Have an ImageView with same width and height in ConstraintLayout

Question

How can we make ImageView width and height equal to width of parent ConstraintLayout? So it displays a full width square ImageView.

Generally how can one set HEIGHT of some widget equal to WIDTH of other?

Answer 1

The following layout will place a square blue image in the center of the parent ConstraintLayout. The key piece is app:layout_constraintDimensionRatio="1:1". Refer to the documentation for details.

You can also define one dimension of a widget as a ratio of the other one. In order to do that, you need to have at least one constrained dimension be set to 0dp (i.e., MATCH_CONSTRAINT), and set the attribute layout_constraintDimensionRatio to a given ratio.

<android.support.constraint.ConstraintLayout 
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@android:color/holo_blue_light"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintDimensionRatio="1:1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>