flex-grow-bug-flex.xml

<com.google.android.flexbox.FlexboxLayout 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="wrap_content"
                                          app:flexDirection="row"
                                          android:background="#0c0">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="button1"
            />

        <View android:layout_width="20dp"
              android:layout_height="match_parent"
              />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="button2"
            />

</com.google.android.flexbox.FlexboxLayout>