ArcGIS Engine Developer Guide

C++ APPLICATION PROGRAMMING INTERFACE
Include files
To use these events, you will need to include Ao/AoControls.h in your event
class’s header file.
Implementation details
To initiate listening for these events, you first need to get the interface on which
to Advise (in the example below, IActiveView). Create an instance of your event
class. Call both IEventListenerHelper->Startup and
IEventListenerHelper->AdviseEvents. For these events, you will need to inform
AdviseEvents of the UID of the type of events to listen for, as these events use
custom interfaces and not a dispatch implementation.
Before shutting down the application, you will need to call
IEventsListenerHelper->UnadviseEvents, then IEventsListenerHelper->Shutdown.
Remember to delete any associated global variables, such as the instance of your
class, and to set any global interface pointers to 0.
• The listener class IDs of the other events will be in the form:
CLSID_Listener
For example, to listen for ActiveViewEvents, use
CLSID_ActiveViewEventsListener as the class ID.
• Inherit from the ArcObjects interface that implements the events—
IActiveViewEvents, for example.
Example
// Set up event listening
// ActiveViewEvents is a custom class that inherits from IActiveViewEvents
// g_activeviewEvents is a global ActiveViewEvents*
// g_ipActViewEventHelper is a global IEventListenerHelperPtr
// g_ipMapControl is a global IMapControl2Ptr
g_activeviewEvents = new ActiveViewEvents();
g_ipActViewEventHelper.CreateInstance(CLSID_ActiveViewEventsListener);
g_ipActViewEventHelper->Startup(static_cast
(g_activeviewEvents));
CComBSTR bsGUID;
::StringFromIID(IID_IActiveViewEvents, &bsGUID);
IUIDPtr ipUID(CLSID_UID);
ipUID->put_Value(CComVariant(bsGUID));
IActiveViewPtr ipActiveView;
g_ipMapControl->get_ActiveView(&ipActiveView);
g_ipActViewEventHelper->AdviseEvents(ipActiveView, ipUID);
...
// You will need to clean up the events. This is done when the application
is given the signal to close.
g_ipActViewEventHelper->UnadviseEvents();
g_ipActViewEventHelper->Shutdown();
g_ipActViewEventHelper = 0;
delete activeviewEvents;
// Shut down application with IAoInitialize's Shutdown
Chapter 4 • Developer environments • 249