Scrollview 在 Xamarin Forms 中不起作用

我的 xamarin 表单应用程序中有以下布局:

I have following layout in my xamarin forms application:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:telerikInput="clr-namespace:Telerik.XamarinForms.Input;assembly=Telerik.XamarinForms.Input"
             xmlns:telerikPrimitives="clr-namespace:Telerik.XamarinForms.Primitives;assembly=Telerik.XamarinForms.Primitives"
             x:Class="DMGMobile.UserDetailPage">
    <ContentPage.ToolbarItems>
        <ToolbarItem Name="Save" Icon="settings.png" Clicked="Save"></ToolbarItem>
    </ContentPage.ToolbarItems>

    <ContentPage.Content>
        <ScrollView 
            Orientation="Vertical" 
            VerticalScrollBarVisibility="Always"
            VerticalOptions="FillAndExpand">
            <StackLayout
                VerticalOptions="FillAndExpand"
                Padding="10,0,10,0">

                <Label 
                    Text="Name"/>
                <telerikInput:RadEntry 
                    x:Name="User_Name"
                    BackgroundColor="White" 
                    WatermarkText="Name"
                    TextColor="Black"
                    WatermarkTextColor="#C0C0C0">
                    <telerikInput:RadEntry.Padding>
                        <OnPlatform x:TypeArguments="Thickness">
                            <On Platform="Android,UWP" Value="10,10,0,10" />
                            <On Platform="iOS" Value="10,10,0,20" />
                        </OnPlatform>
                    </telerikInput:RadEntry.Padding>
                    <telerikInput:RadEntry.BorderStyle>
                        <telerikInput:BorderStyle 
                            CornerRadius="8"
                            BorderColor="#257cc1"
                            BorderThickness="1" />
                    </telerikInput:RadEntry.BorderStyle>
                </telerikInput:RadEntry>

                <Label 
                    Text="Surname"/>
                <telerikInput:RadEntry 
                    x:Name="User_Vorname"
                    BackgroundColor="White" 
                    WatermarkText="Surname"
                    TextColor="Black"
                    WatermarkTextColor="#C0C0C0">
                    <telerikInput:RadEntry.Padding>
                        <OnPlatform x:TypeArguments="Thickness">
                            <On Platform="Android,UWP" Value="10,10,0,10" />
                            <On Platform="iOS" Value="10,10,0,20" />
                        </OnPlatform>
                    </telerikInput:RadEntry.Padding>
                    <telerikInput:RadEntry.BorderStyle>
                        <telerikInput:BorderStyle 
                        CornerRadius="8"
                        BorderColor="#257cc1"
                        BorderThickness="1" />
                    </telerikInput:RadEntry.BorderStyle>
                </telerikInput:RadEntry>

                <Label 
                    Text="Login"/>
                <telerikInput:RadEntry 
                    x:Name="User_Login"
                    BackgroundColor="White" 
                    WatermarkText="Login"
                    TextColor="Black"
                    WatermarkTextColor="#C0C0C0"
                    TextChanged="User_Login_TextChanged">
                    <telerikInput:RadEntry.Padding>
                        <OnPlatform x:TypeArguments="Thickness">
                            <On Platform="Android,UWP" Value="10,10,0,10" />
                            <On Platform="iOS" Value="10,10,0,20" />
                        </OnPlatform>
                    </telerikInput:RadEntry.Padding>
                    <telerikInput:RadEntry.BorderStyle>
                        <telerikInput:BorderStyle 
                        CornerRadius="8"
                        BorderColor="#257cc1"
                        BorderThickness="1" />
                    </telerikInput:RadEntry.BorderStyle>
                </telerikInput:RadEntry>

                <Label 
                    Text="Pass"/>
                <telerikInput:RadEntry 
                    x:Name="User_Password"
                    BackgroundColor="Transparent" 
                    WatermarkText="Pass"
                    TextColor="Black"
                    WatermarkTextColor="#C0C0C0"
                    TextChanged="User_Login_TextChanged">
                    <telerikInput:RadEntry.Padding>
                        <OnPlatform x:TypeArguments="Thickness">
                            <On Platform="Android,UWP" Value="10,10,0,10" />
                            <On Platform="iOS" Value="10,10,0,20" />
                        </OnPlatform>
                    </telerikInput:RadEntry.Padding>
                    <telerikInput:RadEntry.BorderStyle>
                        <telerikInput:BorderStyle 
                        CornerRadius="8"
                        BorderColor="#257cc1"
                        BorderThickness="1" />
                    </telerikInput:RadEntry.BorderStyle>
                </telerikInput:RadEntry>

                <telerikPrimitives:RadCheckBox 
                    x:Name="User_IsAdmin" />
                <Label 
                    Text="Is admin}"/>

            </StackLayout>
        </ScrollView>
    </ContentPage.Content>
</ContentPage>

问题是 ScrollView 不起作用.尽管 VerticalScrollBarVisibility 设置为 Always，但我什至看不到垂直滚动条.没有键盘的页面看起来不错，但如果显示键盘，则位于页面底部的一些输入被隐藏，我无法滚动以访问它们.

The problem is that ScrollView is not working. I can't even see vertical scrollbar although VerticalScrollBarVisibility is set to Always. The page looks nice without keyboard, but if keyboard shown then some inputs placed on the bottom of the page are hidden and I can't scroll to reach them.

我在这里错过了什么令人讨厌的东西吗?

Am I missing something obious here?