windowsphone瀑布流&ui虚拟化

// 自定义一个 字典 ，用来保存每项的 Y坐标 和它 本身 的引用
Dictionary double, Border dic = new Dictionary double, Border
public PowerListBox()
{
DefaultStyleKey = typeof(PowerListBox);
Loaded += PowerListBox_Loaded;
Unloaded += PowerListBox_Unloaded;
}
private ScrollViewer _scrollView;
private bool _isScrolling;
void PowerListBox_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
if (DesignerProperties.GetIsInDesignMode(this))
return;
ApplyTemplate();
_scrollView.ScrollToVerticalOffset(_scrollView.VerticalOffset);
var border = _scrollView.Descendants Border ().FirstOrDefault();
Debug.Assert(border != null);
var vsGroup = VisualStateManager.GetVisualStateGroups(border).OfType VisualStateGroup ().FirstOrDefault(s = s.Name == "ScrollStates");
Debug.Assert(vsGroup != null);
vsGroup.CurrentStateChanging += vsGroup_CurrentStateChanging;
if (ItemsRootPanel != null ItemsRootPanel.Children != null)
{
double height_sum=;
dic.Clear();
for (int i = ; i ItemsRootPanel.Children.Count; i++)
{
// 因为 ListBox 是通过数据绑定生成的列表，所以需要通过 ItemContainerGenerator 获得
// 每一项的 StackPanel 这个父控件
Border fe = VisualTreeHelper.GetChild(ItemsRootPanel.Children[i], ) as Border;
dic.Add(height_sum, fe);
// 累加 Y高度
//var height = .GetItemHeight(i);
if (height_sum = (ItemsRootPanel as WaterFallPanel).GetItemHeight(i))
{
height_sum = (ItemsRootPanel as WaterFallPanel).GetItemHeight(i) + ;
}
else
{
height_sum = (ItemsRootPanel as WaterFallPanel).GetItemHeight(i);
// 设置它的高度为自己的实际高度
fe.Height = fe.ActualHeight;
}
void PowerListBox_Unloaded(object sender, System.Windows.RoutedEventArgs e)
{
var border = _scrollView.Descendants Border ().FirstOrDefault();
Debug.Assert(border != null);
var vsGroup = VisualStateManager.GetVisualStateGroups(border).OfType VisualStateGroup ().FirstOrDefault(s = s.Name == "ScrollStates");
Debug.Assert(vsGroup != null);
vsGroup.CurrentStateChanging -= vsGroup_CurrentStateChanging;
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
_scrollView = GetTemplateChild("ScrollViewer") as ScrollViewer;
Debug.Assert(_scrollView != null);
void vsGroup_CurrentStateChanging(object sender, VisualStateChangedEventArgs e)
{
if (e.NewState.Name == "NotScrolling")
{
_isScrolling = false;
CompositionTarget.Rendering -= CompositionTarget_Rendering;
}
else
{
_isScrolling = true;
CompositionTarget.Rendering += CompositionTarget_Rendering;
}
}
void CompositionTarget_Rendering(object sender, EventArgs e)
{
RefreshDisplayArea();
void RefreshDisplayArea()
{
foreach (var keyValue in dic)
{
if (((_scrollView.VerticalOffset - ) keyValue.Key || keyValue.Key (_scrollView.VerticalOffset + )))
{
keyValue.Value.Child.Visibility = Visibility.Collapsed;
}
else
{
keyValue.Value.Child.Visibility = Visibility.Visible;
}
}
//for (int i = 0; i ItemsRootPanel.Children.Count; i++)
//{
// var item = GetItem(i);
// var height = (ItemsRootPanel as WaterFallPanel).GetItemHeight(i) ;
// if (((_scrollView.VerticalOffset - 20) height || height (_scrollView.VerticalOffset + 607)))
// {
// FrameworkElement fe = VisualTreeHelper.GetChild(item, 0) as FrameworkElement;
// fe.Visibility = Visibility.Collapsed;
// //keyValue.Value.Children[0].Visibility = System.Windows.Visibility.Collapsed;
// //keyValue.Value.Children[1].Visibility = System.Windows.Visibility.Collapsed;
// }
// else
// {
// FrameworkElement fe = VisualTreeHelper.GetChild(item, 0) as FrameworkElement;
// fe.Visibility = Visibility.Visible;
// //keyValue.Value.Children[0].Visibility = System.Windows.Visibility.Visible;
// //keyValue.Value.Children[1].Visibility = System.Windows.Visibility.Visible;
// }
private ListBoxItem GetItem(int index)
{
if (index || index = Items.Count)
return null;
if (ItemsSource != null)
{
var isVirtualizing = VirtualizingStackPanel.GetIsVirtualizing(this);
if (!isVirtualizing)
{
Debug.Assert(ItemsRootPanel != null);
return ItemsRootPanel.Children[index] as ListBoxItem;
}
Debug.Assert(ItemContainerGenerator != null);
return ItemContainerGenerator.ContainerFromIndex(index) as ListBoxItem;
}
return Items[index] as ListBoxItem;
#region FirstVisibleIndex
public static readonly DependencyProperty FirstVisibleIndexProperty =
DependencyProperty.Register("FirstVisibleIndex", typeof(int), typeof(PowerListBox), new PropertyMetadata());
public int FirstVisibleIndex
{
get { return (int)GetValue(FirstVisibleIndexProperty); }
private set { SetValue(FirstVisibleIndexProperty, value); }
}
#endregion
#region LastVisibleIndex
public static readonly DependencyProperty LastVisibleIndexProperty =
DependencyProperty.Register("LastVisibleIndex", typeof(int), typeof(PowerListBox), new PropertyMetadata());
public int LastVisibleIndex
{
get { return (int)GetValue(LastVisibleIndexProperty); }
private set { SetValue(LastVisibleIndexProperty, value); }
}
#endregion
private Panel _itemsRootPanel;
private Panel ItemsRootPanel
{
get
{
if (_itemsRootPanel == null ItemsPresenter != null)
{
_itemsRootPanel = ItemsPresenter.ChildrenEx().FirstOrDefault() as Panel;
}
return _itemsRootPanel;
}
private ItemsPresenter _itemsPresenter;
private ItemsPresenter ItemsPresenter
{
get { return _itemsPresenter ?? (_itemsPresenter = _scrollView.Descendants ItemsPresenter ().FirstOrDefault()); }
}