StorageLibraryChangeTracker.Enable 方法

定义

命名空间:

Windows.Storage

重载

Enable()	为存储库启用更改跟踪。
Enable(StorageLibraryChangeTrackerOptions)	基于更改 ID 对所有或最新更改启用对存储库的更改跟踪。

Enable()

为存储库启用更改跟踪。

public:
 virtual void Enable() = Enable;

void Enable();

public void Enable();

function enable()

Public Sub Enable ()

Enable(StorageLibraryChangeTrackerOptions)

基于更改 ID 对所有或最新更改启用对存储库的更改跟踪。

public:
 virtual void Enable(StorageLibraryChangeTrackerOptions ^ options) = Enable;

/// [Windows.Foundation.Metadata.Overload("EnableWithOptions")]
void Enable(StorageLibraryChangeTrackerOptions const& options);

[Windows.Foundation.Metadata.Overload("EnableWithOptions")]
public void Enable(StorageLibraryChangeTrackerOptions options);

function enable(options)

Public Sub Enable (options As StorageLibraryChangeTrackerOptions)

参数

options

StorageLibraryChangeTrackerOptions

StorageLibraryChangeTrackerOptions 实例。

属性

OverloadAttribute

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

对于仅对最后一个更改 ID 感兴趣的应用程序，系统不会存储所有更改记录，并且不会将存储膨胀到设备上的存储。 在这种情况下，ReadBatchAsync 将始终返回 0 条记录。

另请参阅

• StorageLibraryChangeTrackerOptions