Es mag komisch klingen und ich weiß, dass die Verwendung von ISupportIncrementalLoading für die Ansichtsebene von MVVM ist.Was ist die beste Vorgehensweise für die Verwendung von ISupportIncrementalLoading in MVVM?
Ich aktualisiere jetzt die Itemquelle meiner ListView in der Datei xaml.cs, sobald die Collection-Eigenschaft im ViewModel aktualisiert wird. Gibt es andere (und bessere) Lösungen für diese Art von Bedarf?
Hallo Ich habe viele Male mit ISupportIncrementalLoading mit MVVM Muster arbeiten.
Ich mag es zu erstellen und unabhängige Klasse, die alle die Logik zu kapseln, um alle Daten zu laden Ich lasse hier ein Beispiel für eine meiner Klassen Ich hoffe, das hilft.
Ich habe eine IncrementalCollectionBase erstellt, um den gesamten Code in allen benutzerdefinierten Sammlungen wiederzuverwenden.
public class IncrementalCollectionBase<T> : ObservableCollection<T>,
ISupportIncrementalLoading,
INotifyPropertyChanged,
IIncrementalCollection<T>, IDisposable
{
private long totalRecordCount;
public int PageNo { get; set; }
public int PageSize { get; set; }
public int PageCount { get; set; }
public long TotalRecordCount
{
get
{
return this.totalRecordCount;
}
set
{
this.totalRecordCount = value;
OnPropertyChanged(new PropertyChangedEventArgs("TotalRecordCount"));
}
}
public IncrementalCollectionBase()
{
this.FeedSize = 10;
}
public CancellationTokenSource CancelToken { get; set; }
public bool HasMoreItems { get; set; }
private bool isLoading { get; set; }
public bool IsLoading
{
get
{
return isLoading;
}
set
{
isLoading = value;
OnPropertyChanged(new PropertyChangedEventArgs("IsLoading"));
}
}
public int FeedSize { get; set; }
public event EventHandler<LoadIncrementalCollectionChanged> OnLoadIncrementalCollectionChanged;
public void Cancel()
{
try
{
CancelToken?.Cancel();
}
catch (Exception ex)
{
}
}
public virtual Task<IEnumerable<T>> LoadDataAsync()
{
throw new NotImplementedException();
}
public virtual IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
{
throw new NotImplementedException();
}
public virtual void Setup(CancellationTokenSource cancelToken = null)
{
CancelToken = cancelToken;
}
public void Dispose()
{
try
{
Cancel();
Items.Clear();
}
catch (Exception)
{
}
}
}
Nachdem dies zu tun, erstelle ich meine benutzerdefinierte Sammlung
public class MyCustomEntityIncrementalCollection : IncrementalCollectionBase<CustomEntity>
{
private ISearchentityService searchentityService = null;
private bool searchMode = false;
private string key = "";
private bool IsFirstSearchResult = true;
private IentityService entityService = null;
private ILoginService loginService = null;
private IToastService toastService = null;
public MyCustomEntityIncrementalCollection(CancellationTokenSource cancelToken, int feedSize = 10)
{
Setup(cancelToken);
this.FeedSize = feedSize;
toastService = IoC.Get<IToastService>();
searchentityService = IoC.Get<ISearchentityService>();
loginService = IoC.Get<ILoginService>();
entityService = IoC.Get<IentityService>();
}
private async Task<IEnumerable<CustomEntity>> Search()
{
try
{
if (IsFirstSearchResult)
{
var result = await searchentityService.SearchAsync(key, loginService.CurrentUser.Id, CancelToken, loginService.CurrentToken.AccessToken, 1, 50);
if (result == null)
{
toastService.ShowAsync("Sin resultados", "No se han encontrado coincidencias");
}
PageNo = result.paging.pageNo;
PageCount = result.paging.pageCount;
PageSize = result.paging.pageSize;
TotalRecordCount = result.paging.totalRecordCount;
IsFirstSearchResult = false;
return result.data;
}
else
{
var result = await searchentityService.SearchAsync(key, loginService.CurrentUser.Id, CancelToken, loginService.CurrentToken.AccessToken, (PageNo + 1), 50);
PageNo = result.paging.pageNo;
PageCount = result.paging.pageCount;
PageSize = result.paging.pageSize;
TotalRecordCount = result.paging.totalRecordCount;
return result.data;
}
}
catch (Exception)
{
}
return null;
}
public async Task TurnOnSearchMode(string keyword)
{
if (string.IsNullOrEmpty(keyword) || string.IsNullOrWhiteSpace(keyword))
throw new Exception(" keyword is invalid");
searchMode = true;
key = keyword;
IsFirstSearchResult = true;
this.ClearItems();
await Task.Delay(500);
await LoadMoreItemsAsync(1);
}
public async Task TurnOffSearchMode()
{
searchMode = false;
IsFirstSearchResult = true;
key = "";
this.ClearItems();
await LoadMoreItemsAsync(1);
}
public override async Task<IEnumerable<CustomEntity>> LoadDataAsync()
{
try
{
if (this.Items.Count == 0)
{
var result = await entityService.MyEntities(CancelToken, loginService.CurrentToken.AccessToken, 1, FeedSize);
if (result != null && result.data != null)
{
PageNo = result.paging.pageNo;
PageCount = result.paging.pageCount;
PageSize = result.paging.pageSize;
TotalRecordCount = result.paging.totalRecordCount;
return result.data;
}
}
else
{
var result = await entityService.MyEntities(CancelToken, loginService.CurrentToken.AccessToken, (PageNo + 1), FeedSize);
PageNo = result.paging.pageNo;
PageCount = result.paging.pageCount;
PageSize = result.paging.pageSize;
TotalRecordCount = result.paging.totalRecordCount;
return result.data;
}
}
catch (Exception)
{
}
return null;
}
public override IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
{
return AsyncInfo.Run(async c =>
{
await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Low, (() =>
{
IsLoading = true;
}));
if (searchMode == false)
{
try
{
var data = await LoadDataAsync();
if (data != null && data.Any())
{
HasMoreItems = true;
}
else
{
HasMoreItems = false;
}
if (data != null)
{
await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, (() =>
{
foreach (var item in data)
{
this.Add(item);
}
})).AsTask().ContinueWith(z => { data = null; });
}
}
catch (Exception ex)
{
Debug.WriteLine("Se ha producido un error al buscar videos");
}
}
else
{
try
{
var data = await Search();
if (data != null && data.Any())
{
HasMoreItems = true;
}
else
{
HasMoreItems = false;
}
if (data != null)
{
await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, (() =>
{
foreach (var item in data)
{
this.Add(item);
}
})).AsTask().ContinueWith(z => { data = null; });
}
}
catch (Exception ex)
{
Debug.WriteLine("Se ha producido un error al buscar videos");
}
}
await Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Low, (() =>
{
IsLoading = false;
}));
return new LoadMoreItemsResult() { Count = count };
});
}
}
Ich nenne schließlich nur die Anfangslast in meiner Ansicht Modell im Konstruktor oder einem anderen Ort.
this.MyEntities = new Infrastructure.Collections.MyCustomEntityAppraisalIncrementalCollection(cancelToken, 20);
await MyEntities.LoadMoreItemsAsync(1);