Xamarin.Forms Button长按事件

Posted 2020-10-23 Devin.Zhou

Xamarin.Forms Button长按事件

在平时的开发中，我们经常遇到需要Button能够拥有长按事件，但是在Xamarin.Forms中Button并没有该事件，

此时我们如何来实现呢？

我们知道在Xamarin.Forms中可以通过CustomRenderer来根据不同平台各自处理。

这里我们即便用这个方法来实现长按事件：

android的长按事件：

[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
                        };
                    }
                }
    }
}

ios长按事件处理：

[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;
        }
    }
}