Answers

• LeonLu Member, Xamarin Team Xamurai

  October 2020

  In android, you can create a custom renderer for your webwiew. then add SetOnTouchListener for Webview.

  assembly: ExportRenderer(typeof(Xamarin.Forms.WebView), typeof(MyWebviewRender))]
  namespace MyWebviewDemo.Droid
  {
      public class MyWebviewRender : WebViewRenderer
      {
          Context context;
          public MyWebviewRender(Context context) : base(context)
          {
               this.context = context;
          }
          protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
          {
              base.OnElementChanged(e);
              Control.Settings.JavaScriptEnabled = true;
              Control.Settings.SetAppCacheEnabled(true);
              Control.Settings.CacheMode = Android.Webkit.CacheModes.Normal;
              Control.Settings.SetRenderPriority(RenderPriority.High);
              Control.Settings.DomStorageEnabled = true;
  
              Control.SetOnTouchListener(new MyWebviewTouchListner(context));
          }
      }
  
      internal class MyWebviewTouchListner :Java.Lang.Object, Android.Views.View.IOnTouchListener
      {
          private Context context;
          GestureDetector gestureDetector;
          public MyWebviewTouchListner(Context context)
          {
              this.context = context;
  
               gestureDetector=    new GestureDetector(context, new GestureListener(this));
          }
  
          public bool OnTouch(Android.Views.View v, MotionEvent e)
          {
           return   gestureDetector.OnTouchEvent(e);
             // throw new NotImplementedException();
          }
      }
  
      internal class GestureListener : Java.Lang.Object, Android.Views.GestureDetector.IOnGestureListener
      {
          private MyWebviewTouchListner myWebviewTouchListner;
  
          public GestureListener(MyWebviewTouchListner myWebviewTouchListner)
          {
              this.myWebviewTouchListner = myWebviewTouchListner;
          }
  
          public bool OnDown(MotionEvent e)
          {
              return false;
          }
  
          public bool OnFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
          {
              bool result = false;
              try
              {
                  float diffY = e2.GetY() - e1.GetY();
                  float diffX = e2.GetX() - e1.GetX();
                  if (Math.Abs(diffX) > Math.Abs(diffY))
                  {
                      // You can customize these settings, so 30 is an example
                      if (Math.Abs(diffX) > 30 && Math.Abs(velocityX) > 30)
                      {
                          if (diffX > 0)
                          {
                              //  touchListener.onSwipeRight();
  
                              Toast.MakeText(Android.App.Application.Context, "onSwipeRight", ToastLength.Short).Show();
                          }
                          else
                          {
                              Toast.MakeText(Android.App.Application.Context, "onSwipeLeft", ToastLength.Short).Show();
                              //    touchListener.onSwipeLeft();
                          }
                          result = true;
                      }
                  }
                  else
                  {
                      result = false;
                  }
              }
              catch (Exception exception)
              {
  
              }
              return result;
          }
  
          public void OnLongPress(MotionEvent e)
          {
  
          }
  
          public bool OnScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
          {
              return false;
          }
  
          public void OnShowPress(MotionEvent e)
          {
  
          }
  
          public bool OnSingleTapUp(MotionEvent e)
          {
              return false;
          }
      }
     }
  }
  

  Here is running GIF.

  

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• biconix Member ✭✭

  October 2020

  thank you for this reply.
  unfortuantely, i do not understadn how to implement it. I seem to be missing libraries, such as for classes: WebViewRenderer, Control, GestureDetector , Java.Lang.Object, Android.Views.GestureDetector.IOnGestureListener, etc.

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• LeonLu Member, Xamarin Team Xamurai

  October 2020

  You do not missing libraries, you should create an custom renderer for your webview like following link. Above code is related to the android platform.
  https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/hybridwebview#create-the-custom-renderer-on-android

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