WPF bing地圖控制首先添加到集合的多義線/多邊形

Question

我正在處理這個表面項目，我們有一個bing地圖控件，並且我們想通過使用數據綁定在地圖上繪製多段線。

發生的奇怪行爲是當我點擊添加按鈕時，地圖上沒有任何反應。如果我稍微移動地圖，多段線就會繪製在地圖上。這種類型的另一種場景是單擊添加按鈕一次，沒有任何反應，再次單擊它就會繪製兩條折線。 （在我的手動集合中，我有4個LocationCollections），所以第三次單擊和第四次單擊都會發生同樣的情況，即再次繪製兩條線。

我完全不知道在哪裏再來解決這個問題。我嘗試訂閱Layoutupdated事件，這兩種情況都會發生。還將一個collectionchanged事件添加到observablecollection，以查看添加是否被觸發，並且是否觸發。我嘗試的另一件事是將折線更改爲圖釘，並從pipelineviewmodel中的位置集合中獲取第一個位置，而不是預期的工作。

我已經上傳sample project如果你想看看自己在發生什麼事情。

真的希望有人能指引我走向正確的方向，因爲我再也沒有線索了。

下面你可以看到我寫的代碼：

我有以下的ViewModels：

MainViewModel

public class MainViewModel 
{ 
    private ObservableCollection<PipelineViewModel> _pipelines; 

    public ObservableCollection<PipelineViewModel> Pipes 
    { 
     get { return _pipelines; } 
    } 

    public MainViewModel() 
    { 
     _pipelines = new ObservableCollection<PipelineViewModel>(); 
    } 
} 

而且PipelineViewModel其中有位置的集合，其實現INotifyPropertyChanged ：

Pipelin eViewModel

public class PipelineViewModel : ViewModelBase 
{ 
    private LocationCollection _locations; 

    public string Geometry { get; set; } 
    public string Label { get; set; } 
    public LocationCollection Locations 
    { 
     get { return _locations; } 
     set 
     { 
      _locations = value; 
      RaisePropertyChanged("Locations"); 
     } 
    } 
} 

我的XAML看起來像如下：

<s:SurfaceWindow x:Class="SurfaceApplication3.SurfaceWindow1" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:s="http://schemas.microsoft.com/surface/2008" 
    xmlns:m="clr-namespace:Microsoft.Maps.MapControl.WPF;assembly=Microsoft.Maps.MapControl.WPF" 
    Title="SurfaceApplication3"> 
    <s:SurfaceWindow.Resources> 
     <DataTemplate x:Key="Poly"> 
      <m:MapPolyline Locations="{Binding Locations}" Stroke="Black" StrokeThickness="5" /> 
     </DataTemplate> 
    </s:SurfaceWindow.Resources> 
    <Grid> 
     <m:Map ZoomLevel="8" Center="52.332074,5.542302" Name="Map"> 
      <m:MapItemsControl Name="x" ItemsSource="{Binding Pipes}" ItemTemplate="{StaticResource Poly}" /> 
     </m:Map> 
     <Button Name="add" Width="100" Height="50" Content="Add" Click="add_Click"></Button> 
    </Grid> 
</s:SurfaceWindow> 

而在我們的代碼隱藏我們正在建立綁定像這樣的單擊事件：

private int _counter = 0; 
private string[] geoLines; 

private MainViewModel _mainViewModel = new MainViewModel(); 

/// <summary> 
/// Default constructor. 
/// </summary> 
public SurfaceWindow1() 
{ 
    InitializeComponent(); 

    // Add handlers for window availability events 
    AddWindowAvailabilityHandlers(); 

    this.DataContext = _mainViewModel; 

    geoLines = new string[4]{ "52.588032,5.979309; 52.491143,6.020508; 52.397391,5.929871; 52.269838,5.957336; 52.224435,5.696411; 52.071065,5.740356", 
           "52.539614,4.902649; 52.429222,4.801025; 52.308479,4.86145; 52.246301,4.669189; 52.217704,4.836731; 52.313516,5.048218", 
           "51.840869,4.394531; 51.8731,4.866943; 51.99841,5.122375; 52.178985,5.438232; 51.8731,5.701904; 52.071065,6.421509", 
           "51.633362,4.111633; 51.923943,6.193542; 52.561325,5.28717; 52.561325,6.25946; 51.524125,5.427246; 51.937492,5.28717" }; 
} 

private void add_Click(object sender, RoutedEventArgs e) 
{ 
    PipelineViewModel plv = new PipelineViewModel(); 
    plv.Locations = AddLinestring(geoLines[_counter]); 
    plv.Geometry = geoLines[_counter]; 

    _mainViewModel.Pipes.Add(plv); 

    _counter++; 
} 

private LocationCollection AddLinestring(string shapegeo) 
{ 
    LocationCollection shapeCollection = new LocationCollection(); 

    string[] lines = Regex.Split(shapegeo, ";"); 
    foreach (string line in lines) 
    { 
     string[] pts = Regex.Split(line, ","); 

     double lon = double.Parse(pts[1], new CultureInfo("en-GB")); 
     double lat = double.Parse(pts[0], new CultureInfo("en-GB")); 
     shapeCollection.Add(new Location(lat, lon)); 
    } 

    return shapeCollection; 
} 

Answer 1

我做了一些挖掘在這個問題上，發現在Map實現中有一個錯誤。我也提出了這一個解決方法，可以這樣

<m:Map ...> 
    <m:MapItemsControl Name="x" 
         behaviors:MapFixBehavior.FixUpdate="True"/> 
</m:Map> 

我包括在此修復程序示例應用程序中使用，並在這裏上傳吧：SurfaceApplication3.zip

---

每個ContentPresenter視覺樹是這個樣子

當您添加新的項目到集合中的Polygon得到日最初錯誤的是Points。而不是像59, 29這樣的值，它會得到像0.0009, 0.00044。

的點在MeasureOverride計算在MapShapeBase並做計算的部分看起來像這樣

MapMath.TryLocationToViewportPoint(ref this._NormalizedMercatorToViewport, location, out point2); 

最初，_NormalizedMercatorToViewport將其默認值（一切都被設置爲0）這樣的計算雲都是錯的。 _NormalizedMercatorToViewport在方法SetView中設置，該方法從MeasureOverride中調用MapLayer。

MeasureOverride in MapLayer有以下兩條if語句。

if ((element is ContentPresenter) && (VisualTreeHelper.GetChildrenCount(element) > 0)) 
{ 
    child.SetView(...) 
} 

這出來作爲false因爲ContentPresenter並沒有一個直觀的孩子呢，還是產生了。 這是問題。

第二個看起來像這樣

IProjectable projectable2 = element as IProjectable; 
if (projectable2 != null) 
{ 
    projectable2.SetView(...); 
} 

這爲false出來也因爲元素，這是一個ContentPresenter，沒有實現IProjectable。這由孩子MapShapeBase執行，再一次，這個孩子尚未產生。

所以，SetView不會被調用，並在_NormalizedMercatorToViewport將MapShapeBase有其默認值，並計算出了問題，當你添加新項目的第一次。

---

解決方法

要解決這個問題，我們需要強制MapLayer的重新測量。當新的ContentPresenter被添加到MapItemsControl但在ContentPresenter有一個可視孩子之後，必須完成此操作。給力的更新

一種方法是創建具有元數據標記AffectsRender，AffectsArrange和AffectsMeasure設置爲true的附加屬性。然後，只要我們想要更新，我們只需更改此屬性的值。

這是一個附加的行爲，這樣做。使用這樣的

<m:Map ...> 
    <m:MapItemsControl Name="x" 
         behaviors:MapFixBehavior.FixUpdate="True"/> 
</m:Map> 

MapFixBehavior

public class MapFixBehavior 
{ 
    public static DependencyProperty FixUpdateProperty = 
     DependencyProperty.RegisterAttached("FixUpdate", 
              typeof(bool), 
              typeof(MapFixBehavior), 
              new FrameworkPropertyMetadata(false, 
                      OnFixUpdateChanged)); 

    public static bool GetFixUpdate(DependencyObject mapItemsControl) 
    { 
     return (bool)mapItemsControl.GetValue(FixUpdateProperty); 
    } 
    public static void SetFixUpdate(DependencyObject mapItemsControl, bool value) 
    { 
     mapItemsControl.SetValue(FixUpdateProperty, value); 
    } 

    private static void OnFixUpdateChanged(DependencyObject target, DependencyPropertyChangedEventArgs e) 
    { 
     MapItemsControl mapItemsControl = target as MapItemsControl; 
     ItemsChangedEventHandler itemsChangedEventHandler = null; 
     itemsChangedEventHandler = (object sender, ItemsChangedEventArgs ea) => 
     { 
      if (ea.Action == NotifyCollectionChangedAction.Add) 
      { 
       EventHandler statusChanged = null; 
       statusChanged = new EventHandler(delegate 
       { 
        if (mapItemsControl.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated) 
        { 
         mapItemsControl.ItemContainerGenerator.StatusChanged -= statusChanged; 
         int index = ea.Position.Index + ea.Position.Offset; 
         ContentPresenter contentPresenter = 
          mapItemsControl.ItemContainerGenerator.ContainerFromIndex(index) as ContentPresenter; 
         if (VisualTreeHelper.GetChildrenCount(contentPresenter) == 1) 
         { 
          MapLayer mapLayer = GetVisualParent<MapLayer>(mapItemsControl); 
          mapLayer.ForceMeasure(); 
         } 
         else 
         { 
          EventHandler layoutUpdated = null; 
          layoutUpdated = new EventHandler(delegate 
          { 
           if (VisualTreeHelper.GetChildrenCount(contentPresenter) == 1) 
           { 
            contentPresenter.LayoutUpdated -= layoutUpdated; 
            MapLayer mapLayer = GetVisualParent<MapLayer>(mapItemsControl); 
            mapLayer.ForceMeasure(); 
           } 
          }); 
          contentPresenter.LayoutUpdated += layoutUpdated; 
         } 
        } 
       }); 
       mapItemsControl.ItemContainerGenerator.StatusChanged += statusChanged; 
      } 
     }; 
     mapItemsControl.ItemContainerGenerator.ItemsChanged += itemsChangedEventHandler; 
    } 

    private static T GetVisualParent<T>(object childObject) where T : Visual 
    { 
     DependencyObject child = childObject as DependencyObject; 
     while ((child != null) && !(child is T)) 
     { 
      child = VisualTreeHelper.GetParent(child); 
     } 
     return child as T; 
    } 
} 

MapLayerExtensions

public static class MapLayerExtensions 
{ 
    private static DependencyProperty ForceMeasureProperty = 
     DependencyProperty.RegisterAttached("ForceMeasure", 
              typeof(int), 
              typeof(MapLayerExtensions), 
              new FrameworkPropertyMetadata(0, 
               FrameworkPropertyMetadataOptions.AffectsRender | 
               FrameworkPropertyMetadataOptions.AffectsArrange | 
               FrameworkPropertyMetadataOptions.AffectsMeasure)); 

    private static int GetForceMeasure(DependencyObject mapLayer) 
    { 
     return (int)mapLayer.GetValue(ForceMeasureProperty); 
    } 
    private static void SetForceMeasure(DependencyObject mapLayer, int value) 
    { 
     mapLayer.SetValue(ForceMeasureProperty, value); 
    } 

    public static void ForceMeasure(this MapLayer mapLayer) 
    { 
     SetForceMeasure(mapLayer, GetForceMeasure(mapLayer) + 1); 
    } 
}