Question

这是我的项目树：

该项目是一个简单的图书经理。它与sqlite数据库进行交互。

YourBooks类如下：

public sealed partial class YourBooks : Page
{
    private ObservableCollection<Book> Books;

    public YourBooks()
    {
        this.InitializeComponent();

        DatabaseManager.InitializeDatabase();
        Books = DatabaseManager.GetBooks();
    }

    private async void Add_a_book_Clicked(object sender, RoutedEventArgs e)
    {
        //This doesn't matter
    }
}

DatabaseManager类充当应用程序和数据库之间的中间人。这是代码：

class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    public string ISBN { get; set; }
    public int Quantity { get; set; }
    public string CoverImage { get; set; }
}

class DatabaseManager
{
    public static void InitializeDatabase()
    {
        using (SqliteConnection db = new SqliteConnection("FileName= MyBooks.db"))
        {
            db.Open();

            string command = "create table if not exists MyBooks " +
                             "(title text primary key not null, author text not null, isbn text not null, quantity integer not null, " +
                             "CoverImage text not null)";

            SqliteCommand createTable = new SqliteCommand(command, db);

            SqliteDataReader reader = createTable.ExecuteReader();

            while(reader.Read())
            { }
        }
    }

    public static ObservableCollection<Book> GetBooks()
    {
        using (SqliteConnection db = new SqliteConnection("FileName=MyBooks.db"))
        {
            db.Open();

            string command = "select title, author, quantity, CoverImage from MyBooks";

            SqliteCommand getBooks = new SqliteCommand(command, db);

            SqliteDataReader dataReturned = getBooks.ExecuteReader();

            ObservableCollection<Book> books = new ObservableCollection<Book>();
            while(dataReturned.Read())
            {
                books.Add(new Book
                {
                    Title = dataReturned.GetString(0),
                    Author = dataReturned.GetString(1),
                    Quantity = dataReturned.GetInt32(2),
                    CoverImage = dataReturned.GetString(3)
                });
            }

            return books;
        } 
    }

    public static void AddBook(string title, string author, string isbn, int quantity, string coverImageLocation)
    {
        using (SqliteConnection db = new SqliteConnection("FileName=MyBooks.db"))
        {
            db.Open();

            SqliteCommand command = new SqliteCommand
            {
                CommandText = "insert into MyBooks values (@title, @author, @isbn, @quantity, @coverImage)",
                Connection = db
            };

            command.Parameters.AddWithValue("@title", title);
            command.Parameters.AddWithValue("@author", author);
            command.Parameters.AddWithValue("@isbn", isbn);
            command.Parameters.AddWithValue("@quantity", quantity);
            command.Parameters.AddWithValue("@coverImage", coverImageLocation);

            command.ExecuteReader();
        }
    }
}

在NewBooks类中，我这样更新数据库：

DatabaseManager.AddBook(BookNameTextBox.Text, AuthorTextBox.Text, ISBNTextBox.Text, Convert.ToInt32(Quantity.Text), destinationFile.Path);

我想通知YourBooks类数据库已更改。在UWP之前，我对Qt的了解很少。并且在Qt中它具有信号和时隙机制。因此，您要做的就是定义一个可以触发并调用该插槽的信号。

如何从NewBook通知YourBooks数据库已更改，以便它可以更新。

Answer 1

在Book类（或任何您调用的类型）中实现INotifyPropertyChanged接口，并在每次将其属性设置为新值时引发PropertyChanged事件。

然后，视图中绑定到相应属性的任何UI元素都会自动更新。

如果将新书添加到数据库，则还应该向Book绑定到的ObservableCollection<T>添加新的GridView对象。

在您的情况下，您可以从DatabaseManager类中引发一个事件，并在YourBooks类中对该事件进行处理。

如何在UWP中实现信号插槽

1 个答案: