painting a particular button from a grid of buttons

问题

The following grid of buttons is defined as :

JButton button_x = new RoundButton();

where RoundButton is defined as :

public class RoundButton extends JButton {

    public RoundButton(String label) {
        super(label);
        this.setContentAreaFilled(false);
        Dimension size = this.getPreferredSize();
        size.height = size.width = Math.max(size.height, size.width);
        this.setPreferredSize(size);
    }

    @Override
    protected void paintComponent(Graphics g) {
        if(!GameState.getIfComplete()) { // If the game is not complete or has just started
            this.setBorder(null);
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, this.getSize().width, this.getSize().height);
            if(this.getModel().isArmed()) {
               g.setColor(Color.RED);
            }else {
                g.setColor(Color.GREEN);
            }
            g.fillOval(0,0,this.getSize().width-1,this.getSize().height-1);
            super.paintComponent(g);
        }else {
            this.setBorder(null);
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, this.getSize().width, this.getSize().height);
            g.setColor(Color.WHITE);
            g.fillOval(0,0,this.getSize().width-1,this.getSize().height-1);
            super.paintComponent(g); 
        }
    }

}

Currently all the buttons are painted in green, but on a certain condition I want to paint particular buttons in white (which is the code in the else part).For instance when !GameState.getIfComplete() returns false I want to paint the buttons in the first column in white. So I call repaint as :

buttons[0].repaint();
buttons[3].repaint();
buttons[6].repaint();

But this doesn't work ! With the first column some other buttons are also painted in white. Why is that ?

What is wrong with the call ? How do I paint a particular button ?

回答1:

The problem is the reliance on the GameState, ALL your round buttons use the same logic to paint themselves, that is, when the game is completed, they will all be painted WHITE

Instead, you should rely on the properties of the button. Set it up so that the colors are actually derived from the button itself.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class BadButton01 {

    public static void main(String[] args) {
        new BadButton01();
    }

    public BadButton01() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public static class GameState {

        private static boolean isComplete;

        public static boolean getIfComplete() {
            return isComplete;
        }

        public static void setComplete(boolean value) {
            isComplete = value;
        }

    }

    public class TestPane extends JPanel {

        private RoundButton[] btns = new RoundButton[]
        {
            new RoundButton("1"),
            new RoundButton("2"),
            new RoundButton("3"),
            new RoundButton("4"),
            new RoundButton("5"),
            new RoundButton("6"),
            new RoundButton("7"),
            new RoundButton("8"),
            new RoundButton("9")
        };

        public TestPane() {
            setLayout(new GridLayout(3, 3));
            for (RoundButton btn : btns) {
                add(btn);
            }
            btns[0].addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    GameState.setComplete(true);
                    btns[0].setBackground(Color.WHITE);
                    btns[1].setBackground(Color.WHITE);
                    btns[2].setBackground(Color.WHITE);
                    repaint();
                }
            });
        }

    }

    public class RoundButton extends JButton {

        public RoundButton(String label) {
            super(label);
            this.setContentAreaFilled(false);
            setBorderPainted(false);
            setFocusPainted(false);
            setOpaque(false);
            Dimension size = this.getPreferredSize();
            size.height = size.width = Math.max(size.height, size.width);
            this.setPreferredSize(size);
            setBackground(Color.GREEN);
        }

        @Override
        protected void paintComponent(Graphics g) {
//            if (!GameState.getIfComplete()) { // If the game is not complete or has just started
//                this.setBorder(null);
//                g.setColor(Color.BLACK);
//                g.fillRect(0, 0, this.getSize().width, this.getSize().height);
                if (this.getModel().isArmed()) {
                    g.setColor(Color.RED);
                } else {
//                    g.setColor(Color.GREEN);
                    g.setColor(getBackground());
                }
//            } else {
//                this.setBorder(null);
//                g.setColor(Color.BLACK);
//                g.fillRect(0, 0, this.getSize().width, this.getSize().height);
//                g.setColor(Color.WHITE);
//                g.fillOval(0, 0, this.getSize().width - 1, this.getSize().height - 1);
//                g.setColor(getBackground());
//            }
            g.fillOval(0, 0, this.getSize().width - 1, this.getSize().height - 1);
            super.paintComponent(g);
        }

    }

}

来源：https://stackoverflow.com/questions/15846937/painting-a-particular-button-from-a-grid-of-buttons