Lecture 11

Lecture Topic:

• Abstract Window Toolkit
• Graphic Class
• Transformation Class
• 
  
•  
• 
  
• Quiz

Abstract Window Toolkit

-- Abstract Window Toolkit(AWT) implements most common window functionality.  
It contains a set of window object classes that creates windows, menus, and 
dialogs.
 

Following code using synchronized method to paint the clock.
 
	Public Static Digital Threads clock_thread;
	Public Static void main( String[]args) {
		clock_thread = new Digital Threads();
		void start_clock() {
		clock_thread g = getgraphic();	// get grapic
		clock_thread f = main_frame;	// get frame
		clock_thread.start();		// start clock draw
		}	
	}
	
	Synchronized Public void Paint(graphics g) {
		start_clock();
		draw_grid(g);
		compute_range();
		int numShapes = drawnShapes.Size();
		Shape S;
		for (int i = 0; i < numShapes; i++) {
		  S = (Shape)drawnShapes.elementAt(i);
		  S.draw(g);
		}
	}
 

Graphic Class

-- The Graphics class is part of the java.awt package.  It can be used
to draw lines, shapes, images and characters to the screen.
 

Usage:
 
	import java.awt.Graphics;
 
	public class MyClass extends java.applet.Applet {
	...
	}
 

Example 1: function draws grid.
 
	void drawgrid(graphics g)	{
		Ractangle r;
		r = bounds();
		int grid_spacing = 20;
		for (int x=0; x < r.width; x=x+grid_spacing) {
			g.drawLine(x, 0, x, r.height);
			}
		for (int y=0; y < r.winth; y=y+grid_spacing) {
			g.drawLine(0, y, r.width, y);
			}
	}
 
 
Example 2:  function draws a special line.
 
	void line(Graphics g, point P1, point P2)  {
		g.drawLine(Sx(P1.x), Sy(P1.y), Sx(P2.x), Sy(P2.y));
	}
 
	int Sx(double x) {
	  return round(display.scale.x*x + display.translate.x);
	}
 
	int SY(double y) {
	  return round(display.scale.y*y - display.translate.y);
	}
 
Example 3:  functions draws string and fills circle.
 
	void string(Graphics g, string str, Point p)  {
		g.drawString(str, Sx(p.x), Sy(p.y));
		{
 
	void fill_circle(Graphics g, Point p, int radius)  {
		g.fillOval(Sx(p.x), Sy(p.y), radius, radius);
		}
 
 

Transformation class

-- It performs translation, rotation, rescale and shear.
Example :
	
	Xform display = center;
	Xform center = new Xform(120, -120, 1, -1);
 
	class Xform {
		public Point translate;
		public Point scale;
		Xform(double tx, double ty, double sx, double sy)  { 
			translate = new Point(tx, ty);
			translate = new Point(sx, sy);
			}
 
		// translate the position of the matrix
		void move(double dx, double dy) {
			 translate.x = translate.x + dx; 
			 translate.y = translate.y + dy; 
			}
		// translate the scale of the matrix
		void rscale(double sx, double sy) {
			 translate.x = translate.x * sx; 
			 translate.y = translate.y * sy; 
			}
 
		}

1. AWT is a class library made up of various windows component classes.
  a. True.
  b. False.
 
2. Graphics Class is in the Abstract Window Toolkit.
  a. True.
  b. False.