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using System;
using System.Collections.Generic;
using System.Linq;
using Android.Runtime;
using Android.Views;
using Object = Java.Lang.Object;
namespace Xamarin.Forms.Platform.Android
{
internal class InnerGestureListener : Object, GestureDetector.IOnGestureListener, GestureDetector.IOnDoubleTapListener
{
bool _isScrolling;
float _lastX;
float _lastY;
Func<bool> _scrollCompleteDelegate;
Func<float, float, int, bool> _scrollDelegate;
Func<int, bool> _scrollStartedDelegate;
Func<int, bool> _tapDelegate;
Func<int, IEnumerable<TapGestureRecognizer>> _tapGestureRecognizers;
public InnerGestureListener(Func<int, bool> tapDelegate, Func<int, IEnumerable<TapGestureRecognizer>> tapGestureRecognizers, Func<float, float, int, bool> scrollDelegate,
Func<int, bool> scrollStartedDelegate, Func<bool> scrollCompleteDelegate)
{
if (tapDelegate == null)
throw new ArgumentNullException("tapDelegate");
if (tapGestureRecognizers == null)
throw new ArgumentNullException("tapGestureRecognizers");
if (scrollDelegate == null)
throw new ArgumentNullException("scrollDelegate");
if (scrollStartedDelegate == null)
throw new ArgumentNullException("scrollStartedDelegate");
if (scrollCompleteDelegate == null)
throw new ArgumentNullException("scrollCompleteDelegate");
_tapDelegate = tapDelegate;
_tapGestureRecognizers = tapGestureRecognizers;
_scrollDelegate = scrollDelegate;
_scrollStartedDelegate = scrollStartedDelegate;
_scrollCompleteDelegate = scrollCompleteDelegate;
}
// This is needed because GestureRecognizer callbacks can be delayed several hundred milliseconds
// which can result in the need to resurrect this object if it has already been disposed. We dispose
// eagerly to allow easier garbage collection of the renderer
internal InnerGestureListener(IntPtr handle, JniHandleOwnership ownership) : base(handle, ownership)
{
}
internal void OnTouchEvent(MotionEvent e)
{
if (e.Action == MotionEventActions.Up)
EndScrolling();
else if (e.Action == MotionEventActions.Down)
SetStartingPosition(e);
else if (e.Action == MotionEventActions.Move)
StartScrolling(e);
}
bool GestureDetector.IOnDoubleTapListener.OnDoubleTap(MotionEvent e)
{
if (_tapDelegate == null || _tapGestureRecognizers == null)
return false;
return _tapDelegate(2);
}
bool GestureDetector.IOnDoubleTapListener.OnDoubleTapEvent(MotionEvent e)
{
return false;
}
bool GestureDetector.IOnDoubleTapListener.OnSingleTapConfirmed(MotionEvent e)
{
if (_tapDelegate == null || _tapGestureRecognizers == null)
return false;
// optimization: only wait for a second tap if there is a double tap handler
if (!HasDoubleTapHandler())
return false;
return _tapDelegate(1);
}
bool GestureDetector.IOnGestureListener.OnDown(MotionEvent e)
{
SetStartingPosition(e);
return false;
}
bool GestureDetector.IOnGestureListener.OnFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
{
EndScrolling();
return false;
}
void GestureDetector.IOnGestureListener.OnLongPress(MotionEvent e)
{
SetStartingPosition(e);
}
bool GestureDetector.IOnGestureListener.OnScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
{
if (e1 == null || e2 == null)
return false;
SetStartingPosition(e1);
return StartScrolling(e2);
}
void GestureDetector.IOnGestureListener.OnShowPress(MotionEvent e)
{
}
bool GestureDetector.IOnGestureListener.OnSingleTapUp(MotionEvent e)
{
if (_tapDelegate == null || _tapGestureRecognizers == null)
return false;
// optimization: do not wait for a second tap if there is no double tap handler
if (HasDoubleTapHandler())
return false;
return _tapDelegate(1);
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
_tapDelegate = null;
_tapGestureRecognizers = null;
_scrollDelegate = null;
_scrollStartedDelegate = null;
_scrollCompleteDelegate = null;
}
base.Dispose(disposing);
}
void SetStartingPosition(MotionEvent e1)
{
_lastX = e1.GetX();
_lastY = e1.GetY();
}
bool StartScrolling(MotionEvent e2)
{
if (_scrollDelegate == null)
return false;
if (!_isScrolling && _scrollStartedDelegate != null)
_scrollStartedDelegate(e2.PointerCount);
_isScrolling = true;
float totalX = e2.GetX() - _lastX;
float totalY = e2.GetY() - _lastY;
return _scrollDelegate(totalX, totalY, e2.PointerCount);
}
void EndScrolling()
{
if (_isScrolling && _scrollCompleteDelegate != null)
_scrollCompleteDelegate();
_isScrolling = false;
}
bool HasDoubleTapHandler()
{
return _tapGestureRecognizers(2).Any();
}
}
}
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