如何定位到 ConstraintLayout 中两个视图中最低的位置？

<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">


<TextView
android:id="@+id/header_view_a"
android:layout_width="0dp"
android:layout_height="0dp"
android:background="@android:color/holo_orange_light"
android:gravity="center"
android:text="HeaderViewA "
android:layout_marginBottom="@dimen/sixteenDP"
android:textSize="30sp"
app:layout_constraintBottom_toTopOf="@+id/guideline"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="@+id/header_view_b"
app:layout_constraintEnd_toStartOf="@+id/header_view_b"
app:layout_constraintVertical_bias="0"
app:layout_constraintWidth_default="wrap" />


<TextView
android:id="@+id/header_view_b"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:background="@android:color/holo_green_light"
android:gravity="center"
android:text="HeaderViewB"
android:textAlignment="center"
android:textSize="30sp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toTopOf="@id/guideline"
app:layout_constraintStart_toEndOf="@+id/header_view_a"/>


<android.support.constraint.Guideline
android:id="@+id/guideline"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.4"/>


<TextView
android:id="@+id/big_view"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
android:background="@android:color/holo_blue_dark"
android:gravity="center"
android:text="BigView"
android:textAlignment="center"
android:textSize="@dimen/list_item_height"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="@+id/guideline"
app:layout_constraintVertical_bias="1.0"/>


</android.support.constraint.ConstraintLayout>

Watch out for app:layout_constraintWidth_default="wrap" (with width set to 0dp). If set, the widget will have the same size as if using wrap_content, but will be limited by constraints (i.e. it won't expand beyond them) and app:layout_constraintVertical_bias="1.0". Use bias to pull BigView to the bottom of its parent.

Now it's possible with Barrier class, introduced in constraint-layout v1.1.0.

So here's the solution for your particular case:

<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.eugene.test10.MainActivity">
<TextView
android:id="@+id/textView1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="#EEEEEE"
android:text="TEXT_VIEW_1"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintRight_toLeftOf="@+id/textView2"/>


<TextView
android:id="@+id/textView2"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="#DDDDDD"
android:text="TEXT_VIEW_2"
android:visibility="gone"
app:layout_constraintLeft_toRightOf="@+id/textView1"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />


<android.support.constraint.Barrier
android:id="@+id/labelBarrier"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:barrierDirection="bottom"
app:constraint_referenced_ids="textView1,textView2" />


<TextView
android:id="@+id/textView3"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="#CCCC00"
android:text="TEXT_VIEW_3"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/labelBarrier" />


</android.support.constraint.ConstraintLayout>

Here're results for using this layout:

You can refer this step-by-step guide on Codelab https://codelabs.developers.google.com/codelabs/constraint-layout/#10.