Touch event on a control under a Transparent Grid

Hi all,

I have a Relative layout like this.

1. Google Map full screen
2. Grid with full screen (BackgroundColor="Transparent"), inside this grid, I have a stacklayout and I set VerticalOptions="End". This also means my control box is always at the bottom of the screen and the google map is behind. Remember my control box height is dynamic. Not fixed

My issue is I want to zoom, drag the google map. But the Grid has a bigger z-index (althought it's Transparent) so I could not touch any event to my google map.

If I set InputTransparent="True" to grid. I can touch the google map but I cannot touch to my control box...

Do you have any suggestion with that kind of layout?

Thank you so much,