app:layout_marginBottom is not working well with android constraint layout

In order to

android:layout_marginBottom="20dp" 

work well, you should use

app:layout_constraintBottom_toBottomOf="parent"

Layout top/bottom margin works only when:

1. constraints in the same direction need to connect with their next neighbor child, like a unidirectional linked list.
2. last constraint in the direction must be set.

In your case, you need to set "layout_constraintBottom_toXXXXX" for each view in the chain, and last view set bottom to parent.

<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="#ade4ad">    <TextView        android:id="@+id/first"        android:layout_width="90dp"        android:layout_height="40dp"        app:layout_marginBottom="10dp"        app:layout_constraintBottom_toTopOf="@+id/second"        android:background="#000"/>    <TextView        android:id="@+id/second"        android:layout_width="90dp"        android:layout_height="40dp"        app:layout_marginBottom="10dp"        app:layout_constraintBottom_toTopOf="@+id/third"        android:background="#fff"/>    <TextView        android:id="@+id/third"        android:layout_width="90dp"        android:layout_height="40dp"        android:background="#fff"        app:layout_constraintBottom_toBottomOf="parent"/></android.support.constraint.ConstraintLayout>

Moreover, reverse dependency is not required except you want "layout_marginTop" works.

you can use that trick, create a space bellow, align to parent bottom

<Space   android:id="@+id/space"   android:layout_width="wrap_content"   android:layout_height="80dp"   app:layout_constraintBottom_toBottomOf="parent"   app:layout_constraintEnd_toEndOf="parent"   app:layout_constraintStart_toStartOf="parent" />

and align your view on top of the space app:layout_constraintBottom_toTopOf="@+id/space"like so

<TextView    android:id="@+id/howNext"    style="@style/white_action_btn_no_border"    android:layout_width="344dp"    android:layout_height="60dp"    android:layout_marginBottom="8dp"    android:layout_marginEnd="8dp"    android:layout_marginStart="8dp"    android:text="@string/got_it_next"    app:layout_constraintBottom_toTopOf="@+id/space"    app:layout_constraintEnd_toEndOf="parent"    app:layout_constraintStart_toStartOf="parent" />