Microsoft Visual Basic 2005: Reloaded Second Edition

Microsoft Visual Basic 2005: Reloaded Second Edition Chapter 5 Repeating Program Instructions

Objectives After studying this chapter, you should be able to: • Include the repetition structure in pseudocode and in a flowchart • Write a For...Next statement • Calculate a periodic payment using the Financial.Pmt method • Include a list box and a combo box in an interface • Write a Do...Loop statement Microsoft Visual Basic 2005: Reloaded, Second Edition

Objectives (continued) • Initialize and update counters and accumulators • Display a dialog box using the InputBox function • Create a multiline text box that cannot be edited • Animate a control by moving it across a form • Have the computer sound a beep Microsoft Visual Basic 2005: Reloaded, Second Edition

The Repetition Structure • Repetition structure (or loop): a structure that repeatedly processes one or more program instructions until a condition is met • Pretest loop • The condition is evaluated before the instructions within the loop are processed • The instructions may be processed 0 or more times • Posttest loop • The condition is evaluated after the instructions within the loop are processed • The instructions are always processed at least once Microsoft Visual Basic 2005: Reloaded, Second Edition

The Repetition Structure (continued) • Repetition statements in Visual Basic • For...Next • Do...Loop • For Each...Next Microsoft Visual Basic 2005: Reloaded, Second Edition

The For...Next Statement • For...Next statement • Processes a set of instructions a known number of times • Is a pretest loop Microsoft Visual Basic 2005: Reloaded, Second Edition

The For...Next Statement (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The For...Next Statement (continued) • Startvalue, endvalue, and stepvalue items • Control the number of times the loop is processed • Must evaluate to numeric values • Can be positive or negative • A negative stepvalue causes the loop counter to count down • Flowchart symbol for the For...Next loop is a hexagon Microsoft Visual Basic 2005: Reloaded, Second Edition

The For...Next Statement (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The Financial.Pmt Method • Financial.Pmt method • Calculates a periodic payment on a loan or investment • Returns the periodic payment as a Double type value • Rate and number of periods arguments must be expressed in the same units (monthly, annual, etc.) • Also calculates the amount that must be saved each period to accumulate a specific sum Microsoft Visual Basic 2005: Reloaded, Second Edition

The Financial.Pmt Method (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The Monthly Payment Calculator Application Microsoft Visual Basic 2005: Reloaded, Second Edition

The Monthly Payment Calculator Application (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Selecting the Existing Text in a Text Box • Windows standard: highlight the existing text when a text box receives the focus • SelectAll method: selects all text in a text box • Enter event: occurs when the text box receives the focus Microsoft Visual Basic 2005: Reloaded, Second Edition

Selecting the Existing Text in a Text Box (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Coding a Control’s TextChanged Event Procedure • TextChanged event • Occurs when a change is made in a control’s Text property • Change may be made by user or the program Microsoft Visual Basic 2005: Reloaded, Second Edition

Coding a Control’s TextChanged Event Procedure (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a List Box in an Interface • ListBox tool: creates a ListBox control • ListBox control: displays a list of choices from which the user can select 0 or more choices • SelectionModeproperty: controls the number of choices a user can select • None: user can scroll but not select anything • One: user can select one item • MultiSimple and MultiExtended: user can select multiple items Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a List Box in an Interface (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Adding Items to a List Box • Items collection: a collection of the items in a list box • Collection: a group of one or more individual objects treated as one unit • Index: • A unique number that identifies an item in a collection • Is zero-relative: the first item has index of 0 • Add method: adds an item to the list box’s Items collection Microsoft Visual Basic 2005: Reloaded, Second Edition

Adding Items to a List Box (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Adding Items to a List Box (continued) • Sorted property: • Determines if the list box items are sorted • Sort order is dictionary order Microsoft Visual Basic 2005: Reloaded, Second Edition

Adding Items to a List Box (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The SelectedItem and SelectedIndex Properties • SelectedItem property: • Contains the value of the selected item in the list • If nothing is selected, it contains the empty string • SelectedIndex property: • Contains the index of the selected item in the list • If nothing is selected, it contains the value -1 • Default list box item: the item that is selected by default when the interface first appears Microsoft Visual Basic 2005: Reloaded, Second Edition

The SelectedItem and SelectedIndex Properties (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The SelectedValueChanged and SelectedIndexChanged Events • SelectedValueChanged and SelectedIndexChanged events: occur when a user selects an item in a list box Microsoft Visual Basic 2005: Reloaded, Second Edition

The SelectedValueChanged and SelectedIndexChanged Events (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Modifying the Monthly Payment Calculator Application Microsoft Visual Basic 2005: Reloaded, Second Edition

Modifying the Monthly Payment Calculator Application (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a Combo Box in an Interface • ComboBox tool: creates a combo box control • ComboBox control: • Similar to a list box • May contain a text field that allows the user to type an entry that is not on the list • List portion may be hidden • Three styles of combo boxes: • Simple • DropDown • DropDownList Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a Combo Box in an Interface (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a Combo Box in an Interface (continued) • SelectedItem property: contains the value of the selected item in the list • Text property: contains the value that appears in the text portion of the control (item selected or typed in) Microsoft Visual Basic 2005: Reloaded, Second Edition

Using a Combo Box in an Interface (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

The Do...Loop Statement • Do...Loop statement: codes both a pretest or a posttest loop • Use While or Until to code the condition for the loop • Repetition symbol in a flowchart is the diamond Microsoft Visual Basic 2005: Reloaded, Second Edition

Microsoft Visual Basic 2005: Reloaded Second Edition