壳Namespace引伸： 增加习惯指令舱项目

概要

在我 更加早期的岗位我显示了如何使用缺省IShellView实施(亦称DefView)创造壳Namespace引伸。 您也许从样品已经注意了的一件事是指令舱是空隙缺省项目例如“组织”和“看法”。

如果您开发您自己的Namespace并且想要包括系统设定按钮并且/或者增加您自己的元素到指令舱，您怎么完成此？ 答复： 您必须实施 IExplorerCommand, IExplorerCommandProvider 并且 IEnumExplorerCommand 接口。

在我之下描述什么每一个接口使用为，并且什么您需要做适当地实施他们用您的代码。

IExplorerCommandProvider

在您的Namespace被装载之后，壳将请求您的Namespace IExplorerCommandProvider的事例。 这个接口暴露二个方法： GetCommand和GetCommands。 壳叫GetCommand方法检索匹配由供应的GUID的一个具体IExplorerCommand对象(每个命令是由GUID确定的)。 GetCommands方法叫检索IEnumExplorerCommand事例。 这个对象列举所有IExplorerCommand事例为namespace。

您Namespace为它的IExplorerCommandProvider的实施被询问通过它的CreateViewObject的IShellFolder的实施。 REFIID通过对CreateViewObject将是IID_IExplorerCommandProvider。 壳然后将使用这个接口检索是实施的您的指令舱项目- IExplorerCommand 接口。

IExplorerCommand

IExplorerCommand接口用于提供项目的出现和行为给探险家的指令舱。 大多方法通过辨认的IShellItemArray什么项目在看法当前被选择。 这信息可以由实施用于定做行为为不同的选择或，如果项目没有被选择。 例如，如果项目没有被选择，您可以希望设置状态对ECS_DISABLED或ECS_HIDDEN对灰色或从指令舱完全地去除项目，分别。

这个接口暴露的方法下述。

方法	描述
EnumSubCommands	退回用于的IEnumExplorerCommand事例列举当前命令的次级命令。 如果GetFlags方法退回ECF_HASSUBCOMMANDS，壳只将叫这个方法。 它这里是重要对笔记，当如此时做是可能的，有次级命令的次级命令没有被鼓励。
GetCanonicalName	检索全局唯一标识符(GUID)与这个命令相关
GetFlags	检索旗子与这个命令相关。 这些旗子在指令舱指定命令的出现和行为。
GetIcon	检索像资源串。 这串是以“myfile.dll， id”的形式。 For example: “shell32.dll,-101”
GetState	Retrieves the state of the command item. This is the first method of the interface that is called. The state that is returned affects the appearance and behavior of the command item. This method also passes a BOOL to let the command implementation know if the slow response rule is in effect.
GetTitle	Retrieves the string to display for the command item.
GetToolTip	Retrieves the string to use in the ToolTip associated with this command item.
Invoke	Called by the Shell when the user has activated a command on the Commands Module.

The above methods GetState and GetFlags return values that determine the appearance and behavior of the item in the Command Module. In the table below are screenshots of the command resulting from the combinations of the flags/states values.

	ECS_ENABLED	ECS_DISABLED	ECS_HIDDEN
NONE
ECF_HASSUBCOMMANDS
ECF_HASSPLITBUTTON
ECF_HIDELABEL
ECF_ISSEPARATOR		N/A
ECF_HASLUASHIELD

	ECS_CHECKBOX	ECS_CHECKBOX| ECS_CHECKED
NONE
ECF_HASSUBCOMMANDS
ECF_HASSPLITBUTTON
ECF_HIDELABEL
ECF_ISSEPARATOR	N/A	N/A
ECF_HASLUASHIELD

*ECS_CHECKBOX and ECS_CHECKED only apply to sub items

** ECF_ISSEPARATOR can only be added as a sub item

Slow Response Rule

The second parameter of the GetState method is a BOOL (fOkToBeSlow) that lets the implementation of IExplorerCommand know if the “slow response rule” is in effect. If this value is FALSE, and your implementation performs slow operations (such as I/O, network calls or calls to out of thread COM objects) then your command should return E_PENDING. This will cause the Commands Module to call the command’s GetState (and other methods) on a background thread with fOkToBeSlow set to TRUE. This prevents slow operations in your implementation from running on the UI thread, thus preventing performance issues.

Command Item Ordering

It is important to note here that the developer of the Namespace Extension has no control over the ordering of command items. For example, you cannot force your command items before the default View and Organize command items or have the View or Organize command items renamed/removed. Items are simply appended to the end of the Commands Module in the order returned from the IEnumExplorerCommand instance.

IEnumExplorerCommand

The IEnumExplorerCommand is returned to the Shell by the GetCommands method of the IExplorerCommandProvider interface. As the name suggests, it permits enumeration of the IExplorerCommand instances by the Shell.

FolderViewImpl Sample Code

The above interfaces have been implemented in the attached Shell Namespace Extension sample code derived from the FolderViewImpl SDK sample. The structure of the command items (as well as sub items) is data-driven from an array of structures that define the command items (see the array of FVCOMMANDITEMs in fvcommands.cpp). This approach was used to make it easy to experiment with the hierarchy of command items as well as their behavior/appearance. The way you implement commands in your Namespace Extension may differ.

The above is a screenshot of the modified SDK sample. Notice we now have the default command items (Organize and Views) as well as our custom items. The Display command item performs the same function as right-clicking items in the view and selecting “Display” from the context menu. The Settings button is used to demonstrate a command item with sub items. All it does is display a message box with the name of the sub item when the user invokes the specified sub item.

It should also be noted that if you are using a custom view in your Namespace by implementing your own IShellView (instead of using DefView) you will need to include an implementation of IFolderView::GetFolder. In your GetFolder implementation you will need to include the ability to QueryService for SID_SFolderView.

Building the FolderView SDK Sample

1. To build the FolderViewImpl sample, be sure to download and install the Windows SDK.
2. Download the modified FolderView SDK sample
3. Launch FolderViewImpl.sln in Visual Studio
4. Open the properties for the project
5. Add a path to the SDK includes to the C/C++ - General page
6. Add a path to the SDK libs to the Linker – General page
7. Build

Installing the FolderView SDK Sample

1. Once you have built the sample, copy the FolderViewImpl.dll and FolderViewImpl.propdesc to the same directory
2. From an elevated cmd window, regsvr32 FolderViewImpl.dll
3. Restart explorer
4. Open explorer to Computer
5. There should be a list item named “FolderView SDK Sample”

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