Todays topics Java Applications Graphics Upcoming Review for

Today’s topics Java Applications Graphics Upcoming Review for Midterm Exam Reading Great Ideas, Chapters 5 Comp. Sci 001 15. 1

Graphics v Java comes with drawing package q q v Use several new classes q q v Fairly limited Not hard to use Canvas Class Graphics Class Basics ideas q q Pixels Coordinates Comp. Sci 001 15. 2

Coordinate System v Origin at top left! 0, 0 X . (x, y) Y v Coordinates specified by giving x and y values q q x is to the right y is downward Comp. Sci 001 15. 3

Setting up Graphics v Declare Graphics and Canvas Graphics g; Canvas c; v Create Objects in init() c = new Canvas(); c. set. Size(200, 200); add(c); g = c. get. Graphics(); v Can now create graphical figures g. draw. Line(50, 150, 100); draws line from (50, 50) to (150, 100) : a diagonal line Comp. Sci 001 15. 4

Specifying Location and Size v v A (straight) line is specified by its endpoints A rectangle is specified by its top left corner and its width and height g. draw. Rect(50, 100, 50); v An oval is specified by its bounding box q q This is a rectangle into which an oval fits tightly The bounding box is specified like a rectangle g. draw. Oval(50, 100, 50); (50, 50) 50 Comp. Sci 001 100 15. 5

Graphics Demo public class GDemo extends java. applet. Applet implements Action. Listener { Graphics g; Canvas c; Button b 1, b 2, b 3, b 4; public void init() { c = new Canvas(); //new c. set. Size(200, 200); //new add(c); //new (sort of) g = c. get. Graphics(); //new b 1 = new Button("Start"); b 2 = new Button("Line"); b 3 = new Button("Oval"); b 4 = new Button("Rectangle"); Comp. Sci 001 15. 6

Graphics Demo. 2 b 1. add. Action. Listener(this); b 2. add. Action. Listener(this); b 3. add. Action. Listener(this); b 4. add. Action. Listener(this); add(b 1); add(b 2); add(b 3); add(b 4); } public void action. Performed(Action. Event event) { Object cause = event. get. Source(); if (cause == b 1) { g. set. Color(Color. white); // Color the whole canvas white g. fill. Rect(0, 0, 200); } Comp. Sci 001 15. 7

Graphics Demo. 3 if (cause == b 2) { g. set. Color(Color. blue); g. draw. Line(50, 150, 100); // Demonstrate draw. Line } if (cause == b 3) { g. set. Color(Color. green); g. draw. Oval(50, 100, 50); // Demonstrate draw. Oval } if (cause == b 4) { g. set. Color(Color. red); g. draw. Rect(50, 100, 50); // Demonstrate draw. Rect } } } Comp. Sci 001 15. 8

The Graphics Methods v v Used some additional methods Summary (method headers or signatures): Basic: void draw. Line(int x 1, int y 1, int x 2, int y 2) void draw. Rect(int x, int y, int width, int height) void draw. Oval(int x, int y, int width, int height) q Set color (before use): void set. Color(Color c) o Color. white, Color. red, Color. blue, Color. green q Versions filled with color: void fill. Rect(int x, int y, int width, int height) void fill. Oval(int x, int y, int width, int height) q Comp. Sci 001 15. 9

Flexibility v v Everything was fixed in first example Could (Should!) use variables q q q v v Allow Coordinates to be read in Allow (pre-programmed) shift for each button press Shown in next program Could do much more… Buttons and input could also control: q q q Color Dimensions (Height and Width) Filled or Not Comp. Sci 001 15. 10

Graphics with offsets public class GDemo 2 extends java. applet. Applet implements Action. Listener { Graphics g; Canvas c; Int. Field i. X, i. Y; Button b 1, b 2, b 3, b 4, b 5; int x, y; public void init() { c = new Canvas(); c. set. Size(200, 200); add(c); g = c. get. Graphics(); b 1 = new Button("Start"); b 2 = new Button("Oval"); b 3 = new Button("Rectangle"); b 4 = new Button("Set. Corner"); b 5 = new Button("Shift"); i. X = new Int. Field(20); i. Y = new Int. Field(20); Comp. Sci 001 15. 11

Graphics with offsets. 2 b 1. add. Action. Listener(this); b 2. add. Action. Listener(this); b 3. add. Action. Listener(this); b 5. add. Action. Listener(this); add(i. X); add(i. Y); add(b 1); add(b 2); add(b 3); add(b 4); add(b 5); } public void action. Performed(Action. Event event) { Object cause = event. get. Source(); if (cause == b 1) { g. set. Color(Color. white); // Color the whole canvas white g. fill. Rect(0, 0, 200); } Comp. Sci 001 15. 12

Graphics with offsets. 3 if (cause == b 2) { g. set. Color(Color. green); g. draw. Oval(x, y, 100, 50); // Demonstrate draw. Oval } if (cause == b 3) { g. set. Color(Color. red); g. draw. Rect(x, y, 100, 50); // Demonstrate draw. Rect } if (cause == b 4) { x = i. X. get. Int(); y = i. Y. get. Int(); } if (cause == b 5) { x = x + 5; y = y + 5; } } } Comp. Sci 001 15. 13

Array Defined Graphical Figure public class GDemo 3 extends java. applet. Applet implements Action. Listener { Graphics g; Canvas c; Button b 1, b 2; int x[] = {45, 95, 130, 95, 45, 10}; int y[] = {10, 45, 95, 130, 95, 45}; int n; public void init() { c = new Canvas(); c. set. Size(200, 200); add(c); g = c. get. Graphics(); b 1 = new Button("Start"); b 2 = new Button("String. Fig"); Comp. Sci 001 15. 14

Array Defined Graphical Figure. 2 b 1. add. Action. Listener(this); b 2. add. Action. Listener(this); add(b 1); add(b 2); n = 8; } public void action. Performed(Action. Event event) { Object cause = event. get. Source(); if (cause == b 1) { g. set. Color(Color. white); // Color the whole canvas white g. fill. Rect(0, 0, 200); } Comp. Sci 001 15. 15

Array Defined Graphical Figure. 3 if (cause == b 2) { int k, j; k = 0; g. set. Color(Color. blue); while (k < n) { j = 0; while (j < n) { g. draw. Line(x[k], y[k], x[j], y[j]); j = j + 1; } k = k + 1; } } Comp. Sci 001 15. 16