为什么刷新拉图标一直在刷新

Question

我有这个RefreshCommand，我用它来刷新"；音符"；，但当我刷新页面时，它不会刷新2秒，然后只给我笔记，而是会不断刷新，这不是我希望它做的，而且它会滞后于应用程序。

这是代码

MyNotePage.xaml

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:model="clr-namespace:MyApp.Models"
xmlns:mvvm="clr-namespace:MvvmHelpers;assembly=MvvmHelpers"
xmlns:viewmodels="clr-namespace:MyApp.ViewModels"
xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
x:Class="MyApp.MyNotePage"
x:DataType="viewmodels:MyNoteViewModel"
BackgroundColor="White">
<ContentPage.BindingContext>
<viewmodels:MyNoteViewModel/>
</ContentPage.BindingContext>
<ContentPage.Resources>
<ResourceDictionary>
<xct:ItemSelectedEventArgsConverter x:Key="ItemSelectedEventArgsConverter"/>
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.ToolbarItems>
<ToolbarItem Text="Add" Command="{Binding AddCommand}"/>
</ContentPage.ToolbarItems>
<ListView
BackgroundColor="Transparent"
CachingStrategy="RecycleElement"
HasUnevenRows="True"
IsPullToRefreshEnabled="True"
IsRefreshing="{Binding IsBusy, Mode=OneWay}"
ItemsSource="{Binding Note}"
RefreshCommand="{Binding RefreshCommand}"
RefreshControlColor="DarkViolet"
SelectionMode="None"
SeparatorVisibility="None">
<ListView.ItemTemplate>
<DataTemplate x:DataType="model:Note">
<ViewCell>
<ViewCell.ContextActions>
<MenuItem
Command="{Binding Source={Binding MyNotePage}, Path=BindingContext.RemoveCommand}"
CommandParameter="{Binding .}"
IsDestructive="True"
Text="Delete"/>
</ViewCell.ContextActions>
<Grid Padding="10">
<Frame CornerRadius="20" HasShadow="True">
<StackLayout Orientation="Horizontal">
<StackLayout VerticalOptions="Center">
<Label
FontSize="Large"
Text="{Binding Name}"
VerticalOptions="Center"/>
<Label
FontSize="Small"
Text="{Binding Id}"
VerticalOptions="Center"/>
</StackLayout>
</StackLayout>
</Frame>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

MyNotePage.xaml.cs

namespace MyApp
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class MyNotePage
{
public MyNotePage()
{
InitializeComponent();
}

}
}

MyNoteViewModel.cs

namespace MyApp.ViewModels
{
public class MyNoteViewModel : ViewModelBase
{
public ObservableRangeCollection<Note> Note { get; }
public AsyncCommand RefreshCommand { get; }
public AsyncCommand AddCommand { get; }
public AsyncCommand<Note> RemoveCommand { get; }
public new bool IsBusy { get; private set; }
public MyNoteViewModel()
{
Note = new ObservableRangeCollection<Note>();
RefreshCommand = new AsyncCommand(Refresh);
AddCommand = new AsyncCommand(Add);
RemoveCommand = new AsyncCommand<Note>(Remove);
}
async Task Add()
{
var name = await App.Current.MainPage.DisplayPromptAsync("Notes", "Enter your notes here");
await NoteService.AddNote(name);
await Refresh();
}
async Task Remove(Note note)
{
await NoteService.RemoveNote(note.Id);
await Refresh();
}

async Task Refresh()
{
IsBusy = true;
await Task.Delay(2000);
Note.Clear();
var notes = await NoteService.GetNote();
Note.AddRange(notes);
IsBusy = false;
}
}
}

和NoteService.cs

namespace MyApp.Services
{
public static class NoteService
{
static SQLiteAsyncConnection db;
static async Task Init()
{
if (db != null)
return;
{
var databasePath = Path.Combine(FileSystem.AppDataDirectory, "MyData.db");
db = new SQLiteAsyncConnection(databasePath);
await db.CreateTableAsync<Note>();
}
}
public static async Task AddNote(string name)
{
await Init();
var note = new Note()
{
Name = name,
};
await db.InsertAsync(note);
}
public static async Task RemoveNote(int id)
{
await Init();
await db.DeleteAsync<Note>(id);
}
public static async Task<IEnumerable<Note>> GetNote()
{
await Init();
var note = await db.Table<Note>().ToListAsync();
return note;
}
}
}

也许这与我很忙有关？我不知道我是否设置得当。bool确实从false变为true，但看起来并没有起到相反的作用来停止刷新。谢谢你的帮助。

Answer 1

我在上一个问题中向您指出了这一点。IsBusy不会引发PropertyChanged事件，因此UI永远不会收到通知