无法更改列表视图xamarin.forms中的字体大小

Question

Why can't change font size in listview

i want increase and decrease font size in all cells in listview but i can't make that by normal code

txt.Fontsize = 20;

this my code in xaml

 <ListView  AbsoluteLayout.LayoutBounds="0,0,1,0.865" AbsoluteLayout.LayoutFlags="All" x:Name="listview" BackgroundColor="White" HasUnevenRows="true" ItemsSource="{Binding names}" ><ListView.ItemTemplate>

       <DataTemplate>

                <ViewCell>

                    <StackLayout  Padding="10"  VerticalOptions="Center" >
        <Label  x:Name="txt" HorizontalTextAlignment="End" TextColor="Black" Text="{Binding _index}  "></Label> 

                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

Answer 1

i found solution by slider value

<Slider Maximum="50" Minimum="20"  x:Name="slider" AbsoluteLayout.LayoutBounds="0.5,0.1,0.6,0.02" AbsoluteLayout.LayoutFlags="All" ></Slider>

and in lable :-

    <Label  x:Name="txt" FontSize="{Binding Source={x:Reference slider},Path=Value}" HorizontalTextAlignment="End" TextColor="Black" Text="{Binding _text}"></Label>