View with elevation and shadow in ConstraintLayout

Question

How can I show elevations in a view with shadows using ConstraintLayout?

With Relative and Linear could perform elevations with shadows to implement list but I can not do it with ConstraintLayout.

<?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="wrap_content"
android:background="#fff"
android:orientation="vertical">

<TextView
    android:id="@+id/list_ssid"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:elevation="8dp"
    android:background="#fff"
    android:text="SSID"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toLeftOf="@+id/guideline"
    app:layout_constraintTop_toTopOf="parent" />
<TextView
    android:id="@+id/list_ch"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginLeft="8dp"
    android:elevation="8dp"
    android:background="#fff"
    android:layout_marginRight="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:text="CH"
    app:layout_constraintLeft_toLeftOf="@+id/guideline"
    app:layout_constraintRight_toLeftOf="@+id/guideline2"
    app:layout_constraintTop_toTopOf="parent" />
<TextView
    android:id="@+id/list_dB"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginLeft="8dp"
    android:elevation="8dp"
    android:background="#fff"
    android:layout_marginRight="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:text="dB"
    app:layout_constraintLeft_toLeftOf="@+id/guideline2"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
<android.support.constraint.Guideline
    android:id="@+id/guideline"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.65"
    tools:layout_editor_absoluteX="239dp"
    tools:layout_editor_absoluteY="0dp" />
  <android.support.constraint.Guideline
    android:id="@+id/guideline2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.83"
    tools:layout_editor_absoluteX="306dp"
    tools:layout_editor_absoluteY="0dp" />
   </android.support.constraint.ConstraintLayout>

Answer 1

In order to make elevation work, you need to just set a background color to a view.

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@color/your_color"
    android:text="SSID"/>

Doesn't matter what kind of View it is,
a child of ConstraintLayout or ConstraintLayout itself

You also may use hex color or color attribute.
Just note that it mustn't be fully transparent.

Answer 2

For some reason, elevation works in ConstraintLayout if you give a dummy drawable as the background::

Create a drawable:

dummyBg.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@android:color/white"/>
            <corners android:radius="2dp" />
        </shape>
    </item>
</layer-list>

Use this as the background for the view and use elevation as you normally would.

    android:elevation="8dp"
    android:background="@drawable/dummyBg"
    android:padding="4dp"

So you'd get:

<TextView
    android:id="@+id/list_ssid"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="6dp"
    android:layout_marginBottom="2dp"
    android:elevation="8dp"
    android:background="@drawable/dummyBg"
    android:padding="4dp"
    android:text="SSID"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toLeftOf="@+id/guideline"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintBottom_toBottomOf="parent"/>