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CSC 298

CSC 298. Windows Forms. Programming Windows Forms. Use the FCL classes in the namespace System.Windows.Forms, e.g. Form: most Windows Forms applications derive from Form Application: the Run method provides the message loop to handle the interaction of the user with the Form

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CSC 298

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  1. CSC 298 Windows Forms

  2. Programming Windows Forms • Use the FCL classes in the namespace System.Windows.Forms, e.g. • Form: most Windows Forms applications derive from Form • Application: the Run method provides the message loop to handle the interaction of the user with the Form • Use also the classes in System.Drawing for graphics capabilities (Graphics Device Interface+ GDI+), e.g. the Graphics class.

  3. Inheritance hierarchy of Form

  4. Using Forms • Know about common structs • Color (create your color with FromArgb) • Rectangle: upper left point (x,y), width, height • Size: width and height • Point: (x,y) • Know about the common form properties • ForeColor, BackColor, Font, ClientRectangle, • Practice: see class website

  5. Forms and events • Input model for forms is event driven • any action on the form by the user (mouse click, key pressed, etc…) is associated with a different method in a class • the user's action triggers a call to the method • To manage the user's actions, override these methods in the class that inherits Form • Common methods • OnMouseDown, OnMouseUp, OnMouseMove, OnPaint, etc…

  6. Event Methods • To override, write e.g. for OnPaint protected override void OnPaint(PaintEventArgs pea) { /* your code */ } • All event methods take an argument that describe the event, for instance • MouseEventArgs for mouse events • KeyEventArgs, KeyPressEventArgs for keyboard event • EventArgs for events that don't carry a particular description (resize event, change of the backcolor, etc…)

  7. Alternative: create an event handler • Create an event handler and attach it to the relevant event, e.g. public class MyForm: Form{ { public MyForm(){ PaintEventHandler myHandler = new PaintEventHandler(MyOnPaint);this.Paint += myHandler; // rest of the constructor } private void MyOnPaint(Object source, PaintEventArgs pea) {/* code */} }

  8. Delegates • Event handlers must match a method prototype called the delegate, defined as for instance public delegate void PaintEventHandler(Object source, PaintEventArgs pea); • Common event handlers • KeyEventHandler, MouseEventHandler, EventHandler • Common events on a form (look for ) • mouse: Click, MouseMove, MouseUp, MouseDown, etc… • keyboard: KeyDown, KeyUp, KeyPress • others: Resize, Closing, etc…

  9. Controls on a form • A form is a container. Thus it can have controls, e.g. buttons, radio buttons, check boxes… • Can't override the protected event methods for these controls since their classes are not inherited • Must use the event handler approach public class MyForm: Form{ private Button cmdOK = new Button(); public MyForm(){ cmdOK.Click += new EventHandler(CmdOnClick); } private void CmdOnClick(Object source, EventArgs ea){ /* code for click on OK button */ }

  10. Defining your own events • Rarely needed for common applications • Create your own delegate to define the prototype of the event handler public delegate void MyEventHandler(Object source, MyEventArgs mea); • Create a variable of the type defined by the delegate: the event public event MyEventHandler MyEvent; • The user of the class adds (+=) or removes (-=) event handlers to the event • See example (Phone.cs)

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