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Project 3
Multiple Forms,
Dialogs, Debugging,
and EXEs

New Concepts Project 3

• Dialog boxes - used to ask for and supply information
• Debug Window - will be used to find errors in the code when program run
• Executable (stand-alone) applications - run independently from the software that was used to create them
• Visual Basic’s library of built-in financial functions used

SavU Loan Analyzer

• Project calculates amount of monthly payment on a loan.
• Icon consists of a house and car. 
• Inputs - amount of loan (uses text box), length in years, interest rate per year (uses scroll bars)

Run-Time Characteristics

• Dialog box - used to display input error (not a valid numeric amount)
• Clear Button - erases loan amount, monthly payment, and sum of payments and returns scroll bars to their lowest values
• About Button - displays a dialog box with icon, program name, programmer’s name, and date

SavU Loan Analyzer
System Menu

• Opened by clicking the System menu (Control-box) icon
• application can be minimized on desktop by clicking Minimize on System menu or by clicking the application’s Minimize button 
• Close application by choosing Close on System menu or clicking close button 

About... Form Controls

Build the About... form as follows:

• set the size of the form
• add the controls
• set the properties of the form and its controls
• save the form as a file on diskette

Setting Size of Form

• Height property - changes height of form
• Width property - changes width of form

Note: Code can be used at run-time to change the form’s size by changing the values (twips) of these properties

• Top property - position of top of form on desktop
• Left property - position of left side of form on desktop
• StartUpPosition property - determines where a form first displays on desktop at run-time

Image Control

• Image control can be used as a container for graphical images such as icons or bit mapped graphics files. (.bmp extensions)
• Image control acts like a command button, so it often is used to create custom buttons like those found in toolbars.

Line Control

• line control is used to add straight lines between pairs of points on a form

Note: used to visually separate parts of a form (makes the user interface easier to understand)

Properties About... Form

• WindowState of form
• BorderStyle of form
• Font property of controls
• Picture property of Image control
• BorderWidth property of line control

WindowState Property

• WindowState is a property of a form determines window’s size on desktop at run-time.

Run-time WindowState changes

Note: You can control the ability to make run-time changes to the WindowState by including or removing minimize or maximize buttons from the form.

• MinButton property - value is True if it is to be included on the form, False if not
• MaxButton property - value is True if it is to be included on the form, False if not
• ControlBox property - value is True if it is to be included on the form, False setting removes the System menu icon and the Minimize, Maximize, and Close buttons

BorderStyle Property Form

• BorderStyle Property - determines the ability to change the size of a window at run-time by dragging its borders
• affects the form’s appearance and controls
• sizable form has borders that can be dragged to new positions.
• ShowInTaskbar property - determines whether a Form object displays on Windows 95 taskbar

BorderStyle Property Values

 

Note: If BorderStyle is set to none , fixed-dialog, fixed ToolWindow, or Sizable ToolWindow the MinButton, MaxButton, and ShowInTaskbar properties are set automatically to False

Control Names and Captions

Note: Important to name forms, especially in projects that contain more than one form.

Difference between Name and Caption

• Name - is the unique identifier of control or form used by Visual Basic (cmdEnter) (Coding)

• Caption - is the label attached to a control or form on the user interface (Enter)

Font Properties

• Font dialog box - used at design-time to change fonts, font size, and font style for text and data fields (Table 3-3 VB 3.17)
• font characteristics can be changed at run-time using code statements

Note: Font names available are only those installed in Windows on the current PC.

Picture Property
Image Control

• Picture property - setting this property allows you to add graphics to forms and controls at design time.

Note: Visual Basic Package comes with a set of icon files (.ICO) (choose picture property, double-click graphics subdirectory, choose icon subdirectory)

• .frx extension - form containing graphical data is saved using this extension

Picture and BorderStyle Properties
Image Control

• If BorderStyle = 0-None - size of image control adjusted to size of icon
• If BorderStyle = 1-Fixed single - Visual Basic does not adjust its size automatically

Note: Setting BorderStyle to Fixed and the Stretch property to True will cause the icon to be elongated to fill the size of an image control

BorderStyle Line Control

SavU Loan Analyzer Form (steps)

• add a new form to project
• set the size of the form
• add the controls
• set the properties of the form and controls
• save the form as a file on diskette

Adding Shape Controls

• Shape controls - used to group related controls visually
• Inputs - data needed by application to carry out its function (input controls grouped within shape control)
• Outputs - controls related to the results of the application’s function (output controls grouped within shape control)

Coping Controls
Keyboard Commands

• CTRL+C - copies selected control to the Clipboard
• CTRL+V - pastes the control from the Clipboard to the form

  Note: Important to set all the properties of the control before the copy so that all these properties can be copied with the control

Adding Scroll Bar Controls

• Scroll bars - used to view contents of a control when contents cannot fit within the control’s borders.

Note: another use of scroll bar is to give a value to an input

• advantage: prevents you from entering an improper value by mistake. (sets valid range)

2 Kinds of Scroll Bars

• horizontal and vertical in Toolbox Window

Scroll Bar Change Event

• Change event is triggered when you click a scroll arrow or drag the scroll box
• Code statements can be written linking code to the change event that can change the characteristics of other controls tied to the scroll bar such as a caption of a label

Setting Properties

• Loan Payment Form and Controls
• Alignment property of text boxes and labels
• Min and Max properties of Scroll bars
• SmallChange and LargeChange properties of scroll bars
• Icon property of forms

Alignment Property
Text Boxes and Labels

• Specifies where caption will appear will appear within the borders of a control
  • 0-Left Justify (default)
  • 1-Right Justify (double-click)
  • 2-Center

Note: to change text box’s alignment, the value of its MultiLine property must be equal to True (No longer true in VB6)

Scroll Bar Properties

• Value property - integer number that changes in relation to the position of the scroll box within the scroll bar.
• Max property - highest number of value property allowed
• Min property - lowest number of value property allowed

Scroll Bar Properties

• SmallChange property - amount that the value changes each time you click one of the scroll arrows
• LargeChange property - amount that the value changes each time you click the area between the scroll box and the two scroll arrows

Icon Property of Forms

• Icon property - used to specify the graphical image (icon) used to represent the form when it is minimized on the desktop
• Visual Basic contains a set of icons (.ICO files) that are in the COMMON\GRAPHICS\ICON subdirectories

Writing Code

• Code written one event at a time
• See TABLE 3-6 VB 3.42 for a summary of each of the LOAN PAYMENT APPLICATION EVENT PROCEDURES

Start Up Form

• Start Up form - is the first form in a project loaded into computer’s memory and added to the desktop at run-time.

Note: By default, the Start Up Form is the first form created in a project

Note: In Projects 1 and 2, Start Up Form not specified explicitly because they only contained one form which is automatically set as the Start Up Form

hsbYears_Change and Scroll Events

• Change event triggered for scroll bar any time the control’s scroll box is moved by clicking a scroll arrow, dragging the scroll box, or clicking the space between the scroll box and scroll arrow.
  • Each of these movements changes Value property of scroll bar
• Scroll event - occurs when scroll box dragged
• Movement of the scroll box must be linked to a new number displayed in the caption of the label located above the scroll bar

lblYears.Caption = hsbYears.Value

hsbRate_Change and Scroll Events

• Interest rate displayed as the caption of lblRate must be converted from value of hsbRate by multiplying it by .01

Note: This conversion must be done in the code rather than the properties setting section because the Max, Min, SmallChange and LargeChange values can only be set to integer (whole) values

Note: Code copied from the Change to Scroll Event

lblRate.Caption = hsbRate.Value * .01

cmdCalculate_Click Subroutine

• Pmt function - returns the payment for a loan based on periodic, constant payments and a constant interest rate
• Function used in Code statement:

Pmt (rate, nper,pv,fv,due)

• Arguments - entries within the parentheses, input values needed by the function in order to return a value

Error Trapping

• IsNumeric function: - will return a True value if the contents are a number and a False value if the contents are not a valid number
• (FIGURE 3-77 VB 3.48)

Example:

IsNumeric(txtAmount.text)

If... Then block

(FIGURE 3-78 VB 3.49)

Extension if Single-line If Statement

IF condition THEN

statement1
statement2

ELSE

statement3
statement4

ENDIF

3 Parts of Message Box

• used to add dialog box to application

MsgBox text,type,title

• text body of message box(enclosed in quotes)
• type number represents type of button, type of icon, whether dialog box is modal
• title text that appears in title bar (enclosed in quotes)

Online Help - combinations of buttons, icons, and modality (Table 3-9 VB 3.49)

SetFocus Method

• SetFocus method is used to place the cursor back in a control to give it the focus at run-time by using code

Syntax:

controlname.Setfocus

cmdAbout_Click Event

• modal - cannot work with any other window until the dialog box is closed
• forces user to respond to dialog box
• modeless - forms without this property

Note: you make forms visible on the desktop and control their modality at run time with the Show method in a code statement

Form.Show statement

• General format: form.SHOW style
• ARGUMENTS OF SHOW STATEMENT

Note: If style value not included (modeless)

• Unload Statement - used at run-time to remove forms from memory and the desktop (Unload formname)

Form_Load Event

• Form’s Load Event - causes code statements to be carried out when the form is loaded into memory at run-time.
• Will use frmLoanabt’s Load event to assign captions of labels in the About… dialog box

Line Continuation

• Line-continuation character - combination of a space followed by an underscore ( _) used in the development environment to extend a single logical line of code to two or more physical lines
  • has no effect on execution of code
  • makes code much easier to read and understand
  • cannot use within a string expression
  • cannot continue one statement into more than 10 lines

Debugging Applications

• Bug - error in code
• Debugging - process of removing errors
• Immediate window - opens when you run program can be used to debug program
  • allows you to test code statements without changing any of your procedures
• Break button - temporarily halt execution of program (Standard Toolbar)
• Continue button - resumes execution of halted program (Standard Toolbar)

Debugging features

1. Viewing values of variables and properties
    (setting and viewing watch expressions)

2. Halting execution at a particular point
    (setting a breakpoint)

3. Executing code one line at a time
    (stepping through the code)

4. Executing code immediately
    (the Immediate window)

Setting and Viewing Watch Expressions

• Break mode - can isolate and view values of particular variables and properties
• Watch expressions - set to specify which variables and properties to monitor
• Immediate watch - used to check the value of any variable or property in break mode
• Breakpoint - point at which you want to break execution of program

Making Executable Files

• To run an application outside of Visual Basic programming system, you must compile, or convert, the application into an executable, or .exe, file
• Several advanced options are available in the Project Properties window on the Compile tab sheet

Project 3
Multiple Forms,
Dialogs, Debugging,
and EXEs
END

Program Future Value Calculator Requirements

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