Android - Constraint layout - How to align a view centered over edge of other view?

Try this:

<?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"    android:orientation="vertical"    android:padding="20dp">    <android.support.v7.widget.CardView        android:id="@+id/card_1"        android:layout_width="0dp"        android:layout_height="200dp"        android:layout_marginLeft="8dp"        android:layout_marginRight="8dp"        android:layout_marginTop="8dp"        app:layout_constraintLeft_toLeftOf="parent"        app:layout_constraintRight_toRightOf="parent"        app:layout_constraintTop_toTopOf="parent" />    <android.support.v7.widget.CardView        android:id="@+id/card_2"        android:layout_width="100dp"        android:layout_height="100dp"        android:layout_marginBottom="8dp"        android:layout_marginLeft="8dp"        android:layout_marginRight="8dp"        android:layout_marginTop="0dp"        app:cardBackgroundColor="#69F"        app:layout_constraintBottom_toBottomOf="@+id/card_1"        app:layout_constraintLeft_toLeftOf="@+id/card_1"        app:layout_constraintRight_toRightOf="@+id/card_1"        app:layout_constraintTop_toBottomOf="@+id/card_1" /></android.support.constraint.ConstraintLayout>

Explanation :- This works because of these four lines

Following lines sets the blue CardView centered on the bottom edge of White CardView.

<!-- top constraint is set to bottom of White CardView -->app:layout_constraintTop_toBottomOf="@+id/card_1"<!-- bottom constraint is set to bottom of White CardView -->app:layout_constraintBottom_toBottomOf="@+id/card_1"

Following lines set the blue CardView centered horizontally

<!-- left constraint is set to left of White CardView -->app:layout_constraintLeft_toLeftOf="@+id/card_1"<!-- right constraint is set to right of White CardView -->app:layout_constraintRight_toRightOf="@+id/card_1"

try below:

<?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"    android:fitsSystemWindows="true"    app:layout_collapseMode="parallax">    <ImageView        android:id="@+id/imageView_jobBackdrop_jobDetails"        android:layout_width="match_parent"        android:layout_height="175dp"        android:fitsSystemWindows="true"        android:scaleType="centerCrop"        android:background="@android:color/white"        app:layout_collapseMode="parallax"        app:layout_constraintEnd_toEndOf="parent"        app:layout_constraintStart_toStartOf="parent"        app:layout_constraintTop_toTopOf="parent" />    <ImageView        android:id="@+id/imageView2"        android:layout_width="match_parent"        android:layout_height="60dp"        android:layout_marginBottom="8dp"        android:layout_marginEnd="8dp"        android:layout_marginStart="8dp"        android:background="@android:color/black"        app:layout_constraintBottom_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"        app:layout_constraintEnd_toEndOf="@+id/imageView_jobBackdrop_jobDetails"        app:layout_constraintStart_toStartOf="@+id/imageView_jobBackdrop_jobDetails"        app:layout_constraintTop_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"  />    <ImageView        android:id="@+id/imageView3"        android:layout_width="75dp"        android:layout_height="75dp"        android:layout_marginBottom="8dp"        android:layout_marginEnd="8dp"        android:background="@android:color/darker_gray"        app:layout_constraintBottom_toTopOf="@+id/imageView2"        app:layout_constraintEnd_toEndOf="@+id/imageView2"        app:layout_constraintStart_toStartOf="@+id/imageView2"        app:layout_constraintTop_toTopOf="@+id/imageView2"  /></android.support.constraint.ConstraintLayout>