Tutorial 6 1

List Box Control

Can be used to display a set of choices

from which the user can select only one

You also can create multi-selection list

boxes from which the user can select

zero or more choices (See Lesson A’s

Discovery Exercise 11)

Tutorial 6 2

GUI Standards for List Boxes

List boxes should contain a minimum of three selections

You should display a minimum of three selections and a maximum of eight selections at a time

Use a label control to provide keyboard access to the list box

Tutorial 6 3

AddItem Method

Used to add items to a list box

Syntax

control.AddItem item

item is the expression you want displayed, and it can be either numeric or string

if item is a literal string constant, then it must be enclosed in quotation marks

Tutorial 6 4

Arrangement of List Box Items

By use, with the most used entries

appearing first in the list

Sorted in ascending order either

alphabetically, numerically, or

chronologically

Tutorial 6 5

Sorted Property

Can be set to either the Boolean value True or the Boolean value False

If set the True, the list box items will be sorted in ascending order

If set to False, the list box items will appear in the order in which they were entered

Tutorial 6 6

ListIndex Property

You can use the ListIndex property to refer to an item in the list box

The first item in a list box has a ListIndex value of 0

If no items are selected in the list box, the ListIndex property has a value of -1

Tutorial 6 7

Default Item

It is customary to select a default item in a single-selection list box when the interface first appears

The default item should be either the most used selection or the first selection in the list

lstName.ListIndex = 0 will select the first item in the lstName list box

A default selection typically is not made in a multi-selection list box

Tutorial 6 8

Program Files vs Data Files

A program file contains the instructions

that both create the user interface and

tell the objects how to respond to events

A data file is a collection of information

composed of fields and records

Tutorial 6 9

Fields, Records, and Data Files

A field is a single item of information about a person, place, or thing

A record is a group of related fields that contain all of the necessary data about a specific person, place, or thing

A data file is a collection of related records

Tutorial 6 10

Sequential Access Data Files

Similar to a cassette tape in that each record in the file is both stored and retrieved in consecutive order

Advantage: easy to create

Disadvantage: you can process the records only in the order in which they were entered

Use for small files, files consisting only of text, or files that will always be accessed in sequential order

Tutorial 6 11

Open Statement

Open pathname For mode As # filenumber

pathname is the name of the file you want to open; it should include the drive letter and path, and it must be enclosed in quotation marks (unless it is stored in a String variable

mode can be either Input, Output, or Append

filenumber is a number that you assign to the file, and it must be an integer between 1 and 511, inclusive

Tutorial 6 12

Sequential Access File Modes

Input - you open a file for Input when you want to read the file

Output - you open a file for Output when you want to create a new file and then write data to it

Append - you open a file for Append when you want to add data to the end of an existing file

Tutorial 6 13

Record Pointer

When you open a file for Input, the record pointer is positioned at the beginning of the file, immediately before the first record

When you open a file for Output, the record pointer is positioned at the beginning of the empty file

When you open a file for Append, the record pointer is positioned immediately after the last record in the file

Tutorial 6 14

Write # Statement

Write # filenumber, [outputlist]

filenumber is the number used in the Open statement to open the file

outputlist is one or more numeric or string expressions, separated by commas

Tutorial 6 15

Close Statement

Close [# filenumber]

filenumber is the number used in the Open statement to open the file

A Close statement with no filenumber closes all open files

Tutorial 6 16

Verifying the Contents of a Sequential Access File

Use a basic word processor or text editor

Each line in the sequential access file represents a record

Fields in the record are separated by commas

String fields are enclosed in quotation marks

Tutorial 6 17

Sequential Access File

Tutorial 6 18

EOF Function

EOF(filenumber)

filenumber is the number used in the Open statement to open the file

EOF stands for “end of file”

returns the Boolean value True if the record pointer is at the end of the file (after the last record); otherwise it returns the Boolean value False

Do While Not EOF(1)

Do Until EOF(1)

Tutorial 6 19

Input # StatementInput # filenumber, variablelist

filenumber is the number used in the Open statement to open the file

variablelist is one or more numeric or string variables, separated by commas

Each variable in the variablelist is associated with a field in the record

The number, data type, and order of the variables in the variablelist must match the fields in the record

Tutorial 6 20

Print Method

Print [outputlist] - prints to the form

Printer.Print [outputlist] prints to the printer

Printer is a keyword that refers to the Printer object

Outputlist is the expression or list of expressions you want to print; if outputlist is omitted, the Print method prints a blank line

Tutorial 6 21

Print Method SeparatorsComma - tells Visual Basic to tab to the next print zone before printing the next character

Semicolon - tells Visual Basic to move to the next print position before printing the next character

You also can use the spacebar in place of the semicolon

Tutorial 6 22

Printing Strings and NumbersWhen you print a string literal constant, Visual Basic prints only the characters included within the quotation marks

Visual Basic prints positive numbers with both a leading and a trailing space

Visual Basic prints negative numbers with a leading minus sign and a trailing space

Tutorial 6 23

Spc and Tab Functions

Spc(number)

Number represents the number of spaces to insert before displaying or printing the next item in the outputlist

Tab(number)

Number represents the column number, or print position, to which you want Visual Basic to tab before printing the next item in the outputlist

Tutorial 6 24

Fixed-spaced vs Proportionally-spaced Fonts

Fixed-spaced fonts

Also called monospaced fonts

Use the same amount of space to print each character

Courier New is a fixed-spaced font

Proportionally-spaced fonts

Use varying amounts of space to print characters

MS Sans Serif is a proportionally-spaced font

Tutorial 6 25

Right-justifying and Aligning Numbers by Decimal Point

Use the Format function to ensure that

each number in the column has the

same number of digits to the right of

the decimal point

Use the RSet statement to right-align

the numbers within the column

Tutorial 6 26

Format Function

Format(expression, format)

expression specifies the number, date, time, or string whose appearance you want to format

format is either the name of a predefined Visual Basic format or a string containing special symbols that tell Visual Basic how you want the expression displayed

Tutorial 6 27

RSet Statement

RSet stringvariable = string

stringvariable is the name of a fixed-length String variable

A fixed-length String variable is one whose maximum length is defined when the variable is created

Dim variablename As String * number

string is the expression you want right-aligned

Tutorial 6 28

Printer Spacing ChartReports should have a report title and column headings

Detail lines show the information used to calculate the subtotals and grand total

999 indicates numbers having a maximum of 3 digits

XXX indicates a string having a maximum of 3 characters

Include an “End of report” message

Tutorial 6 29

MultiLine Property

Controls how many lines a text box can both accept and display

Can be set to either True or False (default)

Visual Basic automatically wraps the text in a multiline box if the text extends beyond the size of the box

Tutorial 6 30

ScrollBars Property

Specifies whether a text box has no scroll bars, horizontal scroll bars, vertical scroll bars, or both horizontal and vertical scroll bars

Visual Basic ignores the value in the ScrollBars property unless the MultiLine property is set to True

Tutorial 6 31

Sizing a Control Along with the Form

Set the control’s Height and Width properties to the form’s ScaleHeight and ScaleWidth properties

Enter the sizing code in the form’s Resize event, which occurs when the form is first displayed on the screen and when the user changes the size of the form either by minimizing, maximizing, or restoring it, or by using the form’s borders to resize it

Tutorial 6 32

Menus

Created in the Menu Editor

Can contain menu titles, menu items, separator bars, submenu titles, and submenu items

To avoid confusion, it is best to use one level of menus

Tutorial 6 33

Menu Elements in User Interface

Tutorial 6 34

Menu Elements in Menu Editor

Tutorial 6 35

Access Keys

Assign to each menu title and each menu item

Must be unique within a menu

Menu titles are accessed by pressing the Alt key and the access key

Menu items are accessed by pressing the access key when the menu is open

Tutorial 6 36

Shortcut Keys

Assign to commonly used menu commands

Displayed to the right of the menu item

Can be used only when the menu is closed

Tutorial 6 37

More on Menu Controls

You must provide a name and a caption for each menu control

Each menu title and each menu item is considered a separate control and it can have its own code

A menu control can recognize only the Click event

Tutorial 6 38

Separator Bar

A separator bar is a horizontal line used

to separate two groups of menu items

Created by entering a hyphen in the

menu control’s Caption property

Even separator bars must have a name

Tutorial 6 39

Clipboard Object

Provides access to the Windows

clipboard

Allows you to include cut, copy, and

paste capabilities in your application

Tutorial 6 40

Methods of the Clipboard Object

SetText methodsends text to the clipboard

Clipboard.SetText data

GetText() methodretrieves text from the clipboard

Clipboard.GetText()

Clear methodclears the contents of the clipboard

object.Clear

Tutorial 6 41

SelText Property

When a user selects text in a text box, Visual Basic records the text in the text box’s SelText property

This property contains a zero-length string if no text is selected

You also can use the SelLength property to determine if any text is selected in the text box

Tutorial 6 42

Clipboard.SetText “Have a nice day” Places the string “Have a niceday” on the clipboard

Clipboard.SetText txtEdit.Text Places a copy of the txtEditcontrol’s contents on theclipboard

Clipboard.SetText txtEdit.SelText Places a copy of the textcurrently selected in the txtEditcontrol on the clipboard

txtEdit.Text = Clipboard.GetText() Retrieves the text from theclipboard and places a copy of itin the txtEdit control, replacingthe existing text

txtEdit.SelText = Clipboard.GetText() Retrieves the text from theclipboard and places a copy of itin the txtEdit control, replacingonly the selected text

txtEdit.SelText = “” Removes the selected text fromthe txtEdit control

Clipboard.Clear Clears the contents of theclipboard

Tutorial 6 43

Edit Menu Click Event

Tutorial 6 44

Copy Command Click Event

Tutorial 6 45

Cut Command Click Event

Tutorial 6 46

Paste Command Click Event

Tutorial 6 47

String Manipulation Functions

Left(string, length)

returns the leftmost length characters in the string

Right(string, length)

returns the rightmost length characters in the string

Mid(string, start[, length])

returns length characters from string, beginning with start

Tutorial 6 48

Instr Function

Instr(start, string1, string2[,compare]start is a numeric expression that sets the starting position for the search

string1 is the string expression being searched

string2 is the string expression being sought

compare is either 0 (default; case-sensitive) or 1 (case-insensitive)

returns the starting position of string2 within string1

Tutorial 6 49

Debugging Technique

Visual Basic’s Edit menu provides two

commands that you can use to edit the

code in an application quickly. These

commands are Find and Replace