Java Programming (12.2)----polymorphism, listener Beginner application: Draw a graphic in a window, you can select a circular square line

1. Add 3 buttons to the 800 *800 window to select the current brush to draw what kind of shape has a circle square straight line three kinds

JFrame Listener uses internal class anonymous internal class interface polymorphism

1. Abstract class for all graphs first

Package Com.lovo.homework;import Java.awt.color;import java.awt.graphics;/** * Abstract class: Graphics * @author Abe * Properties: Start coordinates end coordinates color */PU  Blic abstract class Figure {protected int startX, starty;protected int endx, endy;protected Color color;/** * constructor */public Figure () {This.color = This.radomcolor ();} /** * Method: Random color */public color Radomcolor () {int r = (int) (Math.random () * n); int g = (int) (Math.random () * n); int b = (int) (Math.random () * 256); Color color = new Color (r, G, b); return color;} /** * Method: Get and set//Do not know to use the first addition to say * @return */public int getstartx () {return startX;} public void Setstartx (int startX) {this.startx = StartX;} public int Getstarty () {return starty;} public void Setstarty (int starty) {this.starty = Starty;} public int getendx () {return endx;} public void setendx (int endx) {this.endx = EndX;} public int Getendy () {return endY;} public void Setendy (int endY) {this.endy = EndY;} Public Color GetColor () {return Color;} /** * Abstract Method Drawing * @param g */public abstract void Draw (Graphics g);} 

2. Class: Round

Package Com.lovo.homework;import java.awt.graphics;/** * Class: Circle * Parent class: Graphics * @author Abe  */public class Circle extends Figu re{@Overridepublic void Draw (Graphics g) {G.setcolor (This.radomcolor ());//Rewrite drawing method  inherits the teacher's xy judgment int x = StartX < EndX ? Startx:endx;int y = starty < EndY? Starty:endy;g.drawoval (x, Y, Math.Abs (ENDX-STARTX), Math.Abs (Endy-starty));}}

3. Class: Square

Package com.lovo.homework;/** * Class: Square * @author Abe * Parent class: Figrue Graphics  */import java.awt.graphics;public class Ractangle Extends Figure {@Overridepublic void Draw (Graphics g) {//Rewrite the drawing method, the result of plotting with a method of swapping size feels a lot more trouble G.setcolor (This.radomcolor ()) ;//Optimized the coordinates of the next teacher to determine the method int x = Math.min (StartX, endx); int y = Math.min (starty, EndY); G.drawrect (x, Y, Math.Abs (endx-startx), Ma Th.abs (Endy-starty));}}

4. Class: Straight Line

Package Com.lovo.homework;import java.awt.graphics;/** * Class: Straight line * Parent class: Figure * @author Abe */public class lines extends figure {@Overridepublic void Draw (Graphics g) {G.setcolor (This.radomcolor ()); G.drawline (StartX, Starty,endx,endy);}}

5. Draw window, add event listener, add Mouse listener (adapter)

adapters, for inheritance, only with the functionality required for rewriting, other automatic soy sauce

Package Com.lovo.homework;import Java.awt.button;import Java.awt.graphics;import java.awt.event.actionevent;import Java.awt.event.actionlistener;import Java.awt.event.mouseadapter;import java.awt.event.mouseevent;/** * class: Drawing window * Parent class: JFrame * @author Abe */import javax.swing.JFrame; @SuppressWarnings ("Serial")//Don't know what the goods mean MyFrame automatically fix public class MyFrame extends JFrame {private Button B1 = New button ("Circle");p rivate button b2 = New button ("Rectangle");p rivate button B3 = new  Button ("line segment");p rivate Figure fig = null;private Boolean Boo = true;/** * Inner class: Event listener * @author Abe */public class Mylistenner Implements ActionListener {//interface event listener @overridepublic void actionperformed (ActionEvent e) {Object obj = E.getsource (); if ( obj = = B1) {fig = new Circle (),} else if (obj = = b2) {fig = new Ractangle ();} else if (obj = = B3) {fig = new line ();}}} /** * Inner class: Mouse adapter * @param e */public class Mymouseadapter extends Mouseadapter {//inherit mouse adapter @overridepublic void mousepressed (MouseEvent e) {//Override Click event if (Fig! = null) {Fig. Setstartx (E.getx ()); Fig.setstarty (E.gety ()); Fig.setendx (E.getx ()); Fig.setendy (E.gety ());}} @Overridepublic void mousedragged (MouseEvent e) {//Override drag event if (fig! = null) {Fig.setendx (E.getx ()); Fig.setendy (E.gety ()) ; repaint ();}}} /** * Constructor */public MyFrame () {This.settitle ("selection tool painting"); This.setsize (+) this.setdefaultcloseoperation (exit_on_ CLOSE); this.setresizable (false); This.setlocationrelativeto (null); This.setlayout (null); B1.setbounds (220, 10, 75, (b2.setbounds); B3.setbounds (480, ten, ()), This.add (B1); This.add (B2); This.add (b3); Mymouseadapter adapter = new Mymouseadapter (); This.addmouselistener (adapter); This.addmousemotionlistener (adapter); Mylistenner L = new Mylistenner (); B1.addactionlistener (L); B2.addactionlistener (L); B3.addactionlistener (l);} /** * Rewrite drawing method */@Overridepublic void Paint (Graphics g) {if (boo! = True) {g.clearrect (0, 0, +); boo = true;} Super.paint (g);//enable the window without a shadow to see only the last drawn graphic if (fig! = null) {Fig.draw (g);}} public static void Main (string[] args){New MyFrame (). setvisible (True);}} 

The drawing effect looks unreal, but when you refresh the window, only the last graphic is displayed.

I wanted to save it with a number of groups, but once the array is instantiated, it doesn't add up ... Or would you like to save 3 graphs with 3 arrays?  Feel Good trouble ... There should be a better way ...

Java Programming (12.2)----polymorphism, listener Beginner application: Draw a graphic in a window, you can select a circular square line