/
InnerGestureListener.cs
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/
InnerGestureListener.cs
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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
{
TapGestureHandler _tapGestureHandler;
PanGestureHandler _panGestureHandler;
SwipeGestureHandler _swipeGestureHandler;
bool _isScrolling;
float _lastX;
float _lastY;
bool _disposed;
Func<float, float, bool> _swipeDelegate;
Func<bool> _swipeCompletedDelegate;
Func<bool> _scrollCompleteDelegate;
Func<float, float, int, bool> _scrollDelegate;
Func<int, bool> _scrollStartedDelegate;
Func<int, Point, bool> _tapDelegate;
Func<int, IEnumerable<TapGestureRecognizer>> _tapGestureRecognizers;
public InnerGestureListener(TapGestureHandler tapGestureHandler, PanGestureHandler panGestureHandler, SwipeGestureHandler swipeGestureHandler)
{
if (tapGestureHandler == null)
{
throw new ArgumentNullException(nameof(tapGestureHandler));
}
if (panGestureHandler == null)
{
throw new ArgumentNullException(nameof(panGestureHandler));
}
if (swipeGestureHandler == null)
{
throw new ArgumentNullException(nameof(swipeGestureHandler));
}
_tapGestureHandler = tapGestureHandler;
_panGestureHandler = panGestureHandler;
_swipeGestureHandler = swipeGestureHandler;
_tapDelegate = tapGestureHandler.OnTap;
_tapGestureRecognizers = tapGestureHandler.TapGestureRecognizers;
_scrollDelegate = panGestureHandler.OnPan;
_scrollStartedDelegate = panGestureHandler.OnPanStarted;
_scrollCompleteDelegate = panGestureHandler.OnPanComplete;
_swipeDelegate = swipeGestureHandler.OnSwipe;
_swipeCompletedDelegate = swipeGestureHandler.OnSwipeComplete;
}
bool HasAnyGestures()
{
return _panGestureHandler.HasAnyGestures() || _tapGestureHandler.HasAnyGestures() || _swipeGestureHandler.HasAnyGestures();
}
// 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)
{
}
bool GestureDetector.IOnDoubleTapListener.OnDoubleTap(MotionEvent e)
{
if (_disposed)
return false;
if (HasDoubleTapHandler())
{
return _tapDelegate(2, new Point(e.GetX(), e.GetY()));
}
if (HasSingleTapHandler())
{
// If we're registering double taps and we don't actually have a double-tap handler,
// but we _do_ have a single-tap handler, then we're really just seeing two singles in a row
// Fire off the delegate for the second single-tap (OnSingleTapUp already did the first one)
return _tapDelegate(1, new Point(e.GetX(), e.GetY()));
}
return false;
}
bool GestureDetector.IOnDoubleTapListener.OnDoubleTapEvent(MotionEvent e)
{
return false;
}
bool GestureDetector.IOnGestureListener.OnDown(MotionEvent e)
{
SetStartingPosition(e);
if (HasAnyGestures())
{
// If we have any gestures to listen for, we need to return true to show we're interested in the rest
// of the events.
return true;
}
// Since we don't have any gestures we're listening for, we return false to show we're not interested
// and let parent controls have a whack at the events
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 (_disposed)
return false;
if (HasDoubleTapHandler())
{
// Because we have a handler for double-tap, we need to wait for
// OnSingleTapConfirmed (to verify it's really just a single tap) before running the delegate
return false;
}
// A single tap has occurred and there's no handler for double tap to worry about,
// so we can go ahead and run the delegate
return _tapDelegate(1, new Point(e.GetX(), e.GetY()));
}
bool GestureDetector.IOnDoubleTapListener.OnSingleTapConfirmed(MotionEvent e)
{
if (_disposed)
return false;
if (!HasDoubleTapHandler())
{
// We're not worried about double-tap, so OnSingleTapUp has already run the delegate
// there's nothing for us to do here
return false;
}
// Since there was a double-tap handler, we had to wait for OnSingleTapConfirmed;
// Now that we're sure it's a single tap, we can run the delegate
return _tapDelegate(1, new Point(e.GetX(), e.GetY()));
}
protected override void Dispose(bool disposing)
{
if (_disposed)
{
return;
}
_disposed = true;
if (disposing)
{
_panGestureHandler = null;
_swipeGestureHandler = null;
_tapGestureHandler = null;
_tapDelegate = null;
_tapGestureRecognizers = null;
_scrollDelegate = null;
_scrollStartedDelegate = null;
_scrollCompleteDelegate = null;
_swipeDelegate = null;
_swipeCompletedDelegate = 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) || _swipeDelegate(totalX, totalY);
}
internal void EndScrolling()
{
if (_isScrolling && _scrollCompleteDelegate != null)
_scrollCompleteDelegate();
if (_isScrolling && _swipeCompletedDelegate != null)
_swipeCompletedDelegate();
_isScrolling = false;
}
bool HasDoubleTapHandler()
{
if (_tapGestureRecognizers == null)
return false;
return _tapGestureRecognizers(2).Any();
}
bool HasSingleTapHandler()
{
if (_tapGestureRecognizers == null)
return false;
return _tapGestureRecognizers(1).Any();
}
}
}