![List Boxes Great for displaying / maintaining list of data list of strings list of objects (list box calls ToString() to display) Customer[] customers; . . // create & fill array with objects... . // display customers in list box foreach (Customer c in customers) this.listBox1.Items.Add(c); // display name of selected customer (if any) Customer c; c = (Customer) this.listBox1.SelectedItem; if (c == null) return; else MessageBox.Show(c.Name);](https://image.slidesharecdn.com/06winforms-110307020055-phpapp02/85/06-win-forms-36-320.jpg)
06 win forms
- 1. 6. WinForms: GUI Programming in .NET
- 2. Objectives “ .NET supports two types of form-based apps, WinForms and WebForms . WinForms are the traditional, desktop GUI apps. The great news is that Visual Studio .NET enables quick, drag-and-drop construction of form-based applications…” Event-driven, code-behind programming Visual Studio .NET WinForms Controls
- 3. Part 1 Event-driven, code-behind programming…
- 4. Event-driven applications Idea is very simple: individual user actions are translated into “events” events are passed, 1 by 1, to application for processing this is how most GUIs are programmed… GUI App
- 5. GUI-based events Mouse move Mouse click Mouse double-click Key press Button click Menu selection Change in focus Window activation etc.
- 6. Code-behind Events are handled by methods that live behind visual interface known as "code-behind" our job is to program these methods…
- 7. Call-backs Events are a call from object back to us… How is connection made? setup by code auto-generated by Visual Studio
- 8. Part 2 Visual Studio .NET…
- 9. Visual Studio .NET (VS.NET) A single IDE for all forms of .NET development from class libraries to form-based apps to web services and using C#, VB, C++, J#, etc.
- 10. Basic operation Visual Studio operates in one of 3 modes: design run break When in doubt, check the title bar of VS… design run break
- 11. Example: a windowing application GUI apps are based on the notion of forms and controls … a form represents a window a form contains 0 or more controls a control interacts with the user Let's create a GUI app in a series of steps…
- 12. Step 1 Create a new project of type “Windows Application” a form will be created for you automatically…
- 13. Step 2 — GUI design Select desired controls from toolbox… hover mouse over toolbox to reveal drag-and-drop onto form position and resize control
- 14. GUI design cont’d… A simple calculator: Position and configure controls click to select set properties via Properties window
- 15. Step 3 — code design “Code behind” the form… Double-click the control you want to program reveals coding window
- 16. Step 4 — run mode Run!
- 17. Break mode? Easily triggered in this application via invalid input…
- 18. Working with Visual Studio In Visual Studio, you work in terms of source files, projects & solutions Source files contain code end in .cs, .vb, etc. Project files represent 1 assembly used by VS to keep track of source files all source files must be in the same language end in .csproj, .vbproj, etc. Solution (*.sln) files keep track of projects so you can work on multiple projects
- 19. Part 3 WinForms…
- 20. WinForms Another name for traditional, Windows-like GUI applications vs. WebForms, which are web-based Implemented using FCL hence portable to any .NET platform
- 21. Abstraction FCL acts as a layer of abstraction separates WinForm app from underlying platform System.Windows.Forms.Form CLR Windows OS instance of FCL class object
- 22. Form properties Form properties typically control visual appearance: AutoScroll BackgroundImage ControlBox FormBorderStyle (sizable?) Icon Location Size StartPosition Text (i.e. window's caption) WindowState (minimized, maximized, normal) Form1 form; form = new Form1(); form.WindowState = FormWindowState.Maximized; form.Show();
- 23. Form methods Actions you can perform on a form: Activate : give this form the focus Close : close & release associated resources Hide : hide, but retain resources to show form later Refresh : redraw Show : make form visible on the screen, & activate ShowDialog : show modally form.Hide(); . . . form.Show();
- 24. Form events Events you can respond to: bring up properties window double-click on event name Load : occurs just before form is shown for first time Closing : occurs as form is being closed (ability to cancel) Closed : occurs as form is definitely being closed Resize : occurs after user resizes form Click : occurs when user clicks on form's background KeyPress : occurs when form has focus & user presses key
- 25. Example Ask user before closing form: private void Form1_Closing (object sender, System.ComponentModel.CancelEventArgs e) { DialogResult r; r = MessageBox.Show("Do you really want to close?", "MyApp", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button1); if (r == DialogResult.No) e.Cancel = true; }
- 26. Part 4 Controls…
- 27. Controls User-interface objects on the form: labels buttons text boxes menus list & combo boxes option buttons check boxes etc.
- 28. Abstraction Like forms, controls are based on classes in the FCL: System.Windows.Forms.Label System.Windows.Forms.TextBox System.Windows.Forms.Button etc. Controls are instances of these classes object object object object object object
- 29. Who creates all these objects? Who is responsible for creating control instances? code is auto-generated by Visual Studio when form object is created, controls are then created…
- 30. Naming conventions Set control's name via Name property A common naming scheme is based on prefixes: cmdOK refers to a command button control lstNames refers to a list box control txtFirstName refers to a text box control
- 31. Labels For static display of text used to label other things on the form used to display read-only results Interesting properties: Text : what user sees Font : how he/she sees it
- 32. Command buttons For the user to click & perform a task Interesting properties: Text : what user sees Font : how he/she sees it Enabled : can it be clicked Interesting events: Click : occurs when button is "pressed" private void cmdAdd_Click (...) { int i, j, k; i = System.Convert.ToInt32( this.txtNum1.Text ); j = System.Convert.ToInt32( this.txtNum2.Text ); k = i + j; MessageBox.Show( "Sum = " + k.ToString() ); }
- 33. Text boxes Most commonly used control! for displaying text for data entry Lots of interesting features…
- 34. Text box properties Basic properties: Text : denotes the entire contents of text box (a string) Modified : has text been modified by user? (True / False) ReadOnly : set if you want user to view text, but not modify Do you want multi-line text boxes? MultiLine : True allows multiple lines of text Lines : array of strings, one for each line in text box ScrollBars : none, horizontal, vertical, or both
- 35. Text box events Interesting events: Enter , Leave : occurs on change in focus KeyPress : occurs on ascii keypress KeyDown , KeyUp : occurs on any key combination TextChanged : occurs whenever text is modified Validating and Validated Validating gives you a chance to cancel on invalid input
- 36. List Boxes Great for displaying / maintaining list of data list of strings list of objects (list box calls ToString() to display) Customer[] customers; . . // create & fill array with objects... . // display customers in list box foreach (Customer c in customers) this.listBox1.Items.Add(c); // display name of selected customer (if any) Customer c; c = (Customer) this.listBox1.SelectedItem; if (c == null) return; else MessageBox.Show(c.Name);
- 37. Just the tip of the iceberg… Menus, dialogs, toolbars, etc. Thousands of additional controls .NET and ActiveX right-click on Toolbox "Customize Toolbox"
- 38. Summary Event-driven programming is very intuitive for GUI apps Forms are the first step in GUI design each form represents a window on the screen form designer enables drag-and-drop GUI construction Users interact primarily with form's controls labels, text boxes, buttons, etc. implies that GUI programming is control programming
- 39. References Books: R. Grimes, "Developing Applications with Visual Studio .NET" Best books on building GUIs are VB-based: J. Savage, "The VB.NET Coach" (introductory) F. Balena, "Programming Microsoft VB .NET (Core Reference)" (broad coverage, intermediate level)
- 40. Lab? Work on lab #3, "WinForms"…