ListView不会更新到Windows 10的UWP上的ObservableCollection中的新插入项目

Question

我试图了解所有连接如何，我需要一些帮助。 到目前为止，我可以做插入，更新，删除到sqlite数据库，但我不能让UI显示从数据库的更改自动没有我更新ListView上的ItemsSource每当对数据库进行更改。即：

在我App.xaml.cs

public App() 
     { 
      this.InitializeComponent(); 
      this.Suspending += OnSuspending; 

      //Connection to the database and create the table if not there 
      string path = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite"); 
      SQLiteConnection conn = new SQLiteConnection(path); 
      conn.CreateTable<CheckListItemModel>(); 
     } 

比我MainPage.xaml中我有两个按钮，一个简单的页面和列表视图

<Page 
    x:Class="Personal_Checklist_2.MainPage" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:local="using:Personal_Checklist_2" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    mc:Ignorable="d"> 

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="100" /> 
      <RowDefinition Height="*" /> 
     </Grid.RowDefinitions> 
     <StackPanel Grid.Row="0" Orientation="Horizontal" > 
      <Button Content="Add Sample To Db" Click="Add_Sample_To_Db_Click" Margin="10,0,10,0" /> 
      <Button Content="Clear Tasks" Click="Clear_Tasks_Click" /> 
     </StackPanel> 

     <ListView Name="lvListView" Grid.Row="1" > 
      <ListView.ItemTemplate> 
       <DataTemplate> 
        <StackPanel Orientation="Horizontal"> 
         <TextBlock Text="{Binding Title}" /> 
         <TextBlock Text="{Binding Id}" /> 
        </StackPanel> 
       </DataTemplate> 
      </ListView.ItemTemplate> 
     </ListView> 
    </Grid> 
</Page> 

在MainPage.xaml.cs代码隐藏我也保持简单，因为我知道只是添加新行到表中并清除表

using Personal_Checklist_2.DataModels; 
using System.IO; 
using System.Linq; 
using SQLite; 
using Windows.UI.Xaml; 
using Windows.UI.Xaml.Controls; 
using System.Collections.ObjectModel; 

namespace Personal_Checklist_2 
{ 
    public sealed partial class MainPage : Page 
    { 
     static string path = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite"); 
     ObservableCollection<CheckListItemModel> Tasks = new ObservableCollection<CheckListItemModel>(); 

     public MainPage() 
     { 
      this.InitializeComponent(); 
      using (var conn = new SQLiteConnection(path)) 
      { 
       var query = conn.Table<CheckListItemModel>(); 
       Tasks = new ObservableCollection<CheckListItemModel>(query.ToList()); 

       lvTasksList.ItemsSource = Tasks.ToList(); //<<<--- If I dont do this, list is not updated 
      } 
     } 

     private void Add_Sample_To_Db_Click(object sender, RoutedEventArgs e) 
     { 
      var Task = new CheckListItemModel() 
      { 
       taskTitle = "Sample Task" 
      }; 

      using (var conn = new SQLiteConnection(path)) 
      { 
       conn.Insert(Task); 
       var query = conn.Table<CheckListItemModel>(); 
       Tasks = new ObservableCollection<CheckListItemModel>(query.ToList()); 
       lvTasksList.ItemsSource = Tasks.ToList(); //<<<--- If I dont do this, list is not updated 
      } 
     } 

     private void Clear_Tasks_Click(object sender, RoutedEventArgs e) 
     { 
      using (var conn = new SQLiteConnection(path)) 
      { 
       conn.DeleteAll<CheckListItemModel>(); 
       var query = conn.Table<CheckListItemModel>(); 
       Tasks = new ObservableCollection<CheckListItemModel>(query.ToList()); 
       lvTasksList.ItemsSource = Tasks.ToList(); //<<<--- If I dont do this, list is not updated 
      } 
     } 
    } 
} 

数据库表的模型看起来像这样CheckListItemModel.cs

using SQLite; 
using System; 
using System.ComponentModel; 

namespace Personal_Checklist_2.DataModels 
{ 
    class CheckListItemModel : INotifyPropertyChanged 
    { 
     #region Private fields on DataModel 
     private string _taskTitle; 
     #endregion 

     #region Public properties on DataModel 
     [PrimaryKey, AutoIncrement] 
     public int taskId { get; set; } 

     public string taskTitle 
     { 
      get { return _taskTitle; } 
      set { _taskTitle = value; NotifyPropertyChanged("taskTitle"); } 
     } 
     #endregion 

     #region INotifyPropertyChanged implementation 
     public event PropertyChangedEventHandler PropertyChanged; 
     private void NotifyPropertyChanged(String propertyName) 
     { 
      PropertyChangedEventHandler handler = PropertyChanged; 
      if (null != handler) 
      { 
       handler(this, new PropertyChangedEventArgs(propertyName)); 
      } 
     } 
     #endregion 
    } 
} 

不过，这并不正确看我这个样子。有没有办法实现这一点，而无需设置listview.ItemsSource每次在db.sqlite中的一些变化，以及如何？

Answer 1

你投了你的ObservableCollection toList（）这就是为什么它不更新。将其更改为：

lvTasksList.ItemsSource = Tasks;

而当你添加一个项目你不必再次读取数据库

private void Add_Sample_To_Db_Click(object sender, RoutedEventArgs e) 
    { 
     var Task = new CheckListItemModel() 
     { 
      taskTitle = "Sample Task" 
     }; 

     using (var conn = new SQLiteConnection(path)) 
     { 
      conn.Insert(Task); 
     } 
     Tasks.Add(Task); 
    } 

Answer 2

您每次都创建一个新的ObservableCollection，而不是绑定到单个ObservableCollection并更改其中的项目。

因此，请保留Tasks作为单个ObservableCollection并根据数据库查询结果更新其内容。