I need to create two buttons in the bottom of the page with a list view. So I create two stacks in the body of the page and put listview and buttons to them like below:
<z-place inside="Body">
   <Stack Direction="Vertical">
      <Stack Id="top">
  </Stack>
  <Stack Id="bottomMenu" Direction="Horizontal">
    <Button Text="Btn1" CssClass="btmButton1"></Button>
    <Button Text="Btn2" CssClass="btmButton2"></Button>
  </Stack>
 </Stack>
</z-place>
And the stylesheet like this:
//Android.scss
.btmButton1 {
    background: linear-gradient(to bottom, #039795, #196e6d);
    color: #ffffff;
    height: 52px;
    margin: 0;
    border-radius: 0;
}
.btmButton2 {
    background: linear-gradient(to bottom, #5c0eb3, #3f1968);
    color: #ffffff;
    height: 52px;
    margin: 0;
    border-radius: 0;
}
#top {
    height: calc("(Zebble.Device.Screen.Height - view.ActualHeight)-140");
    background: #dadada
}
#bottomMenu {
    width: calc("Zebble.Device.Screen.Width");
    margin-top: calc("(Zebble.Device.Screen.Height - view.ActualHeight)-140");
    position: fixed;
}
But, when I set the #top height buttons was hidden.