Floating action button in andoidx library

Now you can migrate to Android x and replace the xml with:

<com.google.android.material.floatingactionbutton.FloatingActionButton ... />

Also in the gradle file add:

implementation 'com.google.android.material:material:1.0.0'

To use Floating action button in andoidx library use below dependencies

implementation 'com.google.android.material:material:1.0.0-rc01'

For more information check Migrating to AndroidX

Complete example

XML code

<com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/imgFour"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_close"
        app:backgroundTint="@color/colorAccent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:tint="@android:color/white" />

Notes

app:tint="@android:color/white" is used to change the icon color of FloatingActionButton

app:backgroundTint="@color/colorAccent" is used to change background color of FloatingActionButton

To use FloatingActionButton inside activity or fragment we need to import FloatingActionButton like this

import com.google.android.material.floatingactionbutton.FloatingActionButton