【发布时间】：2022-08-14 07:26:50
【问题描述】：
我有这个 RefreshCommand 用于刷新 \"notes\" 的数据库，但是当我刷新页面时，不是刷新 2 秒然后只是给我笔记，而是不断刷新，这不是什么我希望它这样做，而且它落后于应用程序。
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 IsBusy 有关？我不知道我是否正确设置了它。 bool 确实从 false 变为 true，但看起来它并没有做相反的事情来停止刷新。谢谢您的帮助。
标签： c# sqlite xamarin xamarin.forms