public virtual bool OnTouchEvent(Android.Views.MotionEvent ev)
{
switch (ev.Action)
{
case MotionEventActions.Down:
{
mVelocityTracker = VelocityTracker.Obtain();
if (null != mVelocityTracker)
{
mVelocityTracker.AddMovement(ev);
}
else
{
Log.Info(LOG_TAG, "Velocity tracker is null");
}
mLastTouchX = GetActiveX(ev);
mLastTouchY = GetActiveY(ev);
mIsDragging = false;
break;
}
case MotionEventActions.Move: {
float x = GetActiveX(ev);
float y = GetActiveY(ev);
float dx = x - mLastTouchX, dy = y - mLastTouchY;
if (!mIsDragging)
{
// Use Pythagoras to see if drag length is larger than
// touch slop
mIsDragging = FloatMath.Sqrt((dx * dx) + (dy * dy)) >= mTouchSlop;
}
if (mIsDragging)
{
mListener.OnDrag(dx, dy);
mLastTouchX = x;
mLastTouchY = y;
if (null != mVelocityTracker)
{
mVelocityTracker.AddMovement(ev);
}
}
break;
}
case MotionEventActions.Cancel: {
// Recycle Velocity Tracker
if (null != mVelocityTracker)
{
mVelocityTracker.Recycle();
mVelocityTracker = null;
}
break;
}
case MotionEventActions.Up: {
if (mIsDragging)
{
if (null != mVelocityTracker)
{
mLastTouchX = GetActiveX(ev);
mLastTouchY = GetActiveY(ev);
// Compute velocity within the last 1000ms
mVelocityTracker.AddMovement(ev);
mVelocityTracker.ComputeCurrentVelocity(1000);
float vX = mVelocityTracker.GetXVelocity(0), vY = mVelocityTracker
.GetYVelocity(0);
// If the velocity is greater than minVelocity, call
// listener
if (Math.Max(Math.Abs(vX), Math.Abs(vY)) >= mMinimumVelocity)
{
mListener.OnFling(mLastTouchX, mLastTouchY, -vX,
-vY);
}
}
}
// Recycle Velocity Tracker
if (null != mVelocityTracker)
{
mVelocityTracker.Recycle();
mVelocityTracker = null;
}
break;
}
}
return(true);
}
