Access-8.ppt 525KB Mar 29 2010 04:55:16 AM
Exploring Microsoft Access
Chapter 8
Creating More Powerful
Applications:
Introduction to VBA
Objectives (1 of 2)
• Describe relationship of VBA to Microsoft Office
• Describe components of the Module window
• Describe two ways to create an event procedure
• Explain how the Quick Info and Complete Word
features simplify entry of VBA statements
• Create a combo box to locate a record on a form
Objectives (2 of 2)
• Describe MsgBox parameters
• Create an event procedure to facilitate data entry
through keyboard shortcuts
• Create an event procedure that substitutes an
application-specific message for the standard
Access error messages
• Describe several types of data validation
Overview
• VBA is a programming language to build
truly useful Access applications
• VBA is event driven: Procedures respond to
specific events
• VBA can modify procedures that Access
has already created
• Provide an appreciation for what can be
accomplished with VBA
Introduction to VBA
• Data validation
• Facilitate data entry, including creating
keyboard shortcuts
• Error trapping
• Enhance communication with the user by
using message boxes
Modules and Procedures
• Visual Basic code is developed in units called
procedures
• Event procedures: run automatically in
response to an event
• General procedures: called explicitly from
within another procedure
Modules
• All procedures are stored in modules; one module
contains one or more procedures
• Every form in Access has its own module (Class
module), which contains procedures for that form
• Private procedure: accessible only from within the
module in which it is contained
• Public procedure: accessible from anywhere
• Module window: where procedures in a module
are displayed and edited
Module Window
Name of procedure
(Form_Close)
MsgBox
statement
End of
procedure
Name of next
Procedure
(Form_Current)
MsgBox Statement
• MsgBox takes three arguments (known as
parameters)
• Prompt: Specifies the message text
• Buttons: Type of command buttons and icon
• Title: Text that appears in title bar of the
message box
Create an Event Procedure
Right click on
Form Selector
box and choose
Properties
Select Event tab
Click On Current
Select Code Builder
On Current Event Procedure
Procedure header
Name of Combo
Box from step 3
Complete Word will
provide completion
options
Facilitating Data Entry
• Use the Default property to specify default
values for certain fields
• Use VBA to create keyboard shortcuts
• A KeyDown event procedure can
implement keyboard shortcuts
KeyDown Event Procedure
Key words
Appear in blue
Select Form in the
Object list box
Select KeyDown
from the Procedure List box
ShortCut Command Button
Select the command
button Properties
All tab
Change Name to
ShortCutButton
Change Caption to
&ShortCuts
Command Button tool
Error Trapping
• Produce more user-friendly error message
• Find the error number using the Immediate
window
• Use case statements to test the value of an
incoming variable and produce the appropriate
statement
• Once error is detected, Call MsgBox statement
to display your user-friendly error message
• Else will execute if all Case statements fail
Error Event Procedure
Error numbers
Case 1
Case 2
Else statement
Data Validation
• Invalid data corrupts validity of information
• Data validation is therefore crucial
• Use VBA to extend data validation
capabilities within Access
• Use a nested IF statement to remind users to
leave no fields empty
MsgBox Function vs. Statement
• MsgBox function: displays a prompt to
the user, then returns a value
- Requires parentheses around arguments
• MsgBox statement: simply displays a
message, does not use parentheses
Chapter 8 Summary (1 of 2)
• VBA is a subset of Visual Basic
• VBA is accessible by all Microsoft Office
applications
• All VBA procedures are stored in modules
• Every form in Access has its own module that
contains the event procedures for that form
Chapter 8 Summary (2 of 2)
• All procedures are either public or private:
Private—accessible only from within its module
public—accessible from anywhere
• Event procedures were created to illustrate how
VBA is used to improve an application
• MsgBox function has three arguments:
message, intrinsic constant, and title bar message
Chapter 8
Creating More Powerful
Applications:
Introduction to VBA
Objectives (1 of 2)
• Describe relationship of VBA to Microsoft Office
• Describe components of the Module window
• Describe two ways to create an event procedure
• Explain how the Quick Info and Complete Word
features simplify entry of VBA statements
• Create a combo box to locate a record on a form
Objectives (2 of 2)
• Describe MsgBox parameters
• Create an event procedure to facilitate data entry
through keyboard shortcuts
• Create an event procedure that substitutes an
application-specific message for the standard
Access error messages
• Describe several types of data validation
Overview
• VBA is a programming language to build
truly useful Access applications
• VBA is event driven: Procedures respond to
specific events
• VBA can modify procedures that Access
has already created
• Provide an appreciation for what can be
accomplished with VBA
Introduction to VBA
• Data validation
• Facilitate data entry, including creating
keyboard shortcuts
• Error trapping
• Enhance communication with the user by
using message boxes
Modules and Procedures
• Visual Basic code is developed in units called
procedures
• Event procedures: run automatically in
response to an event
• General procedures: called explicitly from
within another procedure
Modules
• All procedures are stored in modules; one module
contains one or more procedures
• Every form in Access has its own module (Class
module), which contains procedures for that form
• Private procedure: accessible only from within the
module in which it is contained
• Public procedure: accessible from anywhere
• Module window: where procedures in a module
are displayed and edited
Module Window
Name of procedure
(Form_Close)
MsgBox
statement
End of
procedure
Name of next
Procedure
(Form_Current)
MsgBox Statement
• MsgBox takes three arguments (known as
parameters)
• Prompt: Specifies the message text
• Buttons: Type of command buttons and icon
• Title: Text that appears in title bar of the
message box
Create an Event Procedure
Right click on
Form Selector
box and choose
Properties
Select Event tab
Click On Current
Select Code Builder
On Current Event Procedure
Procedure header
Name of Combo
Box from step 3
Complete Word will
provide completion
options
Facilitating Data Entry
• Use the Default property to specify default
values for certain fields
• Use VBA to create keyboard shortcuts
• A KeyDown event procedure can
implement keyboard shortcuts
KeyDown Event Procedure
Key words
Appear in blue
Select Form in the
Object list box
Select KeyDown
from the Procedure List box
ShortCut Command Button
Select the command
button Properties
All tab
Change Name to
ShortCutButton
Change Caption to
&ShortCuts
Command Button tool
Error Trapping
• Produce more user-friendly error message
• Find the error number using the Immediate
window
• Use case statements to test the value of an
incoming variable and produce the appropriate
statement
• Once error is detected, Call MsgBox statement
to display your user-friendly error message
• Else will execute if all Case statements fail
Error Event Procedure
Error numbers
Case 1
Case 2
Else statement
Data Validation
• Invalid data corrupts validity of information
• Data validation is therefore crucial
• Use VBA to extend data validation
capabilities within Access
• Use a nested IF statement to remind users to
leave no fields empty
MsgBox Function vs. Statement
• MsgBox function: displays a prompt to
the user, then returns a value
- Requires parentheses around arguments
• MsgBox statement: simply displays a
message, does not use parentheses
Chapter 8 Summary (1 of 2)
• VBA is a subset of Visual Basic
• VBA is accessible by all Microsoft Office
applications
• All VBA procedures are stored in modules
• Every form in Access has its own module that
contains the event procedures for that form
Chapter 8 Summary (2 of 2)
• All procedures are either public or private:
Private—accessible only from within its module
public—accessible from anywhere
• Event procedures were created to illustrate how
VBA is used to improve an application
• MsgBox function has three arguments:
message, intrinsic constant, and title bar message