android studio constraint layout proportional height
<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="match_parent">
<ImageView
android:id="@+id/img_icon"
android:layout_width="0dp"
android:layout_height="0dp"
android:background="@color/dark_red"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintDimensionRatio="1:1"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintWidth_percent="0.5" />
</android.support.constraint.ConstraintLayout>