有没有办法从同一类中的另一个方法在JPanel上绘制形状？

Question

I am working to develop a GUI in which I paint some 2D shapes repeatedly on different locations. Currently I am having a method createGUI() that creates the basic layout and the panels and then I call the constructor for the content_panel to create 2D shapes in the content_panel.

But, I want to use another method to create the shapes in the main JPanel. Is there a way in Java, so that I can have two method calls in main. First method createGUI() creates the GUI including JFrames and JPanel. While the second method createShapes() creates shapes in the one specific JPanel - content_panel. I would like to call this createShapes() method repeatedly and pass different arguments to see shapes at different locations.

Please let me know if you need some more info or the question is unclear. Thanks

Code:

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class Board{

public static void main(String[] args)
{
    createGUI();
    drawShapes();
}

//This method creates the basic GUI 
private static void createGUI()
{
    //Creating the JFrame main window
    JFrame mainFrame = new JFrame();
    mainFrame.setSize(800, 500);
    mainFrame.setTitle("Particle Filter");
    mainFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    mainFrame.setLocation(100, 100);
    mainFrame.getContentPane().setLayout(new BoxLayout(mainFrame.getContentPane(), BoxLayout.X_AXIS));

    //creates two panels content and sidebar. Sidebar has null layout       
    JPanel content = new JPanel();
    content.setPreferredSize(new Dimension(700,500));
    content.setBackground(Color.LIGHT_GRAY);
    mainFrame.getContentPane().add(content);
    JPanel sidebar = new JPanel();
    sidebar.setBackground(Color.LIGHT_GRAY);
    sidebar.setPreferredSize(new Dimension(100,500));
    mainFrame.getContentPane().add(sidebar);
    sidebar.setLayout(null);

    //creates three buttons in sidebar
    JButton start_button = new JButton("START");
    start_button.setBounds(10, 75, 77, 23);
    sidebar.add(start_button);
    JButton stop_button = new JButton("STOP");
    stop_button.setBounds(10, 109, 77, 23);
    sidebar.add(stop_button);
    JButton reset_button = new JButton("RESET");
    reset_button.setBounds(10, 381, 77, 23);
    sidebar.add(reset_button);

    //calls the content_Walls class and sends the number of ovals to be generated
    int n=1000; // n denotes the number of ovals
    content.add( new Content_Walls(n));
    mainFrame.setVisible(true);

}

private static void drawShapes()
{

}

}
    class Content_Walls extends JPanel
    {


    ArrayList<Integer> list;

    Content_Walls(int n)
    {
        setPreferredSize(new Dimension(680,450));
        setBackground(Color.WHITE);
        list = new ArrayList<Integer>(Collections.nCopies(n, 0));
    }       

    public void paintComponent(Graphics g)
    {
        int x=0,y=0;
        super.paintComponent(g);

        createObstacles(g,150,225,100,40);
        createObstacles(g,500,300,40,100);

        for(int i=0;i<list.size();i++)
        {
            x=randomInteger(11,670); // bounds of x between which the particles should be generated 
            y=randomInteger(11,440); // bounds of y between which the particles should be generated 

            int radius = 4;

            x=x-(radius/2);
            y=y-(radius/2);
            g.fillOval(x, y, radius, radius);
        }

    private void createObstacles(Graphics g, int x, int y, int width, int height)
    {
        g.setColor(Color.BLACK);
        g.fillRect(x, y, width, height);
    }


    private static int randomInteger(int min, int max)
    {
        Random rand = new Random();
        int randomNum = rand.nextInt((max - min) + 1) + min;
        return randomNum;
    }
}

Answer 1

There are all sorts of problems with your code.

1. You're creating Swing components on the main thread instead of the Event Dispatch Thread. Search for help on this.

2. Have Board subclass JFrame and do the GUI initialization in the constructor or an instance method instead of a static method.

3. Make drawShapes() an instance method.

4. When you create the JPanel , store its reference in an instance variable (eg, myPanel ). This will be easier to do and will be a lot less messy if you fix #2.

5. If you do #2 and #3, just pass the reference to the drawShapes() method.

6. drawShapes() might not even be needed, if all the logic is in the paintComponent() method. Call myPanel.repaint() to invoke the paintComponent() method.

Answer 2

You should use event dispatching to let different JPanels component to act on the event.

eg You could attach a custom event with an event type and jpanel id; and then fire the event from the main. The panel listening to the event do something based on the logic.

Each JPanel listening to the event will intercept the event and if the jpanelid in the event matches to its own jpanel id, it will draw the shape.

I hope you get a pointer.

Here is a sample code, which I have not tested, but it shows how could you use event dispatching/listening to communicate between GUI components.

Define a ChangeEventListener interface

public interface ChangeEventListener {
    public void stateChanged(ChangeEvent e);
}

And define an Event

public class ChangeEvent {

    private Object source;
    private int jPanelId;

    public ChangeEvent(Object source, int jPanelId) {
        this.source = source;
        this.jPanelId= jPanelId;
    }

    public Object getSource() {
        return source;
    }

    public int getJPanelId() {
        return jPanelId;
    }

}

Define your panel like

public class ShapePanel extends JPanel {

private int jPanelId;

private ChangeEventListener changeEventListener;

public void ShapePanel(int jPanelId){
this.jPanelId = jPanelId;
}

/*
.............
.............. Other code
.................
*/

public void addChangeEventListener(ChangeEventListener changeEventListener) {
        this.changeEventListener = changeEventListener;
    }

public int getJPanelId(){
   return jPanelId;
 }

public getChangeEventListener(){
   return changeEventListener;
 }
}

Your main should contain something like;

// Craete different Jpanel
JPanel squareShapePanel = new ShapePanel(1);
JPanel roundShapePanel = new ShapePanel(2);
JPanel triangleShapePanel = new ShapePanel(3);

// Attach event listener with each one like
squareShapePanel.addChangeEventListener(new ChangeEventListener() {
    @Override
    public void stateChanged(ChangeEvent e) {
      if(e.getJPanelId() == squareShapePanel.getJPanelId()){
      // Createshape method can be available inside JPanel code
      // something like squareShapePanel.craeteShape();
      // All in one it is a method which could do something for you on the event.
      // Assuming that it is available in current class
      createShape("square");
    }
});

/*
Similarly attach eventlistener with each panels.
*/
// to draw the square shape, Fire change event
ChangeEvent event = new ChangeEvent(new String("Main"),1);

squareShapePanel.getChangeEventListener().stateChanged(event);

Hope this helps.

Answer 3

Check out Custom Painting Approaches for the two common ways to do custom painting:

1. Keep the Shapes you want to paint in an List and then just paint all the Shapes in the List
2. Use a BufferedImage and just draw the Shapes onto the BufferedImage.

Both examples contain an addRectangle(...) method that allows you to dynamically add a Rectangle to be painted.