how to set up scrollview for a label in a boxlayout

Question

here is my code

     BoxLayout:
        size_hint: 1, 4
        BoxLayout:
            size_hint: .15, 1
        ScrollView:
            id: sc
            scroll_type:["bars"]
            bar_width: 10
            bar_color: 1,0,0
            BoxLayout:
                size_hint:(1, None)
                height:self.minimum_height
                #size_hint: 1, 1
                Label:
                    #height: sc.height
                    #height:self.height
                    size_hint:(1, None)
                    id: nt
                    color: 1,1,1
                    text:root.textn
                    font_size: "20sp"
                    text_size: self.size
                    valign: "top"
                    halign: "left"
        BoxLayout:
            size_hint: .15, 1

with the above code i get this

it does not show the whole text and the scrollview does not come into effect what can i do?

Answer 1

Here is a modified version of your kv that I think will work for you:

BoxLayout:
    # size_hint: 1, 4   # this would make the BoxLayout 4 times taller than its parent???
    BoxLayout:
        size_hint: .15, 1
    ScrollView:
        id: sc
        size_hint: 1, 0.5
        scroll_type:["bars"]
        bar_width: 10
        bar_color: 1,0,0
        BoxLayout:
            size_hint:(1, None)
            height:self.minimum_height
            Label:
                size_hint:(1, None)
                height: self.texture_size[1]   # this makes the Label fit to height of text
                id: nt
                color: 1,1,1
                text:app.textn
                font_size: "20sp"
                # text_size: self.size   # not needed
                valign: "top"
                halign: "left"
    BoxLayout:
        size_hint: .15, 1

The main point is setting the height of the Label to adjust to its text.