Vertical slider in Xamarin.forms?

问题

I am trying to implement Vertical slider in Xamarin.forms. I know for that I need to create render classes in ios and android respectively. For ios, my renderer seems to be working fine. For android I am following the link https://forums.xamarin.com/discussion/69933/vertical-slider. However the solution provided in above link left me with a slider with no thumb. Is there any way to implement vertical slider for android in Xamarin.forms?

回答1:

This works, sort of. It still has a lot of irritating weirdness to it, but, does the core job of: Has vertical sliders, align next to each other.

<AbsoluteLayout x:Name="slidersAbs" HeightRequest="300" HorizontalOptions="CenterAndExpand" WidthRequest="800">
    <Slider Rotation="-90" Minimum="0" Maximum="50" Value="0"
        AbsoluteLayout.LayoutBounds="0,.5,300,50" AbsoluteLayout.LayoutFlags="PositionProportional"/>
    <Slider Rotation="-90" Minimum="0" Maximum="80" Value="0"
        AbsoluteLayout.LayoutBounds=".5,.5,300,50" AbsoluteLayout.LayoutFlags="PositionProportional"/>
    <Slider Rotation="-90" Minimum="0" Maximum="100" Value="0"
        AbsoluteLayout.LayoutBounds="1,.5,300,50" AbsoluteLayout.LayoutFlags="PositionProportional"/>
</AbsoluteLayout>

Some things I've gleaned from experimentation:

I had to set that WidthRequest to an insanely high number to get the sliders to space out horizontally at all; putting a border on the abs layout might help sort out what's going on there.
You'll notice only the Position (X,Y) is Proportional; if you let the height/width be, it freaks out the way you were running into in other layout approaches, where height and width invert themselves but are still proportional to the screen in the inverse, it's a mess. You just can't use width/height proportional when rotated, at all.
You'd think the insane width and things would cause some kind of scrolling dilemma or other conflict but it actually works perfectly.
I've set the Maximum to 50, 80, 100 so it's easy to tell which is which. As you'd hope, 0 is placed at the bottom of each (not the top - Rotation=90 puts 0 at top, -90 fixes this), and the last slider appears on the right.

https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/slider https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/layouts/absolute-layout

回答2:

I do this way. I think is intuitive and I don't have to worry about coordinates. X and Y are still relative to the wanted actual Left and Top of the Slider. Note the Rectangle bounds in SetLayoutBounds has Height and Width swapped on purpose.

  Slider thisfader = new Slider();
  //coordinates swapped to accomodate rotation
  AbsoluteLayout.SetLayoutBounds(thisfader, new Rectangle(X, Y + Height, Height, Width));
  thisfader.AnchorX = 0; 
  thisfader.AnchorY = 0; //these set the rotation anchor on top left
  thisfader.Rotation = -90;

  AbsoluteLayout.Children.Add(thisfader);