Android :: Split The Screen In 2 Equals Parts With 2 Listviews

I'm trying to put 2 listviews into my layout. The problem is that I don't know the size of each listview in advance. The first listview could have a few items (0, 1, 2 up to roughly 10) and the second listview could have many items (up to 100).

I tried to set the weight of both listviews at 1 but it did not work:

=> If the first listview has only 1 item and the second one 99, you don't see the first item of listview #1 => it's shrinks so much (relative to listview #2) that you don't see it.

So I'm thinking now to split the screen in 2 equals parts (no matter what/no matter the size of each listview) and put the two listviews in each part. Of course it needs to work on any device ... so how do I capture the device screen size, divide it in two and force the listview size to fit in each half of the screen ?

Has anyone done that already ? Is there another option to show two listviews of different sizes on the same layout (should I use a scrollview in some way ? => when the user is reaching the end of the first listview, the second listview appears => is that possible ?)