I just did this today, but what I did was to create an effect and then a class with a bindable property. I based what I did on this blog. xamarin-forms-use-bindableproperty-in-effects Something I realized later is that this sample adds the effect only on a property change. Something you can do about that is to add both the effect as you would normally and then to also add the static class as mentioned in the article. In case you haven't done Bindable Properties before you do have to follow a specific naming convention for them to work.
I'm going to see if I can append more detail here. The comment replies don't leave enough characters to paste in the code samples.
Here's the effect
public class EntryScrubberEffect : RoutingEffect
{
public EntryScrubberEffect() : base("Xamarin.EntryScrubberEffect")
{
Carrier = FShippingCarrier.Unknown;
}
public EntryScrubberEffect(FShippingCarrier carrier) : base("Xamarin.EntryScrubberEffect")
{
Carrier = carrier;
}
public event ItemScannedEventHandler ItemScanned;
public void OnItemScanned(Element element, ItemScannedEventArgs args)
=> ItemScanned?.Invoke(element, args);
public FShippingCarrier Carrier { get; set; }
}
Here's the Bindable static class
public static class StaticEntryScrubberEffect
{
public static BindableProperty CarrierProperty = BindableProperty.CreateAttached(
"ShipCarrier",
typeof(FShippingCarrier),
typeof(StaticEntryScrubberEffect),
FShippingCarrier.Unknown,
propertyChanged: OnShipCarrierChanged);
static void OnShipCarrierChanged(BindableObject bindable, object oldValue, object newValue)
{
AttachEffect(bindable as Editor, (FShippingCarrier)newValue);
}
static void AttachEffect(Editor element, FShippingCarrier newValue)
{
var effect = element.Effects.FirstOrDefault(x => x is EntryScrubberEffect) as EntryScrubberEffect;
if (effect != null)
{
element.Effects.Remove(effect);
}
element.Effects.Add(new EntryScrubberEffect(newValue));
}
public static FShippingCarrier GetShipCarrier(BindableObject element)
{
return (FShippingCarrier)element.GetValue(CarrierProperty);
}
public static void SetShipCarrier(BindableObject element, FShippingCarrier value)
{
element.SetValue(CarrierProperty, value);
}
}
Here's the relavant Xaml
xmlns:ent="clr-namespace:Semita.Effects"
<Editor
Text="{Binding UserName}"
IsSpellCheckEnabled="False"
IsTextPredictionEnabled="False"
Unfocused="Entry_Unfocused"
TextColor="Black"
VerticalOptions="Center"
x:Name="UserNameField"
ent:StaticEntryScrubberEffect.Carrier="{Binding ImageColor}">
<Editor.Effects>
<ent:EntryScrubberEffect
ItemScanned="EntryScrubberEffect_ItemScanned"/>
</Editor.Effects>
</Editor>
Here's my implmentation off the effect
[assembly: Xamarin.Forms.ResolutionGroupName("Xamarin")]
[assembly: Xamarin.Forms.ExportEffect(typeof(EntryScrubberEffectUWP), "EntryScrubberEffect")]
namespace Semita.UWP
{
public class EntryScrubberEffectUWP : PlatformEffect
{
FrameworkElement frameworkElement;
Effects.EntryScrubberEffect effect;
Action<Element, ItemScannedEventArgs> onItemScanned;
public EntryScrubberEffectUWP()
{
}
protected override void OnAttached()
{
frameworkElement = Control == null ? Container : Control;
effect = (Effects.EntryScrubberEffect)Element?.Effects?.FirstOrDefault(e => e is Effects.EntryScrubberEffect);
if (effect != null && frameworkElement != null)
{
onItemScanned = effect.OnItemScanned;
}
Control.KeyDown += Control_KeyDown;
Control.PreviewKeyDown += Control_PreviewKeyDown;
}
private void Control_KeyDown(object sender, Windows.UI.Xaml.Input.KeyRoutedEventArgs e)
{
if (e.Key == Windows.System.VirtualKey.Enter)
{
var control = Control as TextBox;
if (control == null)
return;
onItemScanned(Element, new ItemScannedEventArgs(control.Text));
}
}
private void Control_PreviewKeyDown(object sender, Windows.UI.Xaml.Input.KeyRoutedEventArgs e)
{
if (e.Key == Windows.System.VirtualKey.Enter)
{
var control = Control as TextBox;
if (control == null)
return;
if (AllNumeric(control.Text))
control.Text = string.Empty;
else
onItemScanned(Element, new ItemScannedEventArgs(control.Text));
}
}
protected override void OnDetached()
{
var control = Control as TextBox;
if (control == null)
return;
control.PreviewKeyDown -= Control_PreviewKeyDown;
control.KeyDown -= Control_KeyDown;
}
public bool AllNumeric(string str)
{
try
{
foreach (char c in str)
{
if (c < '0' || c > '9')
return false;
}
return true;
}
catch
{
return false;
}
}
}
}
Please note that this code isn't complete yet or totally optimized. It's a work in progess that I just started yesterday. I just hope it gives you enough of an idea about how to potentially accomplish what you wanted to do using an effect. A custom renderer with some added bindable properties is also a completely valid way of accomplishing this task as well.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(35.2, 37%, 13%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EAJ%3C/text%3E%3C/svg%3E)