UWP - 如果数据源已更改，如何保存列表视图项状态?

Question

我对listviewItem有一个问题，是当您更改数据时，如果他们这样做，但是当您单击另一个项目时它们不会保存在界面中

将文本框绑定到列表视图项时，会发生此问题

MainPage.xaml

<Grid RequestedTheme="Light">
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="818*" />
<RowDefinition Height="auto"/>

</Grid.RowDefinitions>
<TextBox
x:Name="titulo"
Grid.Row="0"
FontSize="40"
PlaceholderText="Ingresa tu titulo"
KeyDown="Titulo_KeyDown"
/>
<StackPanel Grid.Row="1" Orientation="Horizontal">
<ListView
x:Name="listNotas"
Width="450"
Background="DimGray"
SelectionChanged="ListNotas_SelectionChanged">
<ListView.ItemTemplate>
<DataTemplate >
<StackPanel>
<TextBlock Text="{Binding title, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<RichEditBox
x:Name="editor"
Width="760"
HorizontalAlignment="Stretch" />
</StackPanel>
<GridView
Name="stpanel"
Grid.Row="2"
Height="50">
<TextBlock Text="" Name="Tester"/>
</GridView>

主页.xaml.cs

public string editpath = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "Notas.json" );
public ObservableCollection<Notes> Mynotes; 


public MainPage()
{
this.InitializeComponent();
// Load data of Notas.json to Listview
LoadUpdate();
}
private void LoadUpdate()
{
using (StreamReader file = File.OpenText(editpath))
{
var json = file.ReadToEnd();
baseNotes mainnotes = JsonConvert.DeserializeObject<baseNotes>(json);
Mynotes = new ObservableCollection<Notes>();
foreach (var item in mainnotes.notes)
{
Mynotes.Add(new Notes { title = item.title });
} 
listNotas.ItemsSource = null;
listNotas.ItemsSource = Mynotes;
listNotas.SelectedIndex = 0;
}
}
private void ListNotas_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
string json = File.ReadAllText(editpath);
dynamic jsonObj = Newtonsoft.Json.JsonConvert.DeserializeObject(json);
titulo.Text = jsonObj["notes"][listNotas.SelectedIndex]["title"];
}
private void Titulo_KeyDown(object sender, KeyRoutedEventArgs e)
{
#region
string json = File.ReadAllText(editpath);
dynamic jsonObj = Newtonsoft.Json.JsonConvert.DeserializeObject(json);
int indice = listNotas.SelectedIndex;
jsonObj["notes"][indice]["title"] = titulo.Text;
string output = Newtonsoft.Json.JsonConvert.SerializeObject(jsonObj);
File.WriteAllText(editpath, output);
// Show json file text in RicheditBox
editor.TextDocument.SetText(Windows.UI.Text.TextSetOptions.None, output);            

//Problem
Binding myBinding = new Binding();
myBinding.Source = Mynotes[indice];
myBinding.Path = new PropertyPath("title");
myBinding.Mode = BindingMode.TwoWay;
myBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
BindingOperations.SetBinding(titulo, TextBox.TextProperty, myBinding);
#endregion
}

型号：笔记.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.UI.Xaml.Controls;
namespace Realtimejsonedit
{
public class Notes : INotifyPropertyChanged
{
public int created { get; set; }

//public string title { get; set; }
private string Title;
public string title
{
get { return Title; }
set {
Title = value;
NotifyPropertyChanged("title");
}
}
public string text { get; set; }
public int id { get; set; }
public int updated { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}

}
public class baseNotes
{
public List<Notes> notes { get; set; }
} 
}

正如我在执行绑定时所说的问题，但是在执行 ListNotas.SelectionChanged 时，保存在 json 文件中的值会更改，但它们不会保留在列表视图项中，尽管绑定在 Keydown 事件中而不是在 ListNotas 中。选择已更改。

问题： https://i.stack.imgur.com/WgrS2.gif

我想要实现的目标： https://i.stack.imgur.com/wnMBq.gif

Answer 1

UWP - 如果数据源已更改，如何保存列表视图项状态？

问题是您在事件中重复设置绑定Titulo_KeyDown。根据您的要求，您可以绑定一次列表视图选择项。有关更多信息，请参阅以下步骤：

视图模型

public class ViewModel : INotifyPropertyChanged
{
public string editpath = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "Notas.json");
public ObservableCollection<Notes> Mynotes { get; set; }
public ViewModel()
{
LoadUpdate();
SetSelectIndex(0);
}
private void SetSelectIndex(int index)
{
SelectItem = Mynotes[index];
}
private void LoadUpdate()
{
using (StreamReader file = File.OpenText(editpath))
{
var json = file.ReadToEnd();
baseNotes mainnotes = JsonConvert.DeserializeObject<baseNotes>(json);
Mynotes = new ObservableCollection<Notes>();
foreach (var item in mainnotes.notes)
{
Mynotes.Add(new Notes { title = item.title });
}
}
}
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private Notes _selectItem;
public event PropertyChangedEventHandler PropertyChanged;
public Notes SelectItem
{
get
{
return _selectItem;
}
set
{
_selectItem = value;
OnPropertyChanged();
}
}
}

哈姆勒

<Page.DataContext>
<local:ViewModel />
</Page.DataContext>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="818*" />
<RowDefinition Height="auto" />
</Grid.RowDefinitions>
<TextBox
x:Name="titulo"
Grid.Row="0"
FontSize="40"
PlaceholderText="Ingresa tu titulo"
Text="{Binding SelectItem.title, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
TextChanged="Titulo_TextChanged"
/>
<StackPanel Grid.Row="1" Orientation="Horizontal">
<ListView
x:Name="listNotas"
Width="450"
Background="DimGray"
ItemsSource="{Binding Mynotes}"
SelectedItem="{Binding SelectItem, Mode=TwoWay}"
>
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding title, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<RichEditBox
x:Name="editor"
Width="760"
HorizontalAlignment="Stretch"
/>
</StackPanel>
<GridView
Name="stpanel"
Grid.Row="2"
Height="50"
>
<TextBlock Name="Tester" Text="" />
</GridView>
</Grid>

代码隐藏(将数据写入 json(

public sealed partial class MainPage : Page
{
private dynamic jsonObj;
public string editpath = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "Notas.json");
public ObservableCollection<Notes> Mynotes;
public MainPage()
{
this.InitializeComponent();
string json = File.ReadAllText(editpath);
jsonObj = Newtonsoft.Json.JsonConvert.DeserializeObject(json);
}
private void Titulo_TextChanged(object sender, TextChangedEventArgs e)
{
#region
int indice = listNotas.SelectedIndex;
jsonObj["notes"][indice]["title"] = titulo.Text;
string output = Newtonsoft.Json.JsonConvert.SerializeObject(jsonObj);
editor.TextDocument.SetText(Windows.UI.Text.TextSetOptions.None, output);
File.WriteAllText(editpath, output);
#endregion
}
}

这是示例项目。