PercentLayoutHelper

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

     <android.support.constraint.Guideline
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/left_guideline"
         app:layout_constraintGuide_percent=".15"
         android:orientation="vertical"/&gt

     <android.support.constraint.Guideline
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/right_guideline"
         app:layout_constraintGuide_percent=".85"
         android:orientation="vertical"/&gt

     <android.support.constraint.Guideline
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/top_guideline"
         app:layout_constraintGuide_percent=".15"
         android:orientation="horizontal"/&gt

     <android.support.constraint.Guideline
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/bottom_guideline"
         app:layout_constraintGuide_percent=".85"
         android:orientation="horizontal"/&gt

     <Button
         android:text="Button"
         android:layout_width="0dp"
         android:layout_height="0dp"
         android:id="@+id/button"
         app:layout_constraintLeft_toLeftOf="@+id/left_guideline"
         app:layout_constraintRight_toRightOf="@+id/right_guideline"
         app:layout_constraintTop_toTopOf="@+id/top_guideline"
         app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline" /&gt

 </android.support.constraint.ConstraintLayout&gt

  


  
Helper for layouts that want to support percentage based dimensions.

 
This class collects utility methods that are involved in extracting percentage based dimension
 attributes and applying them to ViewGroup's children. If you would like to implement a layout
 that supports percentage based dimensions, you need to take several steps:

 

 
 You need a ViewGroup.LayoutParams subclass in your ViewGroup that implements
 PercentLayoutHelper.PercentLayoutParams.
 
 In your LayoutParams(Context c, AttributeSet attrs) constructor create an instance
 of PercentLayoutHelper.PercentLayoutInfo by calling
 getPercentLayoutInfo(Context, AttributeSet). Return this
 object from public PercentLayoutHelper.PercentLayoutInfo getPercentLayoutInfo()
 method that you implemented for PercentLayoutHelper.PercentLayoutParams interface.
 
 Override
 setBaseAttributes(TypedArray, int, int)
 with a single line implementation PercentLayoutHelper.fetchWidthAndHeight(this, a,
 widthAttr, heightAttr);
 
 In your ViewGroup override generateLayoutParams(AttributeSet) to return
 your LayoutParams.
 
 In your onMeasure(int, int) override, you need to implement following
 pattern:
 
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     mHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);
     super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     if (mHelper.handleMeasuredStateTooSmall()) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     }
 }