ISupportIncrementalLoading 인터페이스

정의

네임스페이스:

Microsoft.UI.Xaml.Data

증분 로드를 지원하는 컬렉션 뷰에 대한 호출 계약을 지정합니다.

public interface class ISupportIncrementalLoading

/// [Windows.Foundation.Metadata.ContractVersion(Microsoft.UI.Xaml.WinUIContract, 65536)]
/// [Windows.Foundation.Metadata.Guid(3640243590, 42570, 24568, 134, 142, 32, 78, 20, 79, 44, 244)]
struct ISupportIncrementalLoading

[Windows.Foundation.Metadata.ContractVersion(typeof(Microsoft.UI.Xaml.WinUIContract), 65536)]
[Windows.Foundation.Metadata.Guid(3640243590, 42570, 24568, 134, 142, 32, 78, 20, 79, 44, 244)]
public interface ISupportIncrementalLoading

Public Interface ISupportIncrementalLoading

특성

ContractVersionAttribute GuidAttribute

예제

다음 코드 예제에서는이 인터페이스를 구현 하는 방법을 보여 줍니다. 전체 코드 목록은 XAML 데이터 바인딩 샘플을 참조하세요.

#pragma region Overridable methods

        virtual Concurrency::task<Windows::Foundation::Collections::IVector<Platform::Object^>^> LoadMoreItemsOverride(Concurrency::cancellation_token c, unsigned int count)
        {
            return Concurrency::task<Windows::Foundation::Collections::IVector<Platform::Object^>^>(
                [=]() -> Windows::Foundation::Collections::IVector<Platform::Object^>^ {
                    auto items = ref new Platform::Collections::Vector<Platform::Object^>();
                    return items;
            });
        }
        virtual bool HasMoreItemsOverride()
        {
            return false;
        }

#pragma endregion 

        IncrementalLoadingBase()
        {
            _storage = ref new Platform::Collections::Vector<Platform::Object^>();
            _storage->VectorChanged += ref new Windows::Foundation::Collections::VectorChangedEventHandler<Platform::Object^>(this, &IncrementalLoadingBase::_storageVectorChanged);
            _busy = false;
            _isVectorChangedObserved = false;
        }

    public:

        virtual Windows::Foundation::IAsyncOperation<Windows::UI::Xaml::Data::LoadMoreItemsResult>^ LoadMoreItemsAsync(unsigned int count)
        {
            if (_busy)
            {
                throw ref new Platform::FailureException("Only one operation in flight at a time");
            }

            _busy = true;

            return Concurrency::create_async([=](Concurrency::cancellation_token c) {
                return LoadMoreItemsAsync(c, count)
                    .then([=](Windows::UI::Xaml::Data::LoadMoreItemsResult result) -> Windows::UI::Xaml::Data::LoadMoreItemsResult {
                        _busy = false;
                        return result;
                });
            });
        }

        property bool HasMoreItems
        {
            virtual bool get() { return HasMoreItemsOverride(); }
        }

#pragma endregion 

#region ISupportIncrementalLoading

public bool HasMoreItems
{
    get { return HasMoreItemsOverride(); }
}

public Windows.Foundation.IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
{
    if (_busy)
    {
        throw new InvalidOperationException("Only one operation in flight at a time");
    }

    _busy = true;

    return AsyncInfo.Run((c) => LoadMoreItemsAsync(c, count));
}

#endregion 

#region INotifyCollectionChanged

public event NotifyCollectionChangedEventHandler CollectionChanged;

#endregion 

#region Private methods

async Task<LoadMoreItemsResult> LoadMoreItemsAsync(CancellationToken c, uint count)
{
    try
    {
        var items = await LoadMoreItemsOverrideAsync(c, count);
        var baseIndex = _storage.Count;

        _storage.AddRange(items);

        // Now notify of the new items
        NotifyOfInsertedItems(baseIndex, items.Count);

        return new LoadMoreItemsResult { Count = (uint)items.Count };
    }
    finally
    {
        _busy = false;
    }
}

void NotifyOfInsertedItems(int baseIndex, int count)
{
    if (CollectionChanged == null)
    {
        return;
    }

    for (int i = 0; i < count; i++)
    {
        var args = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, _storage[i + baseIndex], i + baseIndex);
        CollectionChanged(this, args);
    }
}

#endregion

#region Overridable methods

protected abstract Task<IList<object>> LoadMoreItemsOverrideAsync(CancellationToken c, uint count);
protected abstract bool HasMoreItemsOverride();

#endregion 

#region State

List<object> _storage = new List<object>();
bool _busy = false;

#endregion 

속성

HasMoreItems

증분 로드 구현을 지원하는 sentinel 값을 가져옵니다.

메서드

LoadMoreItemsAsync(UInt32)

보기에서 증분 로드를 초기화합니다.

추가 정보

• Binding
• XAML 데이터 바인딩 샘플
• 데이터 바인딩 심층 분석