Xamarin.Les formulaires Bouton Enfoncé & Libéré de l'Événement

Cela peut aussi être fait avec un effet au lieu d'une véritable moteur de rendu personnalisé. Voir ce post pour une explication de comment le faire:

https://alexdunn.org/2017/12/27/xamarin-tip-xamarin-forms-long-press-effect/

En cas que le post ne va jamais loin, voici le code que vous pouvez mettre en œuvre:

Dans le projet partagé:

///<summary>
///Long pressed effect. Used for invoking commands on long press detection cross platform
///</summary>
public class LongPressedEffect : RoutingEffect
{
    public LongPressedEffect() : base("MyApp.LongPressedEffect")
    {
    }

    public static readonly BindableProperty CommandProperty = BindableProperty.CreateAttached("Command", typeof(ICommand), typeof(LongPressedEffect), (object)null);
    public static ICommand GetCommand(BindableObject view)
    {
        return (ICommand)view.GetValue(CommandProperty);
    }

    public static void SetCommand(BindableObject view, ICommand value)
    {
        view.SetValue(CommandProperty, value);
    }


    public static readonly BindableProperty CommandParameterProperty = BindableProperty.CreateAttached("CommandParameter", typeof(object), typeof(LongPressedEffect), (object)null);
    public static object GetCommandParameter(BindableObject view)
    {
        return view.GetValue(CommandParameterProperty);
    }

    public static void SetCommandParameter(BindableObject view, object value)
    {
        view.SetValue(CommandParameterProperty, value);
    }
}

Dans Android:

[assembly: ResolutionGroupName("MyApp")]
[assembly: ExportEffect(typeof(AndroidLongPressedEffect), "LongPressedEffect")]
namespace AndroidAppNamespace.Effects
{
///<summary>
///Android long pressed effect.
///</summary>
public class AndroidLongPressedEffect : PlatformEffect
{
private bool _attached;
///<summary>
///Initializer to avoid linking out
///</summary>
public static void Initialize() { }
///<summary>
///Initializes a new instance of the
///<see cref="T:Yukon.Application.AndroidComponents.Effects.AndroidLongPressedEffect"/> class.
///Empty constructor required for the odd Xamarin.Forms reflection constructor search
///</summary>
public AndroidLongPressedEffect()
{
}
///<summary>
///Apply the handler
///</summary>
protected override void OnAttached()
{
//because an effect can be detached immediately after attached (happens in listview), only attach the handler one time.
if (!_attached)
{
if (Control != null)
{
Control.LongClickable = true;
Control.LongClick += Control_LongClick;
}
else
{
Container.LongClickable = true;
Container.LongClick += Control_LongClick;
}
_attached = true;
}
}
///<summary>
///Invoke the command if there is one
///</summary>
///<param name="sender">Sender.</param>
///<param name="e">E.</param>
private void Control_LongClick(object sender, Android.Views.View.LongClickEventArgs e)
{
Console.WriteLine("Invoking long click command");
var command = LongPressedEffect.GetCommand(Element);
command?.Execute(LongPressedEffect.GetCommandParameter(Element));
}
///<summary>
///Clean the event handler on detach
///</summary>
protected override void OnDetached()
{
if (_attached)
{
if (Control != null)
{
Control.LongClickable = true;
Control.LongClick -= Control_LongClick;
}
else
{
Container.LongClickable = true;
Container.LongClick -= Control_LongClick;
}
_attached = false;
}
}
}
}

Dans iOS:

[assembly: ResolutionGroupName("MyApp")]
[assembly: ExportEffect(typeof(iOSLongPressedEffect), "LongPressedEffect")]
namespace iOSNamespace.Effects
{
///<summary>
///iOS long pressed effect
///</summary>
public class iOSLongPressedEffect : PlatformEffect
{
private bool _attached;
private readonly UILongPressGestureRecognizer _longPressRecognizer;
///<summary>
///Initializes a new instance of the
///<see cref="T:Yukon.Application.iOSComponents.Effects.iOSLongPressedEffect"/> class.
///</summary>
public iOSLongPressedEffect()
{
_longPressRecognizer = new UILongPressGestureRecognizer(HandleLongClick);
}
///<summary>
///Apply the handler
///</summary>
protected override void OnAttached()
{
//because an effect can be detached immediately after attached (happens in listview), only attach the handler one time
if (!_attached)
{
Container.AddGestureRecognizer(_longPressRecognizer);
_attached = true;
}
}
///<summary>
///Invoke the command if there is one
///</summary>
private void HandleLongClick()
{
var command = LongPressedEffect.GetCommand(Element);
command?.Execute(LongPressedEffect.GetCommandParameter(Element));
}
///<summary>
///Clean the event handler on detach
///</summary>
protected override void OnDetached()
{
if (_attached)
{
Container.RemoveGestureRecognizer(_longPressRecognizer);
_attached = false;
}
}
}
}

En XAML

<Label Text="Long Press Me!" effects:LongPressedEffect.Command="{Binding ShowAlertCommand}" effects:LongPressedEffect.CommandParameter="{Binding .}">
<Label.Effects>
<effects:LongPressedEffect />
</Label.Effects>
</Label>

Depuis Xamarin.Les formes 2.4.0, Les événements Enfoncé et Publié sont offerts à l'extérieur de la boîte (voir PR).

Remarque: afin de parvenir à un Talkie-Walkie effet, vous pourriez vouloir utiliser Device.BeginInvokeOnMainThread (ou via le Prisme de l' IDeviceService) pour invoquer les mesures de sorte que le Released événement seront appelés, sinon le thread d'INTERFACE utilisateur peut être bloqué.

Alternativement, vous pouvez déclarer les gestionnaires d'événements comme async et await vos invocations, pour garder le thread d'INTERFACE utilisateur inoccupée.