在JPanel中的每个元素周围添加边框

Question

我有一个JPanel，我在网格的内部添加了25个JPanel。我希望每个面板周围都有一个边框，以便您可以清楚地区分每个元素。填充也可以。我向电路板添加面板的方式如果我尝试添加边框，它将应用于包含元素的较大面板。

public class LightsOutView

{GridLayout实验布局=new GridLayout（5,5）；

// Creates layout of the GUI
public LightsOutView ()
{
    JFrame frame = new JFrame();
    frame.setTitle("Lights Out");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(500, 500);
    frame.setContentPane(makeContents());
    frame.setVisible(true);
}

/**
 * Creates the blank game board. Returns the panel
 * 
 * @return JPanel
 */
public JPanel makeContents ()
{
    // Create a panel to hold the 5x5 grid
    JPanel board = new JPanel(new GridLayout(5, 5));
    board.setLayout(experimentLayout);

    // Add the components to the panel
    for (int i = 0; i < 25; i++)
    {
        board.add(new JPanel()).setBackground(Color.YELLOW);
    }

    // Return the panel
    return board;
}

}

如何在每个元素周围添加边框。是否需要更改将面板添加到网格的方式？

Answer 1

将您的GridLayout更改为如下内容：

GridLayout experimentLayout = new GridLayout(5, 5, gap, gap);

其中gap是一些小的int值，比如1到3（对于像素）。然后给背景容器一个背景色，它将通过间隙显示出来。您还需要为背景JPanel提供具有相同间隙宽度的线条边框。

例如：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.*;

@SuppressWarnings("serial")
public class GridWithBorders extends JPanel {
    private static final int SIDES = 6;
    private static final int SIDE_LENGTH = 60;
    private static final int GAP = 3;
    private static final Color BG = Color.BLACK;
    private static final Color CELL_COLOR = Color.GREEN.darker();

    public GridWithBorders() {
        setBackground(BG);
        setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setLayout(new GridLayout(SIDES, SIDES, GAP, GAP));
        Dimension prefSize = new Dimension(SIDE_LENGTH, SIDE_LENGTH);
        for (int i = 0; i < SIDES; i++) {
            for (int j = 0; j < SIDES; j++) {
                JPanel cell = new JPanel();
                cell.setBackground(CELL_COLOR);
                cell.setPreferredSize(prefSize);
                add(cell);
            }
        }
    }

    private static void createAndShowGui() {
        GridWithBorders mainPanel = new GridWithBorders();

        JFrame frame = new JFrame("GridWithBorders");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}