Guideline

public class Guideline
extends View

Utility class representing a Guideline helper object for ConstraintLayout. Helper objects are not displayed on device (they are marked as View.GONE) and are only used for layout purposes. They only work within a ConstraintLayout.

A Guideline can be either horizontal or vertical:

• Vertical Guidelines have a width of zero and the height of their ConstraintLayout parent
• Horizontal Guidelines have a height of zero and the width of their ConstraintLayout parent

Positioning a Guideline is possible in three different ways:

• specifying a fixed distance from the left or the top of a layout (layout_constraintGuide_begin)
• specifying a fixed distance from the right or the bottom of a layout (layout_constraintGuide_end)
• specifying a percentage of the width or the height of a layout (layout_constraintGuide_percent)

Widgets can then be constrained to a Guideline, allowing multiple widgets to be positioned easily from one Guideline, or allowing reactive layout behavior by using percent positioning.

See the list of attributes in ConstraintLayout.LayoutParams to set a Guideline in XML, as well as the corresponding ConstraintSet.setGuidelineBegin(int, int), ConstraintSet.setGuidelineEnd(int, int) and ConstraintSet.setGuidelinePercent(int, float) functions in ConstraintSet.

Example of a Button constrained to a vertical Guideline:

<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.constraint.Guideline
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/guideline"
            app:layout_constraintGuide_begin="100dp"
            android:orientation="vertical"/>

    <Button
            android:text="Button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/button"
            app:layout_constraintLeft_toLeftOf="@+id/guideline"
            android:layout_marginTop="16dp"
            app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

Summary

Public constructors

public Guideline (Context context)

public Guideline (Context context, 
                AttributeSet attrs)

public Guideline (Context context, 
                AttributeSet attrs, 
                int defStyleAttr)

public Guideline (Context context, 
                AttributeSet attrs, 
                int defStyleAttr, 
                int defStyleRes)

Public methods

public void setGuidelineBegin (int margin)

public void setGuidelineEnd (int margin)

public void setGuidelinePercent (float ratio)