Draggable Boxview Absturz Fehler Xamarin

Question

Das Problem liegt mit der ziehbaren Ansicht, im ersten Teil des Codes lokal: Draggableview, stürzt das Programm am Xaml Teil des Codes, aber ich kann nicht herausfinden, was das Problem ist. Ich habe die ziehbare Ansicht entfernt und versucht, Haltepunkte im nicht-xaml-Teil des Codes auszugeben, aber ich kann nicht herausfinden, was ein Problem verursacht.

<ContentPage> 
    <ContentPage.Padding> 
     <OnPlatform x:TypeArguments="Thickness"> 
      <On Platform="iOS, Android" Value="0,40,0,0" /> 
     </OnPlatform> 
    </ContentPage.Padding> 
    <Grid BackgroundColor="White" ColumnSpacing="10" RowSpacing="10"> 
     <Label Text="Red" FontSize="Medium" HorizontalOptions="Center" /> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
      <RowDefinition Height="*" /> 
     </Grid.RowDefinitions> 

     <Grid.ColumnDefinitions> 
      <ColumnDefinition Width="*" /> 
      <ColumnDefinition Width="*" /> 
      <ColumnDefinition Width="*" /> 
     </Grid.ColumnDefinitions> 

     <BoxView Color="Black" Grid.Column="1" Grid.RowSpan="1"/> 
     <BoxView Color="Gray" Grid.Column="2" Grid.RowSpan="1"/> 
     <Label Text="9" Font ="60" Grid.Row="1" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="8" Font ="60" Grid.Row="2" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="7" Font ="60" Grid.Row="3" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="6" Font ="60" Grid.Row="4" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="5" Font ="60" Grid.Row="5" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="4" Font ="60" Grid.Row="6" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="3" Font ="60" Grid.Row="7" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="2" Font ="60" Grid.Row="8" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="1" Font ="60" Grid.Row="9" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 
     <Label Text="0" Font ="60" Grid.Row="10" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" TextColor="Black" /> 

     <local:DraggableView x:Name="dragView" DragMode="LongPress" DragDirection="All" > 
      <local:DraggableView.Content> 
       <BoxView x:Name="image" ItemSelected="Handle_ItemSelected" /> 
      </local:DraggableView.Content> 
     </local:DraggableView> 
    </Grid> 

</ContentPage> 

Helfer

public enum DragDirectionType 
{ 
    All, 
    Vertical, 
    Horizontal 
} 
public enum DragMode 
{ 
    Touch, 
    LongPress 
} 

DraggableView

public partial class DraggableView : ContentView 
    { 
     public event EventHandler DragStart = delegate { }; 
     public event EventHandler DragEnd = delegate { }; 

     public static readonly BindableProperty DragDirectionProperty = BindableProperty.Create(
      propertyName: "DragDirection", 
      returnType: typeof(DragDirectionType), 
      declaringType: typeof(DraggableView), 
      defaultValue: DragDirectionType.All, 
      defaultBindingMode: BindingMode.TwoWay); 

     public DragDirectionType DragDirection 
     { 
      get { return (DragDirectionType)GetValue(DragDirectionProperty); } 
      set { SetValue(DragDirectionProperty, value); } 
     } 


     public static readonly BindableProperty DragModeProperty = BindableProperty.Create(
      propertyName: "DragMode", 
      returnType: typeof(DragMode), 
      declaringType: typeof(DraggableView), 
      defaultValue: DragMode.LongPress, 
      defaultBindingMode: BindingMode.TwoWay); 

     public DragMode DragMode 
     { 
      get { return (DragMode)GetValue(DragModeProperty); } 
      set { SetValue(DragModeProperty, value); } 
     } 

     public static readonly BindableProperty IsDraggingProperty = BindableProperty.Create(
      propertyName: "IsDragging", 
      returnType: typeof(bool), 
      declaringType: typeof(DraggableView), 
      defaultValue: false, 
      defaultBindingMode: BindingMode.TwoWay); 

     public bool IsDragging 
     { 
      get { return (bool)GetValue(IsDraggingProperty); } 
      set { SetValue(IsDraggingProperty, value); } 
     } 


     public void DragStarted() 
     { 
      DragStart(this, default(EventArgs)); 
      IsDragging = true; 
     } 

     public void DragEnded() 
     { 
      IsDragging = false; 
      DragEnd(this, default(EventArgs)); 
     } 

    } 
} 

Dies ist der Android-Teil des Codes

[assembly: ExportRenderer(typeof(DraggableView), typeof(DraggableViewRenderer))] 

namespace BabakusXamarin.Droid 
{ 
    public class DraggableViewRenderer : VisualElementRenderer<Xamarin.Forms.View> 
    { 
     float originalX; 
     float originalY; 
     float dX; 
     float dY; 
     bool firstTime = true; 
     bool touchedDown = false; 

     protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.View> e) 
     { 
      base.OnElementChanged(e); 


      if (e.OldElement != null) 
      { 
       LongClick -= HandleLongClick; 
      } 
     } 

     private void HandleLongClick(object sender, LongClickEventArgs e) 
     { 
      var dragView = Element as DraggableView; 
      if (firstTime) 
      { 
       originalX = GetX(); 
       originalY = GetY(); 
       firstTime = false; 
      } 
      dragView.DragStarted(); 
      touchedDown = true; 
     } 

     protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) 
     { 
      var dragView = Element as DraggableView; 
      base.OnElementPropertyChanged(sender, e); 

     } 
     protected override void OnVisibilityChanged(AView.View changedView, [GeneratedEnum] ViewStates visibility) 
     { 
      base.OnVisibilityChanged(changedView, visibility); 
      if (visibility == ViewStates.Visible) 
      { 



      } 
     } 
     public override bool OnTouchEvent(MotionEvent e) 
     { 
      float x = e.RawX; 
      float y = e.RawY; 
      var dragView = Element as DraggableView; 
      switch (e.Action) 
      { 
       case MotionEventActions.Down: 
        if (dragView.DragMode == DragMode.Touch) 
        { 
         if (!touchedDown) 
         { 
          if (firstTime) 
          { 
           originalX = GetX(); 
           originalY = GetY(); 
           firstTime = false; 
          } 
          dragView.DragStarted(); 
         } 

         touchedDown = true; 
        } 
        dX = x - this.GetX(); 
        dY = y - this.GetY(); 
        break; 
       case MotionEventActions.Move: 
        if (touchedDown) 
        { 
         if (dragView.DragDirection == DragDirectionType.All || dragView.DragDirection == DragDirectionType.Horizontal) 
         { 
          SetX(x - dX); 
         } 

         if (dragView.DragDirection == DragDirectionType.All || dragView.DragDirection == DragDirectionType.Vertical) 
         { 
          SetY(y - dY); 
         } 

        } 
        break; 
       case MotionEventActions.Up: 
        touchedDown = false; 
        dragView.DragEnded(); 
        break; 
       case MotionEventActions.Cancel: 
        touchedDown = false; 
        break; 
      } 
      return base.OnTouchEvent(e); 
     } 

     public override bool OnInterceptTouchEvent(MotionEvent e) 
     { 

      BringToFront(); 
      return true; 
     } 

    } 


} 

Answer 1

Das Problem mit der legt ziehbare Ansicht, im ersten Teil des Codes lokal: draggableview, stürzt das Programm am Xaml Teil des Codes, aber ich kann nicht herausfinden, was das Problem ist.

Das Problem ist: Es gibt keine ItemSelected in BoxView. Durch das Entfernen von ItemSelected="ItemSelected" funktionieren Ihre XAML-Codes.

Einzelheiten zu BoxView finden Sie unter BoxView.