Xamarin.Formulare - Button Gedrückt & Event Veröffentlicht

Dies kann auch durchgeführt werden, mit dem Effekt, anstatt eine vollwertige custom renderer. Siehe diesen post für eine Erklärung, wie es zu tun:

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

Im Fall, dass die post immer geht Weg, hier ist der code, die Sie implementieren können:

Im freigegebenen Projekt:

///<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);
    }
}

In 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;
            }
        }
    }
}

In 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;
            }
        }

    }
}

In XAML

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

InformationsquelleAutor GBreen12

Seit Xamarin.Formen 2.4.0, Die Ereignisse Gedrückt und Veröffentlicht am angeboten aus der box (siehe PR).

Hinweis: um eine Walkie-Talkie-Effekt, den Sie verwenden möchten Device.BeginInvokeOnMainThread (oder über Prismen IDeviceService) aufrufen, konsequente Aktionen, so die Released - Ereignis aufgerufen, andernfalls wird der UI-thread blockiert werden können.

Alternativ können Sie erklären, die event-Handler als async und await Ihre Anrufung, damit der UI-thread unbesetzt.

InformationsquelleAutor Shimmy