Visual Basic.NET How to Program (PDF)

Chapter 16 Graphics and Multimedia 731
The Windows Media Player control provides several buttons that allow the user to play
the current file, pause, stop, play the previous file, rewind, forward and play the next file.
The control also includes a volume control and trackbars to select a specific position in the
media file.
The application provides a MainMenu, which includes File and About menus. The
File menu contains the Open and Exit menu items; the About menu contains the About
Windows Media Player menu item.
When a user chooses Open from the File menu, the openMenuItem_Click event
handler (lines 22–36) executes. An OpenFileDialog box displays (line 25), allowing
the user to select a file. The program then sets the FileName property of the player (the
Windows Media Player control object of type AxMediaPlayer) to the name of the file
chosen by the user. The FileName property specifies the file that Windows Media Player
currently is using. Lines 31–35 adjust the size of player and the application to reflect the
size of the media contained in the file.
The event handler that executes when the user selects Exit from the File menu (lines
39–43) simply calls Application.Exit to terminate the application. The event handler
that executes when the user chooses About Windows Media Player from the
About menu (lines 46–51) calls the AboutBox method of the player. AboutBox simply
displays a preset message box containing information about Windows Media Player.
16.13 Microsoft Agent
Microsoft Agent is a technology used to add interactive animated characters to Windows
applications or Web pages. Interactivity is the key function of Microsoft Agent technology:
Microsoft Agent characters can speak and respond to user input via speech recognition and
synthesis. Microsoft employs its Agent technology in applications such as Word, Excel and
PowerPoint. Agents in these programs aid users in finding answers to questions and in understanding
how the applications function.
The Microsoft Agent control provides programmers with access to four predefined
characters—Genie (a genie), Merlin (a wizard), Peedy (a parrot) and Robby (a robot). Each
character has a unique set of animations that programmers can use in their applications to
illustrate different points and functions. For instance, the Peedy character-animation set
includes different flying animations, which the programmer might use to move Peedy on
the screen. Microsoft provides basic information on Agent technology at its Web site:
www.microsoft.com/msagent
Microsoft Agent technology enables users to interact with applications and Web pages
through speech, the most natural form of human communication. When the user speaks into
a microphone, the control uses a speech recognition engine, an application that translates
vocal sound input from a microphone into language that the computer understands. The
Microsoft Agent control also uses a text-to-speech engine, which generates characters’
spoken responses. A text-to-speech engine is an application that translates typed words into
audio sound that users hear through headphones or speakers connected to a computer.
Microsoft provides speech recognition and text-to-speech engines for several languages at
its Web site:
www.microsoft.com/products/msagent/downloads.htm