Sample for guideline and percent in ConstraintLayout

constraint_guideline_percent_sample.xml

<?xml version="1.0" encoding="utf-8"?>
<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="wrap_content"
    android:background="#fff">

    <android.support.constraint.Guideline
        android:id="@+id/vertical_center_guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintGuide_percent="0.5"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="タイトル"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toStartOf="@id/vertical_center_guideline"/>

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="YYYY年MM月dd日"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintBottom_toBottomOf="@id/image_view"
        app:layout_constraintEnd_toStartOf="@id/vertical_center_guideline"/>

    <ImageView
        android:id="@+id/image_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="#999"
        app:layout_constraintDimensionRatio="h,8:5"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@id/vertical_center_guideline" />

</android.support.constraint.ConstraintLayout>