如何為添加到JFrame的JPanel添加邊框？

Question

我有一個Java swing應用程序，它具有一個名為GPanel的嵌套類，該類擴展了JPanel。

GPanel的實例（名為graphicsPanel）被添加到帶有GridBagLayout的JFrame中。

致電之前

frame.getContentPane().add(graphicsPanel);

我打電話

graphicsPanel.setBorder(MyWindow.GRAPHICS_BORDER);

注意：

private static final Border GRAPHICS_BORDER = BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10), BorderFactory.createLineBorder(Color.BLACK, 1));

但是，邊框不會出現。

我希望邊框出現在GPanel周圍。

下面是完整的代碼：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridBagLayout;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.Border;

public class MyWindow {

    //virtual pixels
    private static boolean[][] screenPixels = {

        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true}

    };

    //this is the border i want around my GPanel
    private static final Border GRAPHICS_BORDER = BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10), BorderFactory.createLineBorder(Color.BLACK, 1));

    //this is the size of the checkerboard inside the GPanel
    private static int dimension = 200;

    private JFrame frame;
    private GPanel graphicsPanel;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MyWindow window = new MyWindow();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public MyWindow() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {

        frame = new JFrame();
        frame.setTitle("Alexander Fisher's Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(new GridBagLayout());
        frame.setResizable(false);

        graphicsPanel = new GPanel();
        //this is where i try to set the border
        graphicsPanel.setBorder(MyWindow.GRAPHICS_BORDER);
        graphicsPanel.setPreferredSize(new Dimension(MyWindow.dimension, MyWindow.dimension));
        graphicsPanel.setMinimumSize(new Dimension(MyWindow.dimension, MyWindow.dimension));
        graphicsPanel.setMaximumSize(new Dimension(MyWindow.dimension, MyWindow.dimension));
        frame.getContentPane().add(graphicsPanel);
        frame.pack();

    }

    private class GPanel extends JPanel {
        /**
         * 
         */
        private static final long serialVersionUID = 1L;

        @Override
        public void paint(Graphics g) {

            int pixelDimension = MyWindow.dimension / MyWindow.screenPixels.length;

            for(int intRowIndex = 0; intRowIndex < MyWindow.screenPixels.length; intRowIndex++) {
                for(int intColumnIndex = 0; intColumnIndex < MyWindow.screenPixels.length; intColumnIndex++) {
                    if(!MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                        g.setColor(Color.WHITE);
                        g.fillRect(intRowIndex * pixelDimension, intColumnIndex * pixelDimension, pixelDimension, pixelDimension);
                    } else if(MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                        g.setColor(Color.BLACK);
                        g.fillRect(intRowIndex * pixelDimension, intColumnIndex * pixelDimension, pixelDimension, pixelDimension);
                    }
                }
            }


        }
    }

}

編輯（解決）：

我添加了一行：

 private static final int BORDER_WIDTH = 11;

到MyWindow類的變量，因為部分問題是我正在繪制邊框的頂部繪制。 除了此更改之外，我還更新了MyWindow.gameDimension變量用於說明邊框寬度的任何地方。

接下來，我將覆蓋paint（Graphics g）方法的方法更改為一個覆蓋paintComponent（Graphics g）方法的方法，確保首先調用super.paintComponent（Graphics g）。 @MadProgrammer的建議

public void paintComponent(Graphics g) {
    super.paintComponent(g);//added this line

    int pixelDimension = MyWindow.dimension / MyWindow.screenPixels.length;

    for(int intRowIndex = 0; intRowIndex < MyWindow.screenPixels.length; intRowIndex++) {
        for(int intColumnIndex = 0; intColumnIndex < MyWindow.screenPixels.length; intColumnIndex++) {
            if(!MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                g.setColor(Color.WHITE);
                g.fillRect(intRowIndex * pixelDimension + MyWindow.BORDER_WIDTH, intColumnIndex * pixelDimension + MyWindow.BORDER_WIDTH, pixelDimension, pixelDimension);
            } else if(MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                g.setColor(Color.BLACK);
                g.fillRect(intRowIndex * pixelDimension + MyWindow.BORDER_WIDTH, intColumnIndex * pixelDimension + MyWindow.BORDER_WIDTH, pixelDimension, pixelDimension);
            }

        }

    }

}

編輯代碼：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridBagLayout;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.Border;

public class MyWindow {

    //virtual pixels
    private static boolean[][] screenPixels = {

        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true},
        {true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false},
        {false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true, false, true}

    };

    //this is the border i want around my GPanel
    private static final Border GRAPHICS_BORDER = BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10), BorderFactory.createLineBorder(Color.BLACK, 1));

    //this is the size of the colored square inside the border
    private static int dimension = 200;
    private static final int BORDER_WIDTH = 11;

    private JFrame frame;
    private GPanel graphicsPanel;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MyWindow window = new MyWindow();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public MyWindow() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {

        frame = new JFrame();
        frame.setTitle("Alexander Fisher's Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(new GridBagLayout());
        frame.setResizable(false);

        graphicsPanel = new GPanel();
        graphicsPanel.setBorder(MyWindow.GRAPHICS_BORDER);
        graphicsPanel.setPreferredSize(new Dimension(MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH, MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH));
        graphicsPanel.setMinimumSize(new Dimension(MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH, MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH));
        graphicsPanel.setMaximumSize(new Dimension(MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH, MyWindow.dimension + 2 * MyWindow.BORDER_WIDTH));
        frame.add(graphicsPanel);
        frame.pack();

    }

    private class GPanel extends JPanel {
        /**
         * 
         */
        private static final long serialVersionUID = 1L;

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            int pixelDimension = MyWindow.dimension / MyWindow.screenPixels.length;

            for(int intRowIndex = 0; intRowIndex < MyWindow.screenPixels.length; intRowIndex++) {
                for(int intColumnIndex = 0; intColumnIndex < MyWindow.screenPixels.length; intColumnIndex++) {
                    if(!MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                        g.setColor(Color.WHITE);
                        g.fillRect(intRowIndex * pixelDimension + MyWindow.BORDER_WIDTH, intColumnIndex * pixelDimension + MyWindow.BORDER_WIDTH, pixelDimension, pixelDimension);
                    } else if(MyWindow.screenPixels[intRowIndex][intColumnIndex]) {
                        g.setColor(Color.BLACK);
                        g.fillRect(intRowIndex * pixelDimension + MyWindow.BORDER_WIDTH, intColumnIndex * pixelDimension + MyWindow.BORDER_WIDTH, pixelDimension, pixelDimension);
                    }
                }
            }


        }
    }

}

Answer 1

問題

public void paint(Graphics g) { ...這是您的關鍵問題

如果您仔細查看執行自定義繪畫

javax.swing.JComponent擴展了此類，並進一步將paint方法分解為三個單獨的方法，並按以下順序調用：

• 受保護的void paintComponent（Graphics g）
• 受保護的void paintBorder（Graphics g）
• 受保護的void paintChildren（圖形g）

因此，通過覆蓋paint並且不遵守現有的油漆鏈，可以防止對邊界進行油漆。

解決方案

根據執行自定義繪畫的建議，您應該改寫paintComponent （並在執行任何自定義繪畫之前調用super.paintComponent ）