private static HorizontalLoopingSelectorItem GetFirstItem(HorizontalLoopingSelectorItem item, out int count)
{
count = 0;
while (item.Previous != null)
{
++count;
item = item.Previous;
}
return item;
}
private static HorizontalLoopingSelectorItem GetLastItem(HorizontalLoopingSelectorItem item, out int count)
{
count = 0;
while (item.Next != null)
{
++count;
item = item.Next;
}
return item;
}
private void SelectAndSnapTo(HorizontalLoopingSelectorItem item)
{
if (item == null)
{
return;
}
if (_selectedItem != null && _selectedItem != item)
{
_selectedItem.SetState(IsExpanded ? HorizontalLoopingSelectorItem.State.Expanded : HorizontalLoopingSelectorItem.State.Normal, true);
}
if (_selectedItem != item)
{
_selectedItem = item;
// Update DataSource.SelectedItem aynchronously so that animations have a chance to start.
Dispatcher.BeginInvoke(() =>
{
_isSelecting = true;
DataSource.SelectedItem = item.DataContext;
_isSelecting = false;
});
_selectedItem.SetState(HorizontalLoopingSelectorItem.State.Selected, true);
}
TranslateTransform transform = item.Transform;
if (transform != null)
{
double newPosition = -transform.X - Math.Round(item.ActualWidth / 2);
if (_panningTransform.X != newPosition)
{
AnimatePanel(_selectDuration, _selectEase, newPosition);
}
}
}
/// <summary>
/// Balances the items.
/// </summary>
private void Balance()
{
if (!IsReady)
{
return;
}
double actualItemWidth = ActualItemWidth;
double actualItemHeight = ActualItemHeight;
_additionalItemsCount = (int)Math.Round((ActualWidth * 1.5) / actualItemWidth);
HorizontalLoopingSelectorItem closestToMiddle = null;
int closestToMiddleIndex = -1;
if (_itemsPanel.Children.Count == 0)
{
// We need to get the selection and start from there
closestToMiddleIndex = 0;
_selectedItem = closestToMiddle = CreateAndAddItem(_itemsPanel, DataSource.SelectedItem);
closestToMiddle.Transform.X = -actualItemWidth / 2;
closestToMiddle.Transform.Y = (ActualHeight - actualItemHeight) / 2;
closestToMiddle.SetState(HorizontalLoopingSelectorItem.State.Selected, false);
}
else
{
closestToMiddleIndex = GetClosestItem();
closestToMiddle = (HorizontalLoopingSelectorItem)_itemsPanel.Children[closestToMiddleIndex];
}
int itemsBeforeCount;
HorizontalLoopingSelectorItem firstItem = GetFirstItem(closestToMiddle, out itemsBeforeCount);
int itemsAfterCount;
HorizontalLoopingSelectorItem lastItem = GetLastItem(closestToMiddle, out itemsAfterCount);
// Does the right side need items?
if (itemsBeforeCount < itemsAfterCount || itemsBeforeCount < _additionalItemsCount)
{
while (itemsBeforeCount < _additionalItemsCount)
{
object newData = DataSource.GetPrevious(firstItem.DataContext);
if (newData == null)
{
// There may be room to display more items, but there is no more data.
_maximumPanelScroll = -firstItem.Transform.X - actualItemWidth / 2;
if (_isAnimating && _panelAnimation.To.Value > _maximumPanelScroll)
{
Brake(_maximumPanelScroll);
}
break;
}
HorizontalLoopingSelectorItem newItem = null;
// Can an item from the left side be re-used?
if (itemsAfterCount > _additionalItemsCount)
{
newItem = lastItem;
lastItem = lastItem.Previous;
newItem.Remove();
newItem.Content = newItem.DataContext = newData;
}
else
{
// Make a new item
newItem = CreateAndAddItem(_itemsPanel, newData);
newItem.Transform.Y = (ActualHeight - actualItemHeight) / 2;
}
// Put the new item on the top
//if(newItem.Transform.X < firstItem.Transform.X)
newItem.Transform.X = firstItem.Transform.X - actualItemWidth;
newItem.InsertBefore(firstItem);
firstItem = newItem;
++itemsBeforeCount;
}
}
// Does the left side need items?
if (itemsAfterCount < itemsBeforeCount || itemsAfterCount < _additionalItemsCount)
{
while (itemsAfterCount < _additionalItemsCount)
{
object newData = DataSource.GetNext(lastItem.DataContext);
if (newData == null)
{
// There may be room to display more items, but there is no more data.
_minimumPanelScroll = -lastItem.Transform.X - actualItemWidth / 2;
if (_isAnimating && _panelAnimation.To.Value < _minimumPanelScroll)
{
Brake(_minimumPanelScroll);
}
break;
}
HorizontalLoopingSelectorItem newItem = null;
// Can an item from the top be re-used?
if (itemsBeforeCount > _additionalItemsCount)
{
newItem = firstItem;
firstItem = firstItem.Next;
newItem.Remove();
newItem.Content = newItem.DataContext = newData;
}
else
{
// Make a new item
newItem = CreateAndAddItem(_itemsPanel, newData);
newItem.Transform.Y = (ActualHeight - actualItemHeight) / 2;
}
// Put the new item on the bottom
newItem.Transform.X = lastItem.Transform.X + actualItemWidth;
newItem.InsertAfter(lastItem);
lastItem = newItem;
++itemsAfterCount;
}
}
_temporaryItemsPool = null;
}
void listener_DragStarted(object sender, DragStartedGestureEventArgs e)
{
//Debug.WriteLine("listener_DragStarted");
if (e.Direction == Orientation.Horizontal)
{
_state = State.Dragging;
e.Handled = true;
_selectedItem = null;
if (!IsExpanded)
{
IsExpanded = true;
}
_dragTarget = _panningTransform.X;
UpdateItemState();
}
}
void listener_Flick(object sender, FlickGestureEventArgs e)
{
//Debug.WriteLine("listener_Flick");
if (e.Direction == Orientation.Horizontal)
{
_state = State.Flicking;
_selectedItem = null;
if (!IsExpanded)
{
IsExpanded = true;
}
Point velocity = new Point(e.HorizontalVelocity, 0);
double flickDuration = PhysicsConstants.GetStopTime(velocity);
Point flickEndPoint = PhysicsConstants.GetStopPoint(velocity);
IEasingFunction flickEase = PhysicsConstants.GetEasingFunction(flickDuration);
AnimatePanel(new Duration(TimeSpan.FromSeconds(flickDuration)), flickEase, _panningTransform.X + flickEndPoint.X);
e.Handled = true;
_selectedItem = null;
UpdateItemState();
}
}
internal void InsertBefore(HorizontalLoopingSelectorItem before)
{
Next = before;
Previous = before.Previous;
if (before.Previous != null)
{
before.Previous.Next = this;
}
before.Previous = this;
}
internal void InsertAfter(HorizontalLoopingSelectorItem after)
{
Next = after.Next;
Previous = after;
if (after.Next != null)
{
after.Next.Previous = this;
}
after.Next = this;
}
internal void Remove()
{
if (Previous != null)
{
Previous.Next = Next;
}
if (Next != null)
{
Next.Previous = Previous;
}
Next = Previous = null;
}
private void OnManipulationCompleted(object sender, ManipulationCompletedEventArgs e)
{
if (_isDragging)
{
// See if it was a flick
if (e.IsInertial)
{
_state = State.Flicking;
_selectedItem = null;
if (!IsExpanded)
{
IsExpanded = true;
}
Point velocity = new Point(e.FinalVelocities.LinearVelocity.X, 0);
double flickDuration = PhysicsConstants.GetStopTime(velocity);
Point flickEndPoint = PhysicsConstants.GetStopPoint(velocity);
IEasingFunction flickEase = PhysicsConstants.GetEasingFunction(flickDuration);
AnimatePanel(new Duration(TimeSpan.FromSeconds(flickDuration)), flickEase, _panningTransform.X + flickEndPoint.X);
e.Handled = true;
_selectedItem = null;
UpdateItemState();
}
if (_state == State.Dragging)
{
SelectAndSnapToClosest();
}
_state = State.Expanded;
}
}
private void OnManipulationDelta(object sender, ManipulationDeltaEventArgs e)
{
if (_isDragging)
{
AnimatePanel(_panDuration, _panEase, _dragTarget += e.DeltaManipulation.Translation.X);
e.Handled = true;
}
else if (Math.Abs(e.CumulativeManipulation.Translation.Y) > DragSensitivity)
{
_isAllowedToDragHorizontally = false;
}
else if (_isAllowedToDragHorizontally && Math.Abs(e.CumulativeManipulation.Translation.X) > DragSensitivity)
{
_isDragging = true;
_state = State.Dragging;
e.Handled = true;
_selectedItem = null;
if (!IsExpanded)
{
IsExpanded = true;
}
_dragTarget = _panningTransform.X;
UpdateItemState();
}
}