Xamarin Layout can't receive focus - forms

Question

I'm trying to create a compound view component in Xamarin Forms called FormElement which is composed of two labels and an Entry:
<?xml version="1.0" encoding="UTF-8"?>
<StackLayout xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:custom="clr-namespace:Mynamespace;assembly=Mynamespace"
x:Class="Mynamespace.Components.FormEntry">
<StackLayout Orientation="Horizontal">
<Label x:Name="formRequiredStar"
IsVisible="{Binding IsRequired}"
Text="*" TextColor="Red"
FontSize="15"
FontAttributes="Bold"
Margin="-12,0,0,0"
HorizontalOptions="Start" />
<Label x:Name="formLabel"
HorizontalOptions="Start"
Text="{Binding LabelText}"
TextColor="{Binding LabelTextColor}"
FontSize="{Binding LabelTextFontSize}"
FontAttributes="{Binding LabelTextFontStyle}" />
</StackLayout>
<Frame BorderColor="Black"
CornerRadius="7"
Padding="5,0"
Margin="0,-3,0,0"
HasShadow="false">
<Entry x:Name="mainEntry"
Keyboard="{Binding KeybdType}"
Placeholder="{Binding EntryPlaceHolder}"
TextColor="Black"
FontSize="Default"
HeightRequest="{Binding EntryHeight}" />
</Frame>
</StackLayout>
Next, I want to switch focus from the Entry to a "next" element when the user taps the DONE button, so I do:
namespace Mynamespace.Components
{
public partial class FormEntry : StackLayout
{
public VisualElement NextFocus
{
get { return (VisualElement)GetValue(NextFocusProperty); }
set { SetValue(NextFocusProperty, value); }
}
public static readonly BindableProperty NextFocusProperty =
BindableProperty.Create(nameof(NextFocus),
typeof(VisualElement),
typeof(FormEntry),
null,
Xamarin.Forms.BindingMode.OneWay);
public FormEntry()
{
InitializeComponent();
BindingContext = this;
mainEntry.Completed += (s, e) =>
{
if (NextFocus != null)
{
NextFocus.Focus();
}
};
}
}
}
Next, in order for a FormEntry to be the target of NextFocus, I tried adding
this.Focused += (s,e) => { mainEntry.Focus(); };
to the constructor, but the handler is never called, and I also tried overriding
public new void Focus() {
mainEntry.Focus();
}
but this method is never called. Layout classes are descended from VisualElement so they should inherit Focused. Is there something about Layout objects that I'm missing? I could understand that Layout objects aren't usually the target of focus, but the event handler is supposedly there so I ought to be able to use it.
Here's an example of how I utilize the FormEntry on a login screen:
<!-- Email -->
<controls:FormEntry x:Name="usernameEntry"
Margin="25,40,25,0"
IsRequired="true"
EntryHeight="40"
KeybdType="Email"
NextFocus="{x:Reference passwordEntry}"
LabelText="{il8n:Translate Emailorusername}"
EntryPlaceHolder="{il8n:Translate EnterUsername}">
</controls:FormEntry>
<!-- Password -->
<controls:FormEntry x:Name="passwordEntry"
Margin="25,0,25,0"
IsRequired="true"
EntryHeight="40"
LabelText="{il8n:Translate Password}"
EntryPlaceHolder="{il8n:Translate EnterPassword}" />

Answer 1

I think you have get the nextfocus element, you can get mainEntry from nextfocus, like this:
public FormEntry ()
{
InitializeComponent ();
BindingContext = this;
mainEntry.Completed += (s, e) =>
{
if (NextFocus != null)
{
FormEntry formentry = (FormEntry)NextFocus;
Entry entry = formentry.mainEntry;
entry.Focus();
}
};
}
Then you can find you will get focus.