Xamarin.Forms 监听Button的按下、释放事件

工作中遇到这样的一个需求，模仿微信发生语音功能，需要实现按钮按下开始录音，按钮释放录音结束，

Xamarin.Forms中Button没有这样的事件，那么我们如何实现对Button按下，释放两个事件的监听呢？

当然这里我们再次用到了CustomRenderer，一旦遇到Xamrin.Forms无法实现的某些功能，我们就可以

通过CustomRenderer来处理。

首先：我们自定义一个VoiceRecordButton继承于Button

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Diagnostics;
 4 using System.Text;
 5 using System.Windows.Input;
 6 using Xamarin.Forms;
 7
 8 namespace XFPractice.CustomView
 9 {
10     public class VoiceRecordButton: Button
11     {
12
13         public ICommand StartCommand { get; set; }
14         public ICommand EndCommand { get; set; }
15
16         public VoiceRecordButton()
17         {
18             StartCommand = new Command(()=> {
19                 Debug.WriteLine(" StartCommand =========== ");
20             });
21
22             EndCommand = new Command(() => {
23                 Debug.WriteLine(" EndCommand =========== ");
24             });
25         }
26
27     }
28 }

然后分别编写各个平台自己的VoiceRecordButtonRenderer：

Android：

通过IOnTouchListener来监听用户对Button的操作。

 1 using Android.Views;
 2 using XFPractice.CustomView;
 3 using XFPractice.Droid.Renderers;
 4 using Xamarin.Forms;
 5 using Xamarin.Forms.Platform.Android;
 6 using static Android.Views.View;
 7
 8 [assembly: ExportRenderer(typeof(VoiceRecordButton), typeof(VoiceRecordButtonRenderer))]
 9 namespace XFPractice.Droid.Renderers
10 {
11     public class VoiceRecordButtonRenderer:ButtonRenderer,IOnTouchListener
12     {
13         VoiceRecordButton view;
14
15         public bool OnTouch(Android.Views.View v, MotionEvent e)
16         {
17             switch(e.Action)
18             {
19                 case MotionEventActions.Down:
20                     view?.StartCommand?.Execute("");
21                     break;
22                 case MotionEventActions.Up:
23                      view?.EndCommand?.Execute("");
24                     break;
25             }
26             return true;
27         }
28
29         protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
30         {
31             base.OnElementChanged(e);
32
33             Control.SetOnTouchListener(this);
34
35             if (e.NewElement != null)
36                 view = e.NewElement as VoiceRecordButton;
37         }
38
39     }
40 }

iOS:

通过对TouchDown、TouchUpInside、TouchUpOutside三个事件的处理。

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Diagnostics;
 4 using System.Linq;
 5 using System.Text;
 6
 7 using Foundation;
 8 using XFPractice.CustomView;
 9 using XFPractice.iOS.Renderers;
10 using UIKit;
11 using Xamarin.Forms;
12 using Xamarin.Forms.Platform.iOS;
13
14 [assembly: ExportRenderer(typeof(VoiceRecordButton), typeof(VoiceRecordButtonRenderer))]
15 namespace XFPractice.iOS.Renderers
16 {
17     public class VoiceRecordButtonRenderer : ButtonRenderer
18     {
19         VoiceRecordButton view;
20
21         public VoiceRecordButtonRenderer()
22         {
23
24         }
25
26
27         protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
28         {
29             base.OnElementChanged(e);
30
31             if (e.NewElement != null)
32                 view = e.NewElement as VoiceRecordButton;
33             Control.TouchDown += Control_TouchDown;
34             Control.TouchUpInside += Control_TouchUpInside;
35             Control.TouchUpOutside += Control_TouchUpOutside;
36         }
37
38         private void Control_TouchUpOutside(object sender, EventArgs e)
39         {
40             view?.EndCommand?.Execute("");
41         }
42
43         private void Control_TouchUpInside(object sender, EventArgs e)
44         {
45             view?.EndCommand?.Execute("");
46         }
47
48         private void Control_TouchDown(object sender, EventArgs e)
49         {
50             view?.StartCommand?.Execute("");
51         }
52     }
53 }

UWP:

UWP有一个Holding事件，但是对鼠标无效，只对触摸有效，这里我们采用了PointerEventHandler来处理。

 1 using XFPractice.CustomView;
 2 using XFPractice.UWP.Renderers;
 3 using System;
 4 using System.Collections.Generic;
 5 using System.Diagnostics;
 6 using System.Linq;
 7 using System.Text;
 8 using System.Threading.Tasks;
 9 using Windows.UI.Input;
10 using Windows.UI.Xaml.Input;
11 using Xamarin.Forms.Platform.UWP;
12
13 [assembly: ExportRenderer(typeof(VoiceRecordButton), typeof(VoiceRecordButtonRenderer))]
14 namespace XFPractice.UWP.Renderers
15 {
16     public class VoiceRecordButtonRenderer:ButtonRenderer
17     {
18         VoiceRecordButton view;
19
20
21         public VoiceRecordButtonRenderer()
22         {
23         }
24
25
26
27         protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
28         {
29             base.OnElementChanged(e);
30
31
32             if (e.NewElement != null)
33             {
34                 view = e.NewElement as VoiceRecordButton;
35             }
36             Control.AddHandler(PointerReleasedEvent, new PointerEventHandler(Control_PointerReleased), true);
37             Control.AddHandler(PointerPressedEvent, new PointerEventHandler(Control_PointerPressed), true);
38         }
39
40         private void Control_PointerPressed(object sender, PointerRoutedEventArgs e)
41         {
42             view?.StartCommand?.Execute("");
43         }
44
45         private void Control_PointerReleased(object sender, PointerRoutedEventArgs e)
46         {
47             view?.EndCommand?.Execute("");
48         }
49
50
51          }
52 }

这样我们就能监听Button的按下、和释放操作。

原文地址：https://www.cnblogs.com/devin_zhou/p/8414675.html