2.1 other stone-ArcMap plug-in mechanism

Plug-ins we are preparing to design GIS Application Framework Nbgis ESRI Of ArcMap The software is a simulated object, so it is necessary for readers to understand ArcMap Program.

ArcMapNot based on. NetProgram developed by the Mechanism, which usesC ++Developed, despite this, except for plug-in recognition. NetFramework andComThe plug-in framework is different, and other steps are very similar. You can design a plug-inGISThe Application Framework process provides reference.

The core of the plug-in architecture is the communication between the framework Host Program and the plug-in object. That is, how the Host Program recognizes plug-in objects and establishes event associations with plug-in objects. This process includes the following points:

How does the Host Program identify plug-in objects?

ArcMapIsComThe application of the mechanism, andMS Office SystemSimilarly, when it is installed on a hard disk,ArcMapAll dynamic link librariesDLLFile registration information will be written to different "component directories" in the Registry "(Component categories.

Arcmap.exeWhen the program startsArcMapRelatedComponent categoriesFind information about the relevant plug-in objects and initialize them based on the information.

The plug-in referred to in this book refers to the ability to form a user interface (User Interface,UI) And can interact with users inArcMapAs a command button (Icommand), A tool button (Itool), A toolbar (Itoolbardef), A menu bar (Imenudef) Or a floating form (Idockablewindow). For exampleFigure2 limit 2As shown in.UIAll objects are generated based on the attributes of the plug-in objects.UILayer representation.

 

Figure2 ‑ 2 ArcMapProgram Interface

After the Host Program obtains the corresponding plug-in object information, it dynamically createsUIObject.

Plug-inUIHow can an object be initialized?

When the host ProgramArcmap.exeAfter obtaining information about the plug-in object from the registry and generating the plug-in object in the memory (note that the plug-in object is stillUITo generate plug-ins Based on the plug-in objects.UIObject.

plug-in UI object initialization includes three aspects: first, the host Program carries the UI information generation actual UI layer object, take icommand as an example, the Host Program obtains the icon and tooltip , name , Category , message , in the UI Generate a UI command command object for interaction, see figure 2 rows 2 .

The second is that the Host Program will create two public variables that will carry the information and interaction methods of the Host Program.ArcMapModerateApplicationAndThisdocumentTwo objects.Arcmap.exeSetApplicationObject plug-inUIThe object's initialization function is passed to the plug-inUIObject. The initialization function is as follows:

Private sub icommand_oncreate (byval hook as object)

'HookThe parameter is a pointArcMapHost Program pointer

'M_pappIs a variable for the plug-in to use the host Program. The plug-in can use this variable to obtain information about the main program.

Set m_papp = hook

End sub

In this way, the communication bridge between the host Program and the plug-in object is established.

Third, the host program adds a plug-in objectUIThe interaction channel between the object and the plug-in object is established. The host program implements this through the "event mechanism" when the userUIClick a plug-in on the pageUIThe host program can call the correct plug-in object through the function pointer and callback function to complete specific operations.

How plug-in objects generate theirUIObject?

The plug-in objects are differentUIFormat appears on the host Program. This is the plug-inUIObject initialization. BecauseArcMapThe visualization components in are dividedIcommand,Itool,Itoolbardef,ImenudefAndIdockablewindowWhen the host Program obtains information about a plug-in component, it generates differentUILayer components.

If you write an extensionDLL, Which includesIcommandType andItoolbardefType, andIcommandTypeUIObjects are placed inItoolbardefOfUIDuring parsing, the host Program will generateIcommandObjectUIObject andItoolbardefOfUIObject, and thenIcommandOfUIObject associatedItoolbardefInUIThe effect on the layer is a tool bar with command buttons.

TheseUIThe Host Program is responsible for the process of layer parsing and generation. Plug-In developers do not need to consider this issue.

Plug-inUIHow do I interact with the plug-in when an object is triggered?

Plug-in objectUIHow Objects interact with plug-in objects when triggered by users is perhaps the most interesting part of the plug-in framework. InComBy binding function pointers and callback functions, the host Program will know which object's function needs to be called when a button is pressed to implement the functions required for the event. In. NET FrameworkEvent Association is called a "delegate"(Delegate)In the following sections, we will explain the principle and application of the delegation mechanism.

Figure2 limit 3ShownArcmap.exeThe whole process of starting and loading the plug-in:

 

Figure2 ‑ 3 ArcMapStartup Process