CollapseAppBar

BindingAdapters.java

public class BindingAdapters {
    @BindingAdapter({"app:setFlags"})
    public static void setFlags(CollapsingToolbarLayout view, int flag) {
        AppBarLayout.LayoutParams params = (AppBarLayout.LayoutParams) view.getLayoutParams();
        params.setScrollFlags(flag);
        view.setLayoutParams(params);
    }
}

CollapsActivityViewModel.kt

...
private void setNormalMode() {
        collapseMode.set(AppBarLayout.LayoutParams.SCROLL_FLAG_SCROLL|AppBarLayout.LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED);
}

fiule.xml

 <android.support.design.widget.CollapsingToolbarLayout
           ...
            app:setFlags="@{viewModel.collapseMode}"
            ...>