Xamarin.Forms - 按钮按下 &发布活动 [英] Xamarin.Forms - Button Pressed & Released Event

问题描述

我想在按钮按下和释放时触发我的事件，但我只能在 Xamarin.Forms 中找到 Click 事件.

I want to my event to trigger when button pressed and released, but I can only find Click event in Xamarin.Forms.

我相信必须有一些解决方法才能获得此功能.我的基本需求是按下按钮时启动一个过程，释放时停止.这似乎是一个非常基本的功能，但 Xamarin.Forms 现在没有.

I believe there must be some work around to get this functionality. My basic need is to start a process when button is pressed and stop when released. It seems to be a very basic feature but Xamarin.Forms doesn't have it right now.

我在按钮上尝试了 TapGestureRecognizer，但按钮仅触发点击事件.

I tried TapGestureRecognizer on button, but button is firing only click event.

MyButton.Clicked += (sender, args) =>
{
  Log.V(TAG, "CLICKED");
};

var tapGestureRecognizer = new TapGestureRecognizer();
tapGestureRecognizer.Tapped += (s, e) => {
    Log.V(TAG, "TAPPED");
};
MyButton.GestureRecognizers.Add(tapGestureRecognizer);

请记住，我需要将这些事件同时在 Android 和 iOS 中运行.

Keep in mind that I need those events to be working in Android and iOS togather.

推荐答案

最后我得到了@Jason 建议的解决方案.来了……

Finally I got the solution suggested by @Jason. Here we go...

1. 在PCL项目中创建Xamarin.Forms.Button的子类，带事件处理能力

1. Create sub class of Xamarin.Forms.Button in PCL project, with event handling capability

public class CustomButton : Button
{
    public event EventHandler Pressed;
    public event EventHandler Released;

    public virtual void OnPressed()
    {
      Pressed?.Invoke(this, EventArgs.Empty);
    }

    public virtual void OnReleased()
    {
      Released?.Invoke(this, EventArgs.Empty);
    }
}

在各自的项目中创建特定于平台的按钮渲染器

Create platform specific button renderer in respective project

对于安卓

[assembly: ExportRenderer(typeof(Button), typeof(CustomButtonRenderer))]
namespace WalkieTalkie.Droid.Renderer
{
    public class CustomButtonRenderer : ButtonRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
        {
            base.OnElementChanged(e);

            var customButton = e.NewElement as CustomButton;

            var thisButton = Control as Android.Widget.Button;
            thisButton.Touch += (object sender, TouchEventArgs args) =>
            {
                if (args.Event.Action == MotionEventActions.Down)
                {
                    customButton.OnPressed();
                }
                else if (args.Event.Action == MotionEventActions.Up)
                {
                    customButton.OnReleased();
                }
            };
        }
    }
}

IOS 版

[assembly: ExportRenderer(typeof(CustomButton), typeof(CustomButtonRenderer))]
namespace WalkieTalkie.iOS.Renderer
{
    public class CustomButtonRenderer : ButtonRenderer
    {
        protected override void    OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
        {
            base.OnElementChanged(e);

            var customButton = e.NewElement as CustomButton;

            var thisButton = Control as UIButton;
            thisButton.TouchDown += delegate
            {
                customButton.OnPressed();
            };
            thisButton.TouchUpInside += delegate
            {
                customButton.OnReleased();
            };
        }
    }
}

在页面中实例化自定义按钮

Instantiate your custom button in your page

var myButton = new CustomButton
{
    Text = "CustomButton",
    HorizontalOptions = LayoutOptions.FillAndExpand
};
myButton.Pressed += (sender, args) =>
{
    System.Diagnostics.Debug.WriteLine("Pressed");
};
myButton.Released += (sender, args) =>
{
     System.Diagnostics.Debug.WriteLine("Pressed");
};

希望这对某人有所帮助:)

Hope this help someone :)

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