如何處理短按和長按按鈕

Question

我如何處理短按和長按按鈕？ 我需要對短按鈕單擊和長按鈕單擊上的特定操作進行一些特定操作。 我讀到了Gesture Listener，並嘗試將其實現到Android MainActivity.cs文件（MainActivity類）中。 但是在應用程序運行時我有異常。

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="Test.Page">
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="*"/>
      <RowDefinition Height="100"/>
    </Grid.RowDefinitions>
    <ListView x:Name="MyButton" Grid.Row="0" />
    <ScrollView Orientation="Horizontal" Grid.Row="1">
      <Label x:Name="MyLabel" HorizontalOptions="Center">...</Label>
    </ScrollView>
  </Grid>
</ContentPage>

Answer 1

要執行此操作，您可以使用按鈕的自定義渲染器。 每個平台都有自己的方式來處理當前未通過表單按鈕公開的長手勢。

在Android上：

[assembly: Xamarin.Forms.ExportRenderer (typeof (MyButton), typeof (MyButtonRenderer))]
namespace MyApp.Android
{   
    public class MyButtonRenderer : ButtonRenderer
    {
        protected override void OnElementChanged (ElementChangedEventArgs<global::Xamarin.Forms.Button> e)
                {
                    base.OnElementChanged (e);
                    if (e.OldElement == null) {
                        var nativeButton = Control;
                        nativeButton.LongClick += delegate {
                            //Do something
                        };
                    }
                }
    }
}

在iOS上：

[assembly:ExportRenderer (typeof(ButtonWithLongPressGesture), typeof(LongPressGestureRecognizerButtonRenderer))]
namespace SampleApp.iOS
{
    public class LongPressGestureRecognizerButtonRenderer : ButtonRenderer
    {
        ButtonWithLongPressGesture view;

        public ButtonPressGestureRecognizerImageRenderer ()
        {
            this.AddGestureRecognizer (new UILongPressGestureRecognizer ((longPress) => {
                if (longPress.State == UIGestureRecognizerState.Began) {
                    view.HandleLongPress(view, new EventArgs());
                }
            }));
        }

        protected override void OnElementChanged (ElementChangedEventArgs<Button> e)
        {
            base.OnElementChanged (e);

            if (e.NewElement != null)
                view = e.NewElement as ButtonWithLongPressGesture;
        }
    }
}