如何在Xamarin Forms中做出长按手势?

问题描述

能否让我知道如何在Xamarin Forms应用程序中识别长按手势?

Could you please let me know how can I recognize long press gesture in Xamarin Forms application?

使用TapGestureRecognizer

TapGestureRecognizer imageTap = new TapGestureRecognizer();
imageTap.Tapped += (sender, args) => this.OnClickImage;
image.GestureRecognizers.Add(imageTap);

但是我不知道如何根据此来自xamarin论坛的线程

But I don't know how to make long press gesture according to this thread from xamarin forum

它看起来应该像这样，但是不起作用.

It should looks something like this, but it does not work.

var dumpParam = new RelayGesture((g, x) => DisplayAlert("Title", "Hello message", "Cancel"));

book.Cover.SetValue(Gestures.InterestsProperty, new GestureCollection() {
    new GestureInterest
        {
            GestureType = GestureType.LongPress
            GestureCommand = // what should I set?
            GestureParameter = dumpParam
        }
 });

如何设置我的自定义处理程序方法?

How to set my custom handler method?

推荐答案

浏览互联网我找到了解决方案.您应该复制几个步骤.

Surfing the internet I found the solution. There are few steps which you should reproduce.

1) 继承需要手势的控件(即，如果要向Xamarin.Forms.Image添加手势，请创建自己的ImageWithLongPressGesture类).

1) Inherit the control you need the gestures on (i.e. if you want to add gesture to Xamarin.Forms.Image, create you own ImageWithLongPressGesture class).

public class ImageWithLongPressGesture : Xamarin.Forms.Image
{
    public EventHandler LongPressActivated;

    public void HandleLongPress(object sender, EventArgs e)
    {
        //Handle LongPressActivated Event
    }
}

2)公开公共事件以获取所需的手势.

3)为每个平台创建一个渲染器.

4)在渲染器中，处理手势并将其显示在控件上.

[assembly: ExportRenderer(typeof(ImageWithLongPressGesture), typeof(LongPressGestureRecognizerImageRenderer))]
namespace App1.Droid.DroidRenderers
{
    public class LongPressGestureRecognizerImageRenderer : ImageRenderer
    {
        ImageWithLongPressGesture view;

        public LongPressGestureRecognizerImageRenderer()
        {
            this.LongClick += (sender, args) => {
                Toast.MakeText(this.Context, "Long press is activated.", ToastLength.Short).Show();
            };
        }

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

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

此解决方案是和 rel ="nofollow noreferrer">触摸和手势"演示.

This solution is a hybrid of answer on xamarin forms forum and Touch and Gestures presentation by Telerik.

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