在win8中如何实现下拉刷新的功能

淡淡回忆

　　现在我以listview为例来讲述下拉刷新的功能！
　　在xaml中设置listview一定要设置一个这样的属性，IsSwipeEnabled=false,然后再listview控件的前面要布局下拉刷新的图标及提示,在listview控件的后面也要布局上拉时的提示信息。
　　现在我将个人的布局展现出来，仅供大家参考！











































　　
　　
　　然后在后台就要实现下拉刷新的正真效果呢!
　　这里特别要指出的要注册这样一个事件,  this.LayoutUpdated += ForumList_LayoutUpdated;不然就实现不了!
　　也要注册listview的触摸事件，例如：
　　this.ForumList.ManipulationStarted+=ForumList_ManipulationStarted;
            this.ForumList.ManipulationDelta+=ForumList_ManipulationDelta;
            this.ForumList.ManipulationCompleted+=ForumList_ManipulationCompleted;
　　
　　思路就是这样的,现在我就讲后台的逻辑也给大家参考!



  DispatcherTimer toptimer = new DispatcherTimer();
DispatcherTimer timer = new DispatcherTimer();
private ScrollViewer listViewScrollViewer;
private double listviewItemHeight = -1;
private int optLimitHeight = 96;
private bool isInPrpcessing = false;
private Point eventStartPoint;
private double lastDeltaHandledY = 0;
private ObservableCollection listDataItems = new ObservableCollection();
//移动开始位置
private Point moveStartPoint;
//是否可以移动
private bool canMove = false;
public ListPage()
{
this.InitializeComponent();
this.imgArrow.Source = new BitmapImage(new Uri(@"ms-appx:///Assets/pullrefresh_arrow.png",UriKind.RelativeOrAbsolute));
this.LayoutUpdated += ForumList_LayoutUpdated;
this.recRefresh.SizeChanged+=recRefresh_SizeChanged;
this.ForumList.ManipulationStarted+=ForumList_ManipulationStarted;
this.ForumList.ManipulationDelta+=ForumList_ManipulationDelta;
this.ForumList.ManipulationCompleted+=ForumList_ManipulationCompleted;
//this.ForumList.SelectionChanged+=ForumList_SelectionChanged;
}
　　




  private void ForumList_LayoutUpdated(object sender, object e)
{
if (this.Height.Equals(double.NaN) && this.Parent != null)
{
this.Height = ((Windows.UI.Xaml.FrameworkElement)(this.Parent)).ActualHeight;
}
if (listViewScrollViewer == null)
{
listViewScrollViewer = FindVisualElement(VisualTreeHelper.GetParent(this));
listViewScrollViewer.ManipulationMode = ManipulationModes.All;
}
for (int i = 0; i < this.ForumList.Items.Count; i++)
{
ListViewItem item = this.ForumList.ItemContainerGenerator.ContainerFromIndex(i) as ListViewItem;
if (item != null && item.ManipulationMode != ManipulationModes.All)
{
item.ManipulationMode = ManipulationModes.All;
if (listviewItemHeight < 0)
{
listviewItemHeight = ((Windows.UI.Xaml.FrameworkElement)(item)).ActualHeight;
}
}
}
}
private static T FindVisualElement(DependencyObject container) where T : DependencyObject
{
Queue childQueue = new Queue();
childQueue.Enqueue(container);
while (childQueue.Count > 0)
{
DependencyObject current = childQueue.Dequeue();
T result = current as T;
if (result != null && result != container)
{
return result;
}
int childCount = VisualTreeHelper.GetChildrenCount(current);
for (int childIndex = 0; childIndex < childCount; childIndex++)
{
childQueue.Enqueue(VisualTreeHelper.GetChild(current, childIndex));
}
}
return null;
}
　　



private void recRefresh_SizeChanged( object sender,SizeChangedEventArgs e)
{
if (e.NewSize.Height > this.optLimitHeight && !isInPrpcessing)
{
if (!this.txtOperationTip.Text.Equals("松开刷新…"))
{
this.txtOperationTip.Text = "松开刷新…";
this.ImgStoryBoard.Begin();
}
}
}
private void ForumList_ManipulationStarted(object sender, ManipulationStartedRoutedEventArgs e)
{
eventStartPoint = e.Position;
lastDeltaHandledY = 0;
if (!isInPrpcessing)
{
this.txtOperationTip.Text = "下拉刷新列表…";
}
e.Handled = true;
}
private void ForumList_ManipulationDelta(object sender,ManipulationDeltaRoutedEventArgs e)
{
double offset = e.Cumulative.Translation.Y - lastDeltaHandledY;
if (listViewScrollViewer.VerticalOffset < 3)
{
double height = recRefresh.Height + offset;
recRefresh.Height = height > 0 ? height : 0;
if (offset < 0 && recRefresh.Height = listViewScrollViewer.ScrollableHeight - 1)
{
double height = recLoad.Height - offset;
recLoad.Height = height > 0 ? height : 0;
if (offset > 0 && recLoad.Height  0)
{
if (recRefresh.Height > optLimitHeight && this.Refreshable)
{
recRefresh.Height = 96;
imgArrow.Visibility = Visibility.Collapsed;
prgRefresh.Visibility = Visibility.Visible;
if (!this.isInPrpcessing)
{
System.Diagnostics.Debug.WriteLine(this.isInPrpcessing);
DoListDataSourceRefresh();
}
}
else
{
recRefresh.Height = 0;
}
listViewScrollViewer.ScrollToVerticalOffset(2.05);
}
if (recLoad.Height > 0)
{
if (recLoad.Height > optLimitHeight)
{
recLoad.Height = 68;
splNextPageLoading.Visibility = Visibility.Visible;
if (!this.isInPrpcessing)
{
DoListDataLoadNextPage();
}
}
else
{
recLoad.Height = 0;
}
}
}
private  void DoListDataSourceRefresh()
{
this.isInPrpcessing = true;
this.txtOperationTip.Text = "加载数据中";
this.isInPrpcessing = false;
this.recRefresh.Height = 0;
this.imgArrow.Visibility = Windows.UI.Xaml.Visibility.Visible;
this.prgRefresh.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
this.ImgStoryBoard.Begin(); //箭头复位
}
private  void DoListDataLoadNextPage()
{
this.recLoad.Height = 0;
splNextPageLoading.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
}
public event SelectionChangedEventHandler SelectionChanged;
private void ForumList_SelectionChanged( object sender,SelectionChangedEventArgs e)
{
SelectionChanged(sender,e);
}