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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Xamarin.Forms.Controls
{
public class PanGestureGalleryPage : ContentPage
{
public class PanCompleteArgs : EventArgs
{
public PanCompleteArgs(string message) { Message = message; }
public string Message
{
get; private set;
}
}
public class PanContainer : ContentView
{
double _x, _y;
double _currentScale = 1;
public EventHandler<PanCompleteArgs> PanCompleted;
public PanContainer()
{
GestureRecognizers.Add(GetPinch());
GestureRecognizers.Add(GetPan());
}
PanGestureRecognizer GetPan()
{
var pan = new PanGestureRecognizer();
pan.PanUpdated += (s, e) =>
{
switch (e.StatusType)
{
case GestureStatus.Running:
Content.TranslationX = e.TotalX;
Content.TranslationY = e.TotalY;
break;
case GestureStatus.Completed:
_x = Content.TranslationX;
_y = Content.TranslationY;
PanCompleted?.Invoke(s, new PanCompleteArgs($"x: {_x}, y: {_y}"));
break;
}
};
return pan;
}
PinchGestureRecognizer GetPinch()
{
var pinch = new PinchGestureRecognizer();
double xOffset = 0;
double yOffset = 0;
double startScale = 1;
pinch.PinchUpdated += (sender, e) =>
{
if (e.Status == GestureStatus.Started)
{
startScale = Content.Scale;
Content.AnchorX = Content.AnchorY = 0;
}
if (e.Status == GestureStatus.Running)
{
_currentScale += (e.Scale - 1) * startScale;
_currentScale = Math.Max(1, _currentScale);
var renderedX = Content.X + xOffset;
var deltaX = renderedX / Width;
var deltaWidth = Width / (Content.Width * startScale);
var originX = (e.ScaleOrigin.X - deltaX) * deltaWidth;
var renderedY = Content.Y + yOffset;
var deltaY = renderedY / Height;
var deltaHeight = Height / (Content.Height * startScale);
var originY = (e.ScaleOrigin.Y - deltaY) * deltaHeight;
double targetX = xOffset - (originX * Content.Width) * (_currentScale - startScale);
double targetY = yOffset - (originY * Content.Height) * (_currentScale - startScale);
Content.TranslationX = targetX.Clamp(-Content.Width * (_currentScale - 1), 0);
Content.TranslationY = targetY.Clamp(-Content.Height * (_currentScale - 1), 0);
Content.Scale = _currentScale;
}
if (e.Status == GestureStatus.Completed)
{
xOffset = Content.TranslationX;
yOffset = Content.TranslationY;
}
};
return pinch;
}
}
public PanGestureGalleryPage()
{
var box = new Image
{
BackgroundColor = Color.Gray,
WidthRequest = 2000,
HeightRequest = 2000,
VerticalOptions = LayoutOptions.Center,
HorizontalOptions = LayoutOptions.Center
};
var label = new Label { Text = "Use two fingers to pinch. Use one finger to pan." };
var panme = new PanContainer { Content = box };
panme.PanCompleted += (s, e) =>
{
label.Text = e.Message;
};
Content = new StackLayout { Children = { label, panme }, Padding = new Thickness(20) };
}
}
}
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