chapter 4 windows forms gui/edp yingcai xiao. .net gui forms and controls
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Chapter 4Windows Forms
GUI/EDP
Yingcai Xiao
.NET GUIForms and Controls
Concepts: GUI Windows Forms—for writing GUI based applications
(Windows Applications).
GUI: Graphical User Interface, to make programs easy to use, WYSIWYG (What you see is what you get).
Designing GUI-based Applications: Look & FeelLook => Appearance (Layout Design)Feel => Response (Event Handling) User => Button Click => Event => Event Handler (a method).GUI-based application => Event-driven programming
• Two main tasks of GUI-based EDP:Design interface appearance (look)Implement even handlers (feel).
Concepts: GUI Design Principles
Users first: let users control the program not the other way around.
Elegant: simple but powerful. E.g.: iPot, iPhone, Google Intuitive: don’t need too much training to use it. Compare
operating interfaces of cars and airplanes. Clarity: use icons and keywords that are standardized or clearly
defined. (AWK?). Give users hints when they hesitating. Hierarchical: only put the most frequently used and most
important controls at the top level. Speedy: users do not have patience to wait for too long. Forgiving: allow users to make mistakes. Undo and redo. Alignment: use tables. Internationalization: use symbols. More: http://www.iie.org.mx/Monitor/v01n03/ar_ihc2.htm
http://www.asktog.com/basics/firstPrinciples.html
.NET GUI Classes (Event Generators)
GUI Items are defined in System.Windows.Forms.System.Windows.Forms.Form class: all forms derive from it.
Properties (can be treated as “public” data members): ClientRectangle (drawing area not including the borders)
ClientSizeBorderStyleText (Title Bar)
Methods: OnPaint (event handler for the PAINT event)
System.Windows.Forms Control Classes
Controls (Windows GUI Items)
Class Descriptionss
Button Push buttons
CheckBox Check boxes
CheckedListBox List boxes whose items include check boxes
ComboBox Combo boxes
DataGrid Controls that display tabular data
DataGridTextBox Edit controls hosted by DataGrid controls
DateTimePicker Controls for selecting dates and times
Controls (Windows GUI Items) Cont.
System.Windows.Forms Control Classes
GroupBox Group boxes
HScrollBar Horizontal scroll bars
Label Label controls that display static text
LinkLabel Label controls that display
hyperlinks
ListBox List boxes
ListView List views (display flat lists of items in a variety of
styles)
MonthCalendar Month-calendar controls
Controls (Windows GUI Items) Cont.
System.Windows.Forms Control Classes
NumericUpDown Spinner buttons (up-down
controls)
PictureBox Controls that display
images PrintPreviewControl Controls that display print
previews
ProgressBar Progress bars
PropertyGrid Controls that list the properties of other objects
RadioButton Radio buttons
RichTextBox Rich-edit controls
Controls (Windows GUI Items) Cont.
System.Windows.Forms Control Classes
StatusBar Status bars
TabControl Tab controls
TextBox Edit controls
ToolBar Toolbars
ToolTip Tooltips
TrackBar Track bars (slider controls)
TreeView Tree views (display hierarchical lists of items)
VScrollBar Vertical scroll bars
Programming a GUI APP using VS
1. Start Visual Studio2. New project3. Windows Forms Application4. Toolbox->Button: drag it to Form15. Double click on button1 in Form16. Add to button1_Click
this->button1->Text = "Hello!";
Build and run
Programming a GUI APP using Notepad
1. Use Notepad to write the program2. Create your form (GUI) by sub-classing System.Windows.Forms.Form.3. Add controls (GUI items) to the form. 4. Code your program logic.5. Compile the program using csc.
Example:T:\Xiao\Windows Programming\Examples\C4\DialogDemo\DialogDemo.cs
Programming a Control
1. Instantiate the corresponding control class.2. Initialize the control by setting its property values.3. Add the control to the form by calling
the “Add” method of the form’s Controls collection.4. Map event handlers to the events.5. Implement the event handlers.
Adding a Button to a Form
//Create and initialize the buttonButton MyButton = new Button ();MyButton.Location = new Point (16, 16);MyButton.Size = new Size (96, 24);MyButton.Text = "Click Me";
// add the button to the form’s Controls collection.Controls.Add (MyButton);
// Add event handlers to eventsMyButton.Click += new EventHandler (OnButtonClicked);
// Write the event handlers void OnButtonClicked (Object sender, EventArgs e){… }
T:\Xiao\Windows Programming\Examples\C4\DialogDemo\DialogDemo.cs
Common Dialog Classes Defined in System.Windows.Forms
Dialog Boxes
Class Dialog Type ColorDialog Color dialog boxes for choosing
colors FontDialog Font dialog boxes for choosing fonts OpenFileDialog Open File dialog boxes for choosing
files
PageSetupDialog Page Setup dialog boxes for entering page setup parameters
PrintDialog Print dialog boxes for entering print
parameters SaveFileDialog Save File dialog boxes for entering
file names
class MyDialog : Form{ Label WidthLabel; TextBox WidthBox; Button OKButton;
public int UserWidth { get { return Convert.ToInt32 (WidthBox.Text); } set { WidthBox.Text = value.ToString (); } }
public MyDialog () { // Initialize the dialog's visual properties ClientSize = new Size (296, 196); StartPosition = FormStartPosition.CenterParent; FormBorderStyle = FormBorderStyle.FixedDialog; Text = "Edit Ellipse"; ShowInTaskbar = false;
DialogDemo.cs
// Create the dialog's controls WidthLabel = new Label (); WidthLabel.Location = new Point (16, 16); WidthLabel.Size = new Size (48, 24); WidthLabel.Text = "Width";
WidthBox = new TextBox (); WidthBox.Location = new Point (64, 12); WidthBox.Size = new Size (96, 24); WidthBox.TabIndex = 1;
DialogDemo.cs
OKButton = new Button (); OKButton.Location = new Point (184, 12); OKButton.Size = new Size (96, 24); OKButton.TabIndex = 3; OKButton.Text = "OK"; OKButton.DialogResult = DialogResult.OK;
AcceptButton = OKButton;
// Add the controls to the dialog Controls.Add (WidthLabel); Controls.Add (WidthBox); Controls.Add (OKButton);} }
DialogDemo.cs
DialogDemo.cs
// In the parent form who starts the dialog:MyDialog dlg = new MyDialog ();if (dlg.ShowDialog (this) == DialogResult.OK) {
MyWidth = dlg.UserWidth; // get the input from the formInvalidate (); // update the display of the parent form
}
EDP
Concepts: EDP
Event-Driven Programming (EDP): Application waits (idles)
after initialization until the user generates an event trough an input device (keyboard, mouse, …). The OS dispatches the event to the application who owns the active window. The corresponding event handler(s) of the application is invoked to process the event.
Events
A menu in C++:
char c;bool done = false;while(!done) {
cout << “Please make your selection, q to end:”cin >> c;switch(c) {case “+”:
add( );break;
case “-”:sub( ); break;
case “q”:done = true; break;
}}
Event Loop
Event Mapping&
Even Dispatching
Event
Event Handler
(1) Event Generators: keyboard, GUI items (buttons, menus, …), NUI
devices. (2) Events / Messages:
MouseClick, KeyDown, …(3) Event Loop:
an infinite loop constantly waits for events. (4) Event Mapping / Event Registration:
inform event dispatcher which event an event hander is for.
(5) Event Dispatcher: dispatch events to the corresponding event handlers.
(6) Event Handlers:methods for processing events.OnMouseClick(), …
Key Components of EDP
(1) Event Generators- commonly used GUI items are predefined. - used by programmers / GUI designers.
(2) Events / Messages - commonly used ones predefined.
(3) Event Loop: - taken care of by .NET. (4) Event Mapping / Registration:
- implemented by .NET. - to be used by the programmers
with appropriate matching: event – delegate – even handler
(5) Event Dispatching: - taken care of by .NET. (6) Event Handlers
- to be implemented by programmers.
Key Components of EDP in .NET
(1) GUI Items (Event Generators)System.Windows.Forms.FormButton, Dialog, ….
(2) Events: predefined Windows Messages:e.g. WM_KEYDOWN
(3) Event Loop:Built in System.Windows.Forms.Application Class: static Run( ) method starts an application’s event loop.
.NET EDP Classes
(4) Event Mapping / Registration:System defined ones have their names fixed: e.g. OnPaint().Other handlers need to be registered to the events with their corresponding delegates by the programmer.e.g. :
MyButton.Click += new EventHandler (OnButtonClicked); The Resource Editor will do this automatically
when the programmer double-clicks on a button. (5) Event Dispatching:
Built in: HW->OS->Active Application->Event Object->Delegate:Invoke->Handlers. .
.NET EDP Classes
(6) Event Handlers:Programmers’ work.void HandlerName (Object sender, EventArgs e) //sender can be omitted. HandlerName = “On” “EventName”e.g. OnKeyDown(Object sender, EventArgs e);
.NET based GUI EDP:①Identify needed GUI items; code or visually design GUI.②Identify related event; register event handlers with the
events via their delegates.③Implement event handlers.
.NET EDP Classes
Mouse and Keyboard Events/Handlers
OnKeyDown A key is pressed KeyEventArgs
OnKeyPress A character is typed on the keyboard
KeyPressEventArgs
OnKeyUp A key is released KeyEventArgs
OnMouseDown A mouse button is pressed MouseEventArgs
OnMouseEnter The mouse cursor enters a form
EventArgs
OnMouseOver The mouse cursor pauses
over a form EventArgs
Mouse and Keyboard Events/Handlers
OnMouseLeave The mouse cursor leaves a form
EventArgs
OnMouseMove The mouse cursor moves over a form
MouseEventArgs
OnMouseUp A mouse button is
released MouseEventArgs
OnMouseWheel The mouse wheel is rolled
MouseEventArgs
WM_KEYDOWN protected override void OnKeyDown (KeyEventArgs e) { // from the form if (e.KeyCode == Keys.F1) // Function key F1 was pressed { … }}
WM_CHAR protected override void OnKeyPress (KeyPressEventArgs e){
if (e.KeyChar == 'C') { … } // Do something
}
Mouse and Keyboard Events/Handlers
Other Form-Level Events
OnActivated A form is activated
OnClosed A form is closed
OnClosing A form is about to close
OnDeactivate A form is deactivated
OnGotFocus A form receives the input focus
OnLoad A form is created
OnLocationChanged A form is moved
OnLostFocus A form loses the input focus
OnPaintBackground A form’s background needs repainting
OnSizeChanged A form is resized
// Create a MainMenu objectMainMenu menu = new MainMenu ();
// Add a File menu and populate it with itemsMenuItem item = menu.MenuItems.Add ("&File");item.MenuItems.Add ("&New", new EventHandler (OnFileNew));item.MenuItems.Add ("&Open...", new EventHandler (OnFileOpen));
// Add an Edit menu and populate it, tooitem = menu.MenuItems.Add ("&Edit");item.MenuItems.Add ("Cu&t", new EventHandler (OnEditCut));
Processing Menu Commandsvoid HandlerName (Object sender, EventArgs e)
Main Menus: top-level menu.
Context Menus: pop up context menus
ContextMenu menu = new ContextMenu ();menu.MenuItems.Add ("&Open", new EventHandler (OnOpen));menu.MenuItems.Add ("&Rename", new EventHandler (OnRename));menu.MenuItems.Add ("&Delete", new EventHandler (OnDelete));menu.Show (this, new Point (x, y));
Menu Item States: item.Checked = true;
Context Menus
Shortcut keys: key combinations to directly invoke a commande.g. Control O to open a fileitem.MenuItems.Add (new MenuItem ("&Open...",
new EventHandler (OnFileOpen), Shortcut.CtrlO)); http://www.computerhope.com/shortcut.htm
• Keyboard Accelerators: to help accessing a menu item without using the mouse. An accelerator key related to a menu item is preceded with an “&” and is displayed underlined.
e.g. Alt F to access the File menus, then O to open a fileitem.MenuItems.Add (new MenuItem ("&Open...",
new EventHandler (OnFileOpen), Shortcut.CtrlO)); Microsoft defines Keyboard Accelerators the same as Shortcuts.http://msdn.microsoft.com/en-us/library/ms645526(VS.85).aspx
Shortcuts and Accelerators
.NET Drawing Classes: in System.Drawing.
Graphics Device Interface (GDI) software to interface with the graphics hardware.
GDI+ Graphics Primitives (System.Drawing.Drawing2D): Bitmap, Font, HatchBrush, LinearGradientBrush, Pen, SolidBrush, TextureBrush, DrawArc, DrawCurve, DrawEllipse, DrawIcon, DrawImage, DrawLine, DrawPie, DrawPolygon, DrawString, FillEllipse, FillPie, FillPolygon, FillRectangle.
Drawing in .NET
GDI+ : stateless, a form passes parameters detailing output characteristics to every Graphics method it calls. For (stateless) Internet use.
Old Windows GDI: stateful, drawing parameters are stored as state variables in the GDI’s device context.
Example: DialogDemo.cs – OnPaint(PaintEventArgs e)
Dispose your GDI+ Objects to avoid running out of GDI+ resourses. e.g. brush.Dispose();
Drawing in .NET cont.
DirectX: Direct3D, DirectMusic, DirectSound. Xbox (based on DirectX): Video GameXNA (Xbox New Architecture, XNA is Not an Acronym):
Video Game development and management
WPF: Windows Presentation Foundation Introduced in .NET 3.0 Based on DirectX, not GDI 2D and 3D
GDI and Beyond
Summary
GUI-based windows application development:
GUI-based programming. forms and controls, look and feelEDPevents and handlersGDI
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