How to position below the lowest of two views in ConstraintLayout?

Question

I have two header views, HeaderViewA and HeaderViewB. These views can have any combination of visibility visible or gone.

I need BigView to be positioned under the lowest of either HeaderViewA/HeaderViewB.

Is this possible without nesting in ConstraintLayout?

I'd love to hear a different answer, but afaik this is not possible. — F43nd1r, Feb 21 '17 at 01:31
Interesting, but doesn't look possible just through XML. You don't want nested views, but if you are open to programmatic manipulation you may be able to use [ConstraintSet](https://developer.android.com/reference/android/support/constraint/ConstraintSet.html). — Cheticamp, Feb 21 '17 at 15:17
@AlexMeuer Nested layouts negatively impact on performance (see this report [Understanding the performance benefits of ConstraintLayout](https://android-developers.googleblog.com/2017/08/understanding-performance-benefits-of.html)). So that's the main goal to keep your layout as flat as possible and ConstraintLayout has all the necessary features for it. — Eugene Brusov, Oct 04 '17 at 10:35
@Cheticamp Now, it's possible with using of Barrier class, introduced in constraint-layout v1.1.0. See my answer below... — Eugene Brusov, Oct 05 '17 at 15:49
@EugeneBrusov So I discovered. I believe my comment was before the barrier capability was release. [Here](https://stackoverflow.com/a/44379926/6287910) is a slightly different take on a similar problem. — Cheticamp, Oct 05 '17 at 16:07

score 162 · Accepted Answer · answered Oct 05 '17 at 15:47

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.

Is there anything I need to to first in my project in order to implement Barriers? — Zerato, Nov 15 '17 at 13:57
@Zerato you need to add `'com.android.support.constraint:constraint-layout:1.1.0-beta3'` dependency to your module's gradle file and also add maven repository to project's gradle file. You can find all the dependencies in this GitHub project https://github.com/googlecodelabs/constraint-layout — Eugene Brusov, Nov 15 '17 at 14:56
For those looking to access these barriers via the GUI tool, it's not searchable over with the textview, imageview, etc, but rather in the I-beam looking icon drop down that has guide lines. — MotoRidingMelon, Jul 22 '18 at 19:29

score 2 · Answer 2 · edited Oct 04 '17 at 15:26

<?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.

How to position below the lowest of two views in ConstraintLayout?

2 Answers2