java paintComponent（graphics g）无法正常工作

Question

I'm trying to paint a simple rectangle, but it won't work. My sout in paintComponent tells me that it gets inside of paintComponent. I've googled it for some hours now but I can't find what I'm doing wrong. The paintComponent is in a class that extends JComponent, as it should. I call super.paintComponent(g), not super.paintComponent s (g) and soo on. What am I missing?

import java.awt.*;
import javax.swing.*;
public class Board extends JComponent{
    private GameCreator game;
    public Board(GameCreator game)
    {
        this.game = game;
    }

    @Override
    public void paintComponent (Graphics g){
        super.paintComponent(g);
        g.fillRect(50,50,300,300);
        g.setColor(Color.orange);
        System.out.println("inside piantComponent");
    }

    public static void main(String[]args)
    {
        GameCreator game = new GameCreator(8,10);
        game.prepareBoard();
        Board board = new Board(game);
        new Frame("test", board);
    }
}




import javax.swing.*;
import java.awt.*;
public class Frame extends JFrame {
    Board board;
    JPanel gamePanel;

    public Frame(String title, Board board) {
        super(title);
        setLayout(new BorderLayout());
        setPreferredSize(new Dimension(800, 800));
        pack();
        setVisible(true);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        this.board = board;
        gamePanel = new JPanel();
        gamePanel.add(board);
        setContentPane(gamePanel);

    }
}

Answer 1

Your board does not have a size. Set it with setPrefferedSize. Also you have to call g.setColor before fillRect.