Question

namespace FBLALibraryApp2
{
public partial class GenrePage : ContentPage
{

    public GenrePage()
    {
        InitializeComponent();
        listView.ItemsSource = DataStorage.GenreList;
    }

    private void SearchBar_TextChanged(object sender, TextChangedEventArgs e)
    {

    }

    private void listView_ItemSelected(object sender, SelectedItemChangedEventArgs e)
    {
        listView.SelectedItem = null;
    }

    async private void listView_ItemTapped(object sender, ItemTappedEventArgs e)
    {
        if (e.Item is GenreGroup)
            await Navigation.PushAsync(new GenreView((GenreGroup)e.Item));
    }
    }
}

以下是我在Xamarin中制作的页面的代码。这是一个显示GenreGroup列表的简单页面。它在过去运行良好，但最近，当我更改我的代码初始化列表时，应用程序将运行到一个空白屏幕。所以，我暂停了调试，看到它最终被卡在了，listView.ItemSource = DataStorage.GenreList;。在按下继续时，应用程序将抛出TypeInitializationException。我担心也许我的代码的最新版本没有被构建（这在我之前启用了快速部署时发生了），所以我添加了一个Debug.log（＆＃34; x＆＃34;）;在麻烦的行之前确保最新的代码正在运行。执行此操作后，应用程序开始冻结InitializeComponent（）并抛出相同的异常。我在这里难以理解该做什么。这是我声明列表的代码：

public static class DataStorage
{
    public static List<Book> AllBookList = new List<Book> { new Book { Title = "Harry Potter", Author = "J.K. Rowling", Summary="lorem ipsum dolorum sdjfa;dklfja;dkfj;akdfja;dfjkaf", Genre= new string[] { "Fantasy", "Adventure" }, pubYear="2017" }, new Book { Title = "The Hunger Games", Author = "Suzanne Collins", Summary = "lorem ipsum dolorum sdjfa;dklfja;dkfj;akdfja;dfjkaf", Genre = new string[] { "Sci-Fi" }, pubYear = "2017" }, new Book { Title = "Thief in the Night", Author = "Jack Nimble", Summary = "lorem ipsum dolorum sdjfa;dklfja;dkfj;akdfja;dfjkaf", Genre = new string[] { "Mystery"}, pubYear = "2017" }, new Book { Title = "Hardy Bros.", Author = "Johnny Heather", Summary = "lorem ipsum dolorum sdjfa;dklfja;dkfj;akdfja;dfjkaf", Genre = new string[] { "Mystery", "Comedy" }, pubYear = "2017" } };
    public static List<GenreGroup> GenreList = new List<GenreGroup> { new GenreGroup("Mystery", "jd;akfjd;"), new GenreGroup("Fantasy", "dja;fdjkl") };
    public static GenreGroup Mystery = new GenreGroup("Mystery","djfsldfjldjF");
    public static GenreGroup Fantasy = new GenreGroup("Fantasy", "djfsldfjldjF");

    static DataStorage()
    {
        foreach (Book book in AllBookList)
        {
            for (int x = 0; x < book.Genre.Length; x++)
            {
                if (book.Genre[x] == "Mystery")
                {
                    Mystery.Add(book);
                }
                else if (book.Genre[x] == "Fantasy")
                {
                    Fantasy.Add(book);
                }

            }
        }
        GenreList = new List<GenreGroup> { Mystery, Fantasy };
    }
}

我怀疑问题出现在这段代码中，因为这是我改变的。注意：我理解我的代码现在有点奇怪，我明确地定义了GenreList，然后再重新定义它，但我试图确保它不会因为某种原因而无效。谢谢你的帮助

更新：在初始化组件之前放置Debug.WriteLine时，它现在在Debug.WriteLIne上冻结并抛出相同的TypeInitializationEXception

更新：这是GenreGroup和Book

的代码

public class GenreGroup : List<Book>
{
    public string Title { get; set; }
    public string Description { get; set; }

    public GenreGroup(string title, string description)
    {
        Title = title;
        Description = description;
    }
}

public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    public string Summary { get; set; }
    public string[] subjectHeadings { get; set; }
    public string[] Genre { get; set; }
    public string pubYear { get; set; }
}

Answer 1

您在这里缺少初始化：

 public static GenreGroup Mystery; // Init this
 public static GenreGroup Fantasy; // And this

编辑：我刚刚运行了您的代码，没关系。只需清理您的项目并重建它。 VS有很多错误。欢呼声。

Answer 2

listView.ItemsSource = DataStorage.GenreList;

此行将调用static DataStorage()，在此静态构造函数中，Mystery和Fantasy应在调用之前初始化。所以解决方案应该是这样的：

1）在public GenreGroup() { }课程中添加GenreGroup;

2）Mystery类中的初始Fantasy和DataStorage：

    public static GenreGroup Mystery = new GenreGroup();
    public static GenreGroup Fantasy = new GenreGroup();

初始化组件Xamarin中的TypeInitializationException

2 个答案: