Number characters and punctuation characters. You will be seeing many of these in the KeyPress, KeyDown, and KeyUpĪn ASCII code is a number assigned, by formal convention, to each letter in theĪlphabet (separate numbers exist for uppercase and lowercase letters) as well as If having a parameter attached to an event handler is new to you, take a minute to KeyAscii argument and thus makes it available to the event procedure for use. Is fired, Visual Basic passes the ASCII code of the character being input to the KeyPress is associated with the character of the key being pressed. KeyPress.vbp on the Web site devoted to this book. YouĬan test which keys work with this event by using the sample program in the project Only numeric, alphabetic, and select command keys generate a KeyPress event.
Private denotes the scope of the event.Private Sub ControlName_KeyPress( KeyAscii as Integer)
The form with the focus and then to the control with the focus. When users press a key within your program, Windows fires a KeyPress event to Most Visual Basic controls support three keyboard input events-KeyPress(), KeyUp(),Īnd KeyDown()-and five mouse events-(Click(), DblClick(), MouseUp(), MouseDown(), Independence of Windows frees VB programmers from the difficult task of writing code Independence enables you to treat hardware devices as nothing more than event generators.
Operation system and the specific device drivers installed on the system. What particularīrand of input device is attached to a computer is the responsibility of the Windows The same is true for the keyboard and mouse. Programmers code for a printer in general, notĪ specific model of printer. Type of hardware connected to a given system all they know is that a particularĬategory of hardware is out there. In other words, programmers never know the exact This separation-or abstraction,Īs it's called in object-oriented programming-enables programmers to work with generalĬategories of hardware devices from which they can accept data and to which theyĬan send data (see Figure 15.1). Mouse, monitor, and printer from the application programs. System separates independent operating-system hardware (devices) such as the keyboard, Windows is a device-independent operating system. The presence of this distinct architecture elementĭemonstrates the distinct support for device independence in the current Microsoft In the Windows NT operating system, one part of the Executive Services is the Recognizing VB's Limitations with Mouse Input.Working with MouseDown and MouseUp Events.Working with the KeyUp and KeyDown Events.Using Visual Basic 6 - Ch 15 - Handling Keyboard and Mouse Input in Your Programs
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