StorageLibraryChangeTrackerOptions 类
定义
重要
一些信息与预发行产品相关,相应产品在发行之前可能会进行重大修改。 对于此处提供的信息,Microsoft 不作任何明示或暗示的担保。
允许调用方在更改跟踪器上调用 EnableWithOptions,以选择跟踪所有更改,包括上次更改 ID 或仅跟踪上次更改 ID。
public ref class StorageLibraryChangeTrackerOptions sealed
/// [Windows.Foundation.Metadata.Activatable(720896, "Windows.Foundation.UniversalApiContract")]
/// [Windows.Foundation.Metadata.ContractVersion(Windows.Foundation.UniversalApiContract, 720896)]
/// [Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
/// [Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
class StorageLibraryChangeTrackerOptions final
[Windows.Foundation.Metadata.Activatable(720896, "Windows.Foundation.UniversalApiContract")]
[Windows.Foundation.Metadata.ContractVersion(typeof(Windows.Foundation.UniversalApiContract), 720896)]
[Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
[Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
public sealed class StorageLibraryChangeTrackerOptions
function StorageLibraryChangeTrackerOptions()
Public NotInheritable Class StorageLibraryChangeTrackerOptions
- 继承
- 属性
Windows 要求
设备系列 |
Windows 10, version 2104 (在 10.0.20348.0 中引入)
|
API contract |
Windows.Foundation.UniversalApiContract (在 v12.0 中引入)
|
示例
// applications are expected to persist the previous value
UINT64 appsLastPersistedChangeId = StorageLibraryLastChangeId::Unknown();
StorageFolder folder = StorageFolder::GetFolderFromPathAsync(L"my folder path").get();
StorageLibraryChangeTracker tracker = folder.TryGetChangeTracker();
if (tracker != nullptr)
{
StorageLibraryChangeTrackerOptions ops;
ops.TrackChangeDetails(false);
tracker.Enable(ops);
StorageLibraryChangeReader reader = tracker.GetChangeReader();
if (reader != nullptr)
{
UINT32 changeId = reader.GetLastChangeId();
if ((changeId == StorageLibraryLastChangeId::Unknown())
{
ScanFolderSlow();
}
else if (changeId == 0)
{
// no changes in the storage folder yet, OR nothing has changed
ProcessNormalApplicationStartup();
}
else if (changeId != appsLastPersistedChangeId)
{
// There have been new changes since we’ve last ran, process them
appsLastPersistedChangeId = changeId;
ScanFolderForChanges();
}
else
{
// changeId and our last persisted change id match, also normal application startup
ProcessNormalApplicationStartup();
}
}
}
注解
默认情况下,在特定库或文件夹上启用更改跟踪器将跟踪所有更改详细信息,并跟踪上次更改 ID。通过将 StorageLibraryChangeTrackerOptions::TrackChangeDetails 设置为 false 并使用 EnableWithOptions(如以下示例所示),系统将仅跟踪使用较少系统存储的最后一个更改 ID。
如果应用程序不需要有关更改的详细信息,建议使用此方法。
构造函数
StorageLibraryChangeTrackerOptions() |
StorageLibraryChangeTrackerOptions 的构造函数,用于为 StorageFolder 或 StorageLibrary 设置更改跟踪器的行为。 |
属性
TrackChangeDetails |
用于确定系统是跟踪每个单独的更改,还是只跟踪给定更改跟踪器的最后一个更改 ID。 |