Xamarin 表单列表视图项目源未更新

Question

我的 xamarin 表单列表视图有问题。我创建了一个列表视图，其中包含绑定到自定义类列表的项目源。在 app.xaml.cs 中，我有完全相同的列表。在另一种形式中，我正在更新驻留在 app.xaml.cs 中的列表。当带列表视图的第一个表单恢复时，在出现时我设置了绑定到 app.xaml.cs 中列表的本地列表。但是，列表视图 UI 中的项目不会更新。有人可以帮我解决这个问题吗？

MainPage.xaml（带有列表视图）：

`

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="TrackExpensesApp.MainPage">

        <ContentPage.ToolbarItems>
            <ToolbarItem Text="+"
                        Clicked="OnAddExpenseClicked" />
        </ContentPage.ToolbarItems>

        

    <ListView x:Name="ExpenseEntriesListView"
                        ItemsSource="{Binding ExpenseEntries}"
                        SelectionMode="Single"
                        ItemSelected="ExpenseEntriesItemSelected">
        <ListView.ItemTemplate>
            <DataTemplate>
                <Grid Padding="10"
                                RowDefinitions="Auto, *"
                                ColumnDefinitions="Auto, *">
                    <Label Grid.ColumnSpan="2"
                                    Text="{Binding Name}"
                                    VerticalOptions="End" />
                    <Label Grid.Row="1"
                                    Text="{Binding DateCreated}"
                                    VerticalOptions="End" />
                    <Label Grid.Row="1"
                                    Grid.Column="1"
                                    Text="{Binding Category}"
                                    VerticalOptions="End" />
                </Grid>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</ContentPage>

` MainPage.xaml.cs（带列表视图）：

`

public partial class MainPage : ContentPage
    {
        public IList<ExpenseEntry> ExpenseEntries { get; set; }

        public MainPage()
        {
            InitializeComponent();
        }

        async void OnAddExpenseClicked(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new ExpensesEntryPage());
        }

        protected override void OnAppearing()
        {
            ExpenseEntries = (Application.Current as TrackExpensesApp.App).ExpenseEntries;
            
            BindingContext = this;
        }

        async void ExpenseEntriesItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            ExpenseEntry selectedItem = e.SelectedItem as ExpenseEntry;

            await Navigation.PushAsync(new ExpensePage());
        }
    }

`

App.xaml.cs：

`

public partial class App : Application
    {
        public IList<ExpenseEntry> ExpenseEntries { get; set; }
        public IList<string> Categories { get; set; }

        public App()
        {
            InitializeComponent();

            // Load in all expenses before loading in the main page
            ExpenseEntries = new List<ExpenseEntry>();

            Categories = new List<string>();
            Categories.Add("Monthly");
            Categories.Add("Vacation");
            Categories.Add("Other");

            MainPage = new NavigationPage(new MainPage());

            BindingContext = this;
        }

        protected override void OnStart()
        {
        }

        protected override void OnSleep()
        {
        }

        protected override void OnResume()
        {
        }
    }

` 如果有人能尽快回复我，我将不胜感激。谢谢！

Answer 1

我们需要在setter方法中调用OnPropertyChanged来通知属性发生了变化，这样UI就会随之改变。

主页

如下修改你的代码

private IList<string> expenseEntries;
public IList<string> ExpenseEntries { 
  get
  {
      return expenseEntries;
  }
  set 
  {
      expenseEntries = value;
      OnPropertyChanged();  //add this line
  } 
}