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Programming with Microsoft Visual Basic 2008 Fourth Edition

Programming with Microsoft Visual Basic 2008 Fourth Edition. Chapter Two Designing Applications. Previewing the Playtime Cellular Application. Playtime Cellular application: Allows salespeople to enter customer’s name, address, and number of blue and pink phones ordered

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Programming with Microsoft Visual Basic 2008 Fourth Edition

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  1. Programming with Microsoft Visual Basic 2008 Fourth Edition Chapter Two Designing Applications

  2. Previewing the Playtime Cellular Application • Playtime Cellular application: • Allows salespeople to enter customer’s name, address, and number of blue and pink phones ordered • Calculates and displays total number of phones ordered and the total price of the order Programming with Microsoft Visual Basic 2008, Fourth Edition

  3. Previewing the Playtime Cellular Application (continued) Figure 2-2 Completed order form Programming with Microsoft Visual Basic 2008, Fourth Edition

  4. Lesson A Objectives After studying Lesson A, you should be able to: • Plan an object-oriented application in Visual Basic 2008 • Complete a TOE (Task, Object, Event) chart • Follow the Windows standards regarding the layout and labeling of controls Programming with Microsoft Visual Basic 2008, Fourth Edition

  5. Creating an Object-Oriented Application • Developing an application is like building a home • Role of programmer analogous to that of builder • Bugs: Problems that affect application functions Programming with Microsoft Visual Basic 2008, Fourth Edition

  6. Creating an Object-Oriented Application (continued) Figure 2-3: Processes used by a builder and a programmer Programming with Microsoft Visual Basic 2008, Fourth Edition

  7. Planning an Object-Oriented Application • Actively involve user in planning phase • End product should closely match the user’s needs and wants • TOE chart: Used to record tasks, objects, and events required for the application Programming with Microsoft Visual Basic 2008, Fourth Edition

  8. Planning an Object-Oriented Application (continued) Figure 2-4: Steps for planning an OO application Programming with Microsoft Visual Basic 2008, Fourth Edition

  9. Identifying the Application’s Tasks • What information will the application need to display on the screen and/or print on the printer? • What information will the user need to enter into the user interface? • What information will the application need to calculate to produce the desired result? • How will the user end the application? • Will previous information need to be cleared from the screen before new information is entered? Programming with Microsoft Visual Basic 2008, Fourth Edition

  10. Identifying the Application’s Tasks (continued) Figure 2-6: Tasks entered in a TOE chart Programming with Microsoft Visual Basic 2008, Fourth Edition

  11. Identifying the Application’s Tasks (continued) Figure 2-6: Tasks entered in a TOE chart (continued) Programming with Microsoft Visual Basic 2008, Fourth Edition

  12. Identifying the Objects • Assign each task to an object in user interface • Objects to be used: Label control, button control, text box • Label control: Displays information that user should not change • Button control: Performs an action immediately after a click event • Text box: Provides an area for user to enter data Programming with Microsoft Visual Basic 2008, Fourth Edition

  13. Identifying the Events • Determine which event (if any) must occur for an object to do its assigned task • Text boxes: No special event is needed • Label controls: No special event is needed • btnCalc, btnClear, and btnExit buttons: Must perform assigned tasks when clicked Programming with Microsoft Visual Basic 2008, Fourth Edition

  14. Identifying the Events (continued) Figure 2-9: Completed TOE chart ordered by object Programming with Microsoft Visual Basic 2008, Fourth Edition

  15. Drawing a Sketch of the User Interface • Follow Windows standards for designing the interface • In Western countries, information flows either vertically or horizontally • Vertical arrangement: Information flows from top to bottom, with essential information located in first column • Horizontal arrangement: Information flows from left to right, with essential information placed in first row Programming with Microsoft Visual Basic 2008, Fourth Edition

  16. Drawing a Sketch of the User Interface (continued) Figure 2-10: Vertical arrangement of the Playtime Cellular application Programming with Microsoft Visual Basic 2008, Fourth Edition

  17. Drawing a Sketch of the User Interface (continued) Figure 2-11: Horizontal arrangement of the Playtime Cellular application Programming with Microsoft Visual Basic 2008, Fourth Edition

  18. Drawing a Sketch of the User Interface (continued) • White space or containers may be used to group related controls • Containers: Objects used to group related controls • Examples: GroupBox, Panel, TableLayoutPanel • Label controls that display output should have meaningful names • Example: “Total Price” identifies lblTotalPrice label • Identifying labels should end with colon (:) • Example: “Total Price:” Programming with Microsoft Visual Basic 2008, Fourth Edition

  19. Drawing a Sketch of the User Interface (continued) • Sentence capitalization: Only first letter in the first word is capitalized • Use for identifying labels • Book title capitalization: Capitalize first letter of each word except articles, conjunctions, and prepositions • Use for button text • Buttons should be same height and width, and should be aligned • Group related controls together, and keep margins consistent Programming with Microsoft Visual Basic 2008, Fourth Edition

  20. Lesson A Summary • Steps to create an OO application: • Meet with client • Plan application • Build user interface • Code application • Test and debug application • Assemble documentation • To plan OO application, identify tasks, objects and events that are needed • Identify information needed as input to produce desired result Programming with Microsoft Visual Basic 2008, Fourth Edition

  21. Lesson B Objectives After studying Lesson B, you should be able to: • Build the user interface using your TOE chart and sketch • Follow the Windows standards regarding the use of graphics, fonts, and color • Set a control’s BorderStyle property • Add a text box to a form • Lock the controls on the form • Assign access keys to controls • Use the TabIndex property Programming with Microsoft Visual Basic 2008, Fourth Edition

  22. Building the User Interface • Use TOE chart and sketch as guides when building user interface • Place appropriate controls on forms • Set applicable properties of controls • Some features of user interface: • Information is arranged vertically • Controls are aligned and appropriately labeled • Try to create an interface that no one notices Programming with Microsoft Visual Basic 2008, Fourth Edition

  23. Building the User Interface (continued) Figure 2-12: Partially completed interface for the Playtime Cellular application Programming with Microsoft Visual Basic 2008, Fourth Edition

  24. Including Graphics in the Interface • Graphics: Icons or pictures added to an interface • Used to emphasize or clarify a portion of screen, or for aesthetic purposes • The human eye is attracted to pictures before text • Include graphic only if it is necessary • Graphics for aesthetic use should be small and positioned to avoid distracting user Programming with Microsoft Visual Basic 2008, Fourth Edition

  25. Selecting Fonts for the Interface • Font property: Controls font type, style, and size • Recommendations for fonts: • Use sans serif fonts (without strokes) • e.g., Segoe UI, Tahoma, Microsoft Sans Serif • Use 8-12 point size fonts for interface • Use only one or two font sizes and one font type • Avoid italics and underlining • Limit bold text to titles, headings, and key items • Objects added to form inherit form’s font setting Programming with Microsoft Visual Basic 2008, Fourth Edition

  26. Adding Color to the Interface • The eye is drawn to color before black and white • Add color only if there is good reason • Many people have trouble distinguishing color • Guidelines for adding colors: • Use dark text against light background • Limit of three colors • Not including black, white, gray • Colors added should be complementary • Avoid using dark color for background • Use color to help identify interface elements, but not as only means of identification Programming with Microsoft Visual Basic 2008, Fourth Edition

  27. The BorderStyle and AutoSize Properties • BorderStyle property: Determines style of control’s border • None: Ensures control will not have border • FixedSingle: Surrounds control with thin line • Fixed3D: Gives control a 3-D appearance (default) • AutoSize property: Determines whether label control automatically sizes to fit its current contents • Use True for identifying labels, but use False for output labels Programming with Microsoft Visual Basic 2008, Fourth Edition

  28. Adding a Text Box Control to the Form • Text box control • Provides an area in the form for data entry • Use TextBox tool to add a text box control • Make all text boxes same size and align them using snap lines • Blue snap lines: For vertical alignment • Pink snap lines: For horizontal alignment Programming with Microsoft Visual Basic 2008, Fourth Edition

  29. Adding a Text Box Control to the Form (continued) Figure 2-13: Snap lines shown in the interface Programming with Microsoft Visual Basic 2008, Fourth Edition

  30. Locking the Controls on a Form • Lock controls after they are properly placed • Purpose: Avoid inadvertently moving controls • A locked control is identified by a small-lock • To lock controls: • Click form (or any control on the form) • Click Format on menu bar • Click Lock Controls • Follow same procedure to unlock controls Programming with Microsoft Visual Basic 2008, Fourth Edition

  31. Assigning Access Keys • Access key • Enables object to be selected using keyboard • Key combination: Alt key + letter or number • Each access key must be unique • Shown in interface as underlined letter • Assigning an access key: • Include an ampersand (&) in the control’s caption • Example: “&Calculate Order” assigns ‘C’ to button Programming with Microsoft Visual Basic 2008, Fourth Edition

  32. Assigning Access Keys (continued) • Reasons to assign access keys: • Allow user to work even if mouse does not • Allow fast typists to keep hands on the keyboard • Allow people with disabilities that prevent them from using a mouse to be able to use application • Follow Windows standards for assigning commonly used access keys Programming with Microsoft Visual Basic 2008, Fourth Edition

  33. Setting the TabIndex Property • Focus: State in which a control is ready to accept user input or action • Pressing Tab key or access key shifts focus • TabIndex property: Contains number representing order in which control will receive focus when user presses Tab key • Control with TabIndex of 0 receives focus first • Set TabIndex using Properties window or Tab Order option on View menu • Make a list of objects to determine proper ordering Programming with Microsoft Visual Basic 2008, Fourth Edition

  34. Setting the TabIndex Property (continued) Figure 2-15: TabIndex boxes showing the correct TabIndex values Programming with Microsoft Visual Basic 2008, Fourth Edition

  35. Lesson B Summary • To specify control’s border, set BorderStyle property • To lock/unlock controls on form, use Lock Controls option on Format menu • To assign an access key to control, type an ampersand (&) in Text property of control or identifying label • To set tab order, set each control’s TabIndex property to number that represents order in which you want the control to receive focus Programming with Microsoft Visual Basic 2008, Fourth Edition

  36. Lesson C Objectives After studying Lesson C, you should be able to: • Code an application using its TOE chart • Plan an object’s code using pseudocode or a flowchart • Write an assignment statement • Send the focus to a control while an application is running • Include internal documentation in the code • Write arithmetic expressions • Use the Val and Format functions Programming with Microsoft Visual Basic 2008, Fourth Edition

  37. Coding the Application • Code: Instructions added to an application • Coding is done after planning and building interface • TOE charts show which objects and events need to be coded • Playtime Cellular application code requirements: • Three buttons associated with Click events Programming with Microsoft Visual Basic 2008, Fourth Edition

  38. Coding the Application (continued) Figure 2-18: Playtime Cellular application’s interface Programming with Microsoft Visual Basic 2008, Fourth Edition

  39. Coding the Application (continued) Figure 2-19: Playtime Cellular application’s TOE chart (ordered by object) Programming with Microsoft Visual Basic 2008, Fourth Edition

  40. Planning a Procedure Using Pseudocode • Pseudocode: Short phrases used to describe the steps a procedure must take to accomplish its goal • Travel directions are a type of pseudocode • btnCalc Click event procedure: Must calculate total phones ordered and total price, and then display results Programming with Microsoft Visual Basic 2008, Fourth Edition

  41. Planning a Procedure Using Pseudocode (continued) Figure 2-20: Pseudocode for the Playtime Cellular application Programming with Microsoft Visual Basic 2008, Fourth Edition

  42. Planning a Procedure Using a Flowchart • Flowchart: Uses standardized symbols to show program logic • Oval: Start/stop symbol • Rectangle: Process symbol; represents a task • Parallelogram: Input/output symbol • Flowlines: Connect the symbols • Flowcharts depict same logic as pseudocode • Programmers usually use either flowcharts or pseudocode (but not both) Programming with Microsoft Visual Basic 2008, Fourth Edition

  43. Coding the btnClear Control’s Click Event Procedure • btnClear control’s task: Clear screen for next order • String: Group of characters enclosed in quotation marks (“”) • Zero-length string (or empty string): Pair of quotation marks with nothing between them (“”) • Two ways to remove control contents at runtime: • Assign zero-length string to control’s Text property • Assign String.Empty to control’s Text property Programming with Microsoft Visual Basic 2008, Fourth Edition

  44. Coding the btnClear Control’s Click Event Procedure (continued) Figure 2-22: Pseudocode for the btnClear control’s Click event procedure Programming with Microsoft Visual Basic 2008, Fourth Edition

  45. Assigning a Value to a Property During Run Time • Assignment statement: Instruction assigning a value to object at runtime • Syntax: object.property = expression • object and property are object and property names • expression contains the value to be assigned • Assignment operator (=): Assigns value on right side to the object on left side Programming with Microsoft Visual Basic 2008, Fourth Edition

  46. Using the Focus Method • Method: Predefined procedure • Focus method: • Allows you to move focus to specified control • Syntax: object.Focus() • Object: Name of control that receives focus Programming with Microsoft Visual Basic 2008, Fourth Edition

  47. Internally Documenting the Program Code • Comments: Internal documentation in program • Used by programmers to document a procedure’s purpose or explain sections of code • To create comment, place an apostrophe (’) before a statement • Compiler ignores all characters after apostrophe for rest of line • Comments are color-coded in IDE • Comments help make code readable Programming with Microsoft Visual Basic 2008, Fourth Edition

  48. Internally Documenting the Program Code (continued) Figure 2-24: Completed Click event procedure for the btnClear control Programming with Microsoft Visual Basic 2008, Fourth Edition

  49. Internally Documenting the Program Code (continued) Figure 2-25: Comments entered in the General Declarations section Programming with Microsoft Visual Basic 2008, Fourth Edition

  50. Writing Arithmetic Expressions • Arithmetic expression: Expression that contains arithmetic operators and operands • Precedence numbers: Indicate order of operations in expression • Performed from lower precedence numbers first to higher number • If two operations are at same level, they are performed left to right • Parentheses can be used to override default precedence Programming with Microsoft Visual Basic 2008, Fourth Edition

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