代码设置ConstraintLayout的layout_constraintDimensionRatio

代码中设置layout_constraintDimensionRatio：

ConstraintSet constraintSet = new ConstraintSet();
constraintSet.clone(mRlContent);
constraintSet.setDimensionRatio(R.id.iv,"h,9:16");
constraintSet.applyTo(mRlContent);

对应布局：

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:contentDescription="@null"
        app:layout_constraintTop_toTopOf="parent"
        tools:background="@drawable/ic_launcher" />

    ...
</androidx.constraintlayout.widget.ConstraintLayout>

参考：
https://www.jianshu.com/p/16e34f919e1a