Net Maui how to get coordinats by pointergesture ?

Question

Net Maui how to get postion of coordinats by pointergesture or other way ? Android and Ios

I realized that pointergesture is not working on android..Any solution ?

Answer 1

Hello,

Net Maui how to get postion of coordinats by pointergesture or other way ?

You can implement a RouteEffect like Xamarin.Forms and can reuse effects in .NET MAUI - .NET MAUI | Microsoft Learn.

For example, you can create a TouchEffect and implement android platform code about postion TouchAction like following code. As Note: I implement it for android platform, for iOS platform, you can refer to this GitHub demo

#if ANDROID
using Android.Views;
using AndroidX.ConstraintLayout.Core.Widgets;

#endif
using Microsoft.Maui.Controls.Platform;
using Microsoft.Maui.Platform;

public enum TouchActionType
{
    Entered,
    Pressed,
    Moved,
    Released,
    Exited,
    Cancelled
}
public class TouchActionEventArgs : EventArgs
{
    public TouchActionEventArgs(long id, TouchActionType type, Point location, bool isInContact)
    {
        Id = id;
        Type = type;
        Location = location;
        IsInContact = isInContact;
    }

   public long Id { private set; get; }

   public TouchActionType Type { private set; get; }

   public Point Location { private set; get; }

   public bool IsInContact { private set; get; }
}

public delegate void TouchActionEventHandler(object sender, TouchActionEventArgs args);

internal class TouchRoutingEffect : RoutingEffect
{
    public event TouchActionEventHandler TouchAction;


   public TouchRoutingEffect()
    {
    }

   public bool Capture { set; get; }

   public void OnTouchAction(Element element, TouchActionEventArgs args)
    {
        TouchAction?.Invoke(element, args);
    }
}


#if ANDROID
internal class TouchPlatformEffect : PlatformEffect
{
    Android.Views.View view;
    Element formsElement;
    TouchRoutingEffect libTouchEffect;
    bool capture;
    Func<double, double> fromPixels;
    int[] twoIntArray = new int[2];

   static Dictionary<Android.Views.View, TouchPlatformEffect> viewDictionary =
        new Dictionary<Android.Views.View, TouchPlatformEffect>();

   static Dictionary<int, TouchPlatformEffect> idToEffectDictionary =
        new Dictionary<int, TouchPlatformEffect>();
    
    protected override void OnAttached()
    {
        // Get the Android View corresponding to the Element that the effect is attached to
        view = Control == null ? Container : Control;


       // Get access to the TouchEffect class in the .NET Standard library
        TouchRoutingEffect touchEffect =
            (TouchRoutingEffect)Element.Effects.
                FirstOrDefault(e => e is TouchRoutingEffect);

       if (touchEffect != null && view != null)
        {
            viewDictionary.Add(view, this);

           formsElement = Element;

           libTouchEffect = touchEffect;

           // Save fromPixels function
            fromPixels = view.Context.FromPixels;

           // Set event handler on View
            view.Touch += OnTouch;
        }
    }

   protected override void OnDetached()
    {
        if (viewDictionary.ContainsKey(view))
        {
            viewDictionary.Remove(view);
            view.Touch -= OnTouch;
        }
    }

   void OnTouch(object sender, Android.Views.View.TouchEventArgs args)
    {
        // Two object common to all the events
        Android.Views.View senderView = sender as Android.Views.View;
        MotionEvent motionEvent = args.Event;

       // Get the pointer index
        int pointerIndex = motionEvent.ActionIndex;

       // Get the id that identifies a finger over the course of its progress
        int id = motionEvent.GetPointerId(pointerIndex);
        senderView.GetLocationOnScreen(twoIntArray);
        Point screenPointerCoords = new Point(twoIntArray[0] + motionEvent.GetX(pointerIndex),
                                              twoIntArray[1] + motionEvent.GetY(pointerIndex));


        // Use ActionMasked here rather than Action to reduce the number of possibilities
        switch (args.Event.ActionMasked)
        {
            case MotionEventActions.Down:
            case MotionEventActions.PointerDown:
                FireEvent(this, id, TouchActionType.Pressed, screenPointerCoords, true);

               idToEffectDictionary.Add(id, this);
               capture = libTouchEffect.Capture;
                break;
           case MotionEventActions.Move:
                // Multiple Move events are bundled, so handle them in a loop
                for (pointerIndex = 0; pointerIndex < motionEvent.PointerCount; pointerIndex++)
                {
                    id = motionEvent.GetPointerId(pointerIndex);
                   if (capture)
                    {
                        senderView.GetLocationOnScreen(twoIntArray);
                       screenPointerCoords = new Point(twoIntArray[0] + motionEvent.GetX(pointerIndex),
                                                        twoIntArray[1] + motionEvent.GetY(pointerIndex));

                       FireEvent(this, id, TouchActionType.Moved, screenPointerCoords, true);
                    }
                    else
                    {
                        CheckForBoundaryHop(id, screenPointerCoords);




                       if (idToEffectDictionary[id] != null)
                        {
                            FireEvent(idToEffectDictionary[id], id, TouchActionType.Moved, screenPointerCoords, true);
                        }
                    }
                }
                break;

           case MotionEventActions.Up:
            case MotionEventActions.Pointer1Up:
                if (capture)
                {
                    FireEvent(this, id, TouchActionType.Released, screenPointerCoords, false);
                }
                else
                {
                    CheckForBoundaryHop(id, screenPointerCoords);
                   if (idToEffectDictionary[id] != null)
                    {
                        FireEvent(idToEffectDictionary[id], id, TouchActionType.Released, screenPointerCoords, false);
                    }
                }
                idToEffectDictionary.Remove(id);
                break;




           case MotionEventActions.Cancel:
                if (capture)
                {
                    FireEvent(this, id, TouchActionType.Cancelled, screenPointerCoords, false);
                }
                else
                {
                    if (idToEffectDictionary[id] != null)
                    {
                        FireEvent(idToEffectDictionary[id], id, TouchActionType.Cancelled, screenPointerCoords, false);
                    }
                }
                idToEffectDictionary.Remove(id);
                break;
        }
    }

   void CheckForBoundaryHop(int id, Point pointerLocation)
    {
        TouchPlatformEffect touchEffectHit = null;
       foreach (Android.Views.View view in viewDictionary.Keys)
        {
            // Get the view rectangle
            try
            {
                view.GetLocationOnScreen(twoIntArray);
            }
            catch // System.ObjectDisposedException: Cannot access a disposed object.
            {
                continue;
            }
            Rectangle viewRect = new Rectangle();
            viewRect.SetBounds(twoIntArray[0], twoIntArray[1], view.Width, view.Height);
            if (viewRect.Contains((int)pointerLocation.X,(int)pointerLocation.Y))
            {
                touchEffectHit = viewDictionary[view];
            }
        }

       if (touchEffectHit != idToEffectDictionary[id])
        {
            if (idToEffectDictionary[id] != null)
            {
                FireEvent(idToEffectDictionary[id], id, TouchActionType.Exited, pointerLocation, true);
            }
            if (touchEffectHit != null)
            {
                FireEvent(touchEffectHit, id, TouchActionType.Entered, pointerLocation, true);
            }
            idToEffectDictionary[id] = touchEffectHit;
        }
    }

   void FireEvent(TouchPlatformEffect touchEffect, int id, TouchActionType actionType, Point pointerLocation, bool isInContact)
    {
        // Get the method to call for firing events
        Action<Element, TouchActionEventArgs> onTouchAction = touchEffect.libTouchEffect.OnTouchAction;

       // Get the location of the pointer within the view
        touchEffect.view.GetLocationOnScreen(twoIntArray);
        double x = pointerLocation.X - twoIntArray[0];
        double y = pointerLocation.Y - twoIntArray[1];
        Point point = new Point(fromPixels(x), fromPixels(y));

       // Call the method
        onTouchAction(touchEffect.formsElement,
            new TouchActionEventArgs(id, actionType, point, isInContact));
    }
}
#elif IOS
internal class TouchPlatformEffect : PlatformEffect
{
    protected override void OnAttached()
    {
        // Customize the control here
    }

   protected override void OnDetached()
    {
        // Cleanup the control customization here
    }
}
#endif

Then, Register this toucheffect in the MauiProgram.cs, I register it for android, that is same for iOS.

 public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
           .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            }).ConfigureEffects(effects =>
            {
#if ANDROID
                effects.Add<TouchRoutingEffect, TouchPlatformEffect>();
#endif
            }

In the end, you can use this toucheffect and get the touch position. I add this touchRoutingEffect to the outside stacklayout.

<VerticalStackLayout  >
        <VerticalStackLayout.Effects>
            <local:TouchRoutingEffect TouchAction="TouchRoutingEffect_TouchAction"></local:TouchRoutingEffect>
        </VerticalStackLayout.Effects>

Then We can get the position in the background code.

private void TouchRoutingEffect_TouchAction(object sender, TouchActionEventArgs args)
    { 
        Point res=args.Location;
        Console.WriteLine(res.X+" ===="+res.Y.ToString());
    }

Best Regards,

Leon Lu

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Answer 2

android and iOS do not have a physical pointer (a pixel level selector). you probably want to use tap and swipe which is done with a finger.