ArcGIS Engine Developer Guide

BUILDING APPLICATIONS WITH THE ARCGIS CONTROLS
For step-by-step scenarios walking you through
the ArcGIS controls development process, refer to
the ‘Building applications’ scenario of your choice
in Chapter 6, ‘Developer scenarios’.
The ArcGIS controls can be used to build applications in two ways: the ArcGIS
controls can be embedded into an existing application to add additional mapping
capability, or the ArcGIS controls can be used to create a new standalone application.
In either case, an individual ArcGIS control can be embedded into an application
or the TOCControl and ToolbarControl can be used in conjunction with
another ArcGIS control to provide part of the application’s framework. The
following sections discuss the application development process for the controls
both when you are utilizing the ToolbarControl and when you choose not to.
APPLICATION DEVELOPMENT USING THE TOOLBARCONTROL
The ToolbarControl is typically used in conjunction with a buddy control and a
selection of the control commands to quickly provide a functional GIS application.
The ToolbarControl is not only providing a part of the user interface; it is also
providing a part of the application’s framework. ArcGIS Desktop applications,
such as ArcMap, ArcGlobe, and ArcScene, have a powerful and flexible framework
that includes user interface components such as toolbars, commands,
menus, dockable windows, and status bars. This framework enables the end user
to customize the application by allowing them to reposition, add, and remove
most of these user interface components.
Many development environments provide some pieces of a framework in the
form of simple dialog boxes, forms, and multiple docking interface (MDI) applications.
They also provide generic user interface components such as buttons,
status bars, and list boxes. However, a substantial amount of coding can still be
required to provide toolbars and menus that host commands, especially if they
need to be customized by the end user.
The ToolbarControl and the objects within its library can supply pieces of a framework
similar to the ArcGIS Desktop application framework. You can use some or
all of these framework pieces when building an application with the
ToolbarControl.
Commands
ArcGIS Engine provides several suites of control commands that work with the
ArcGIS controls to perform some specific action. You can extend this suite of
control commands by creating their own customized commands that perform
some specific piece of work. All of these command objects implement the
ICommand interface that is used by the ToolbarControl to call methods and access
properties at appropriate times.
The ICommand::OnCreate method is called shortly after the Command object is
hosted on the ToolbarControl. The method is passed a handle or “hook” to the
application with which the command will work. The implementation of a command
normally tests to see if the hook object is supported (that is, the command
tests to see that the hook is an object that the command can work with). If the
hook is not supported, the command disables itself. If the hook is supported, the
command stores the hook for later use. For example, if an Open Map Document
command is to work with the MapControl or PageLayoutControl, and they are passed
to the OnCreate method as the hook, the command will store the hook for later
use. If the ToolbarControl is passed to the OnCreate event as the hook, the command
would normally check the type of buddy control being used in conjunction
50 • ArcGIS Engine Developer Guide