Question

所以我正在开发基于文本的游戏，而且我遇到了一个在运行时没有正确填充对象的问题。我不完全确定为什么会这样，但这里是代码：

public class Area
{
    public List<Area> options;
    public string name;
    public string text;
    public uint time;

    private void loadOptions()
    {
        MainWindow.app.options.Children.Clear();
        for(int i = 0; i < options.Count(); i++)
        {
            Button b = new Button();

            b.Content = options[i].name;
            b.Name = "b"+i;
            b.Click += new RoutedEventHandler(optionClick);

            MainWindow.app.options.Children.Add(b);
        }
    }

    private void optionClick(object sender, EventArgs e)
    {
        Button clicked = (Button)sender;
        int index = Int32.Parse(clicked.Name.Split('b')[1]);
        options[index].load();
    }

    public void load()
    {
        loadOptions();
        MainWindow.app.mainText.SelectAll();
        MainWindow.app.mainText.Selection.Text = text;
    }
}

这是Area类的逻辑部分，我将所有其他区域保存在一个独立的文件中，在Areas类中，如下所示：

public static class Areas
{
    public static Area opening = new Area()
    {
        name = "Opening",
        text = "This is the first area, just a test for now, but will be fully filled out at a later time",
        time = 0,
        options = new List<Area>()
        {
            second
        }
    };

    public static Area second = new Area()
    {
        name = "second",
        text = "this is the second area for stuffs and stuffs",
        time = 0,
        options = new List<Area>()
        {
            opening
        }
    };
}

两者都是同一名称空间的一部分，但为了便于阅读，它们位于不同的文件中。我们的想法是，options数组包含玩家从该menue可以进入的所有可能菜单。第一个测试区域的代码是：

public Area test = new Area()
    {
        text = "This is yet another test to test stuffs and things and places",
        time = 0,
        options = new List<Area>
        {
            Areas.opening
        }
    };

并且正确加载，但是一旦我点击按钮，整个事情就会崩溃并抛出一个空引用异常。

以下是错误的详细信息：

    System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=LostWorlds
  StackTrace:
   at LostWorlds.Area.loadOptions() in C:\Users\Max\source\repos\LostWorlds\LostWorlds\LostWorlds\MainWindow.xaml.cs:line 356
   at LostWorlds.Area.load() in C:\Users\Max\source\repos\LostWorlds\LostWorlds\LostWorlds\MainWindow.xaml.cs:line 373
   at LostWorlds.Area.optionClick(Object sender, EventArgs e) in C:\Users\Max\source\repos\LostWorlds\LostWorlds\LostWorlds\MainWindow.xaml.cs:line 368
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
   at System.Windows.Controls.Primitives.ButtonBase.OnClick()
   at System.Windows.Controls.Button.OnClick()
   at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
   at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   at System.Windows.Application.RunDispatcher(Object ignore)
   at System.Windows.Application.RunInternal(Window window)
   at System.Windows.Application.Run(Window window)
   at System.Windows.Application.Run()
   at LostWorlds.App.Main()

从我收集的内容来看，使用静态类区域中的对象填充区域的选项列表存在一些问题，每当我查看列表的值时，它都有一个为空的条目。

Answer 1

我开始意识到这是Hoisting的一个问题，因为在“second”之前声明了“opening”引用了“second”，“opening”没有任何东西可以填充，因此返回了一个null引用。因此解决方案如下：

data.meals[0].name

还不完全确定如何使引用成为周期性的，但我相信我能弄明白。

C＃访问静态对象数组

1 个答案: