GUI使用JFrame和JPanel绘制自定义形状

Question

Pretty much I create a Shape class, with Rectangle , Circle , Triangle extending Shape , and a Square class extending Circle . I have the code working with this main class, but I'm having a tough time converting it into GUI because I'm not sure how to do number 3 to make this come together and how to make a g.drawOval(with given x,y & radius) and draw triangle(given x,y, base and height) .

1. Project6 class will have to extend the JFrame class
2. Project6 constructor will have to set up the GUI window.
3. A new abstract method: public void display(Graphics g); should be added to the base and derived classes.
4. A custom JPanel must be set up with a paintComponent method
5. The new display(Graphics g) method will have to draw the shapes on the GUI window and be called from a loop in the paintComponent method.

---

import javax.swing.*;
import java.awt.*;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Project6 extends JFrame {   

private Shape [] thearray = new Shape[100]; 

public static void main (String [] args) {

Project6 tpo = new Project6();
tpo.run();
}

public void run () {
int count = 0;

thearray[count++] = new Circle(20, 20, 40);
thearray[count++] = new Triangle(70, 70, 20, 30);
thearray[count++] = new Rectangle(150, 150, 40, 40);
thearray[count++] = new Square(100, 100, 50, 75);

for (int i = 0; i < count; i ++ ) {    
   thearray[i].display();              
 }  

int offset = 0;
double totalarea = 0.0;
while (thearray[offset] != null) {          
   totalarea = totalarea + thearray[offset].area();   
   offset++;
} 
System.out.println("The total area for " + offset + " Shape objects is " + totalarea);
}

public Project6() {
JFrame frame = new JFrame();
frame.setSize(800, 700);                           
frame.setTitle("Shapes: Circle, Triangle, Rectangle, Square");
frame.setLocationRelativeTo(null);                 //Center Frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}  

public static class MyPanel extends JPanel {

  public static JPanel showJPanel(Graphics g) {
   panel = new MyPanel();
   return panel;
   }

  @Override
  public void paintComponent(Graphics g) {
  super.paintComponent(g);
  for(int i = 0; i < thearray.length && thearray[i] != null; i++) {
  thearray[i].display();

Do I add something like this at the end of each of my classes? IE Circle , Square , Triangle , Rectangle class?

 @Override
 public void draw(Graphics g) {
  g.drawRect(getXPos(), getYPos(), width, height);
  }

---

I can't change the way the array is set up, but isn't this supposed to be the class that extends JFrame?

 public Project6() {
 JFrame frame = new JFrame();
 frame.setSize(800, 700);                           
 frame.setTitle("Shapes: Circle, Triangle, Rectangle, Square");
 frame.setLocationRelativeTo(null);                 //Center Frame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.setVisible(true);
 }  

I'm new to GUI so this is a little hard to do, but would this work for drawing the shapes? But I get an error saying nonstatic method get() cant be referenced from static context

class NewPanel extends JPanel {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(Triangle.getXPos(), 0, 0, Triangle.getYPos());
g.drawLine(Triangle.getXPos(), 0, Triangle.getXPos, Triangle.getYPos());
g.drawLine(Triangle.getXPos(), Triangle.getYPos, 0, Triangle.getYPos());
g.drawRect(Rectangle.getXPos(), Rectangle.getYPos(), Rectangle.getWidth(), Rectangle.getHeight());
g.drawRect(Square.getXPos(), Square.getYPos(), Square.getWidth(), Square.getHeight());
g.drawOval(Circle.getXPos(), Circle.getYPos(), Circle.getRadius(), 10);

for(int i = 0; i < thearray.length && thearray[i] != null; i++) {
thearray[i].display();
}
} 

Answer 1

1. Your class extends a JFrame that is never displayed
2. You should draw your shapes in the paintComponent method of a JPanel, one that is added to your JFrame.
3. I would use an ArrayList<Shape> , not an array, since this way I'd be able to add as many or as few Shapes to my collection and not have to worry about null items.
4. I'd then iterate through the collection in the paintComponent method override and draw each Shape using a Graphics2D object.
5. Regarding your last question, "Do I add something like this at the end of each of my classes? ie(Circle, square, triangle, rectangle class?..." no, there's no need for a "draw" method since you'll be using the paintComponent method to do your drawing.