of References which point to other views and provide them with constraint attributes | | [Constraints.LayoutParams](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Constraints.LayoutParams) | | | [ConstraintsChangedListener](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintsChangedListener) | **Added in 2.0** | | [Group](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Group) | Control the visibility and elevation of the referenced views**Added in 1.1** | | [Guideline](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Guideline) | Utility class representing a Guideline helper object for[ConstraintLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout). | | [Placeholder](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/Placeholder) | **Added in 1.1** | | [ReactiveGuide](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ReactiveGuide) | Utility class representing a reactive Guideline helper object for[ConstraintLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintLayout). | | [SharedValues](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/SharedValues) | Shared values | | [StateSet](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/StateSet) | | | [VirtualLayout](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/VirtualLayout) | **Added in 2.0** | ## Enums |--------------------------------------------------------------------------------------------------------------------------------------------------------|---| | [ConstraintAttribute.AttributeType](https://developer.android.com/reference/kotlin/androidx/constraintlayout/widget/ConstraintAttribute.AttributeType) | |