ConstraintLayout ratios allow one dimension of a widget to be sized relative to the widget’s other dimension (otherwise known as aspect ratio). An aspect ratio setting could, for example, be applied to an ImageView to ensure that its width is always twice its height.
A dimension ratio constraint is configured by setting the constrained dimension to match constraint mode and configuring the layout_constraintDimensionRatio attribute on that widget to the required ratio. This ratio value may be specified either as a float value or a width:height ratio setting. The following XML excerpt, for example, configures a ratio of 2:1 on an ImageView widget:
<ImageView
android:layout_width="0dp"
android:layout_height="100dp"
android:id="@+id/imageView"
...
