Java Swing 中 GridLayout 中的 JPanel

Question

每个人。我想在 GridLayout 中有自定义 JPanel（我更喜欢使用绝对位置布局）。 GridLayout 在 ScrollPane 中。

public class App extends JFrame {
    public App() {
        super("bamlOperator");
        JPanel panel = new JPanel(new GridLayout(0, 1));
        JScrollPane scrollPane = new JScrollPane(panel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        setExtendedState(JFrame.MAXIMIZED_BOTH);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        panel.add(new MyCustomPanel());
        panel.add(new MyCustomPanel());
        panel.add(new MyCustomPanel());
        panel.add(new MyCustomPanel());
        panel.add(new MyCustomPanel());
        panel.add(new MyCustomPanel());

        pack();
        setVisible(true);
    }

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

还有我的面板：

public class MyCustomPanel extends JPanel {

    private JLabel aaa = new JLabel("aaa:");
    private JLabel bbb = new JLabel("bbb");
    private JLabel ccc = new JLabel("ccc:");

    public MyCustomPanel() {

        setPreferredSize(new Dimension(100,100));
        JPanel amlPanel = new JPanel();
        amlPanel.setLayout(null);
        amlPanel.setBounds(0,0,100,100);
        aaa.setBounds(10,20,30,40);
        amlPanel.add(aaa);
        bbb.setBounds(20,30,40,50);
        amlPanel.add(bbb);
        ccc.setBounds(30,40,50,60);
        amlPanel.add(ccc);
        add(amlPanel);
    }
}

但它不起作用。

我说，我更喜欢绝对位置布局，但我知道这是不好的做法。我可以使用另一个，但我需要这样的 JPanel：

JPanel 项目

Answer 1

所以，您的根本问题是您将绝对布局与布局管理器混合在一起 - 问题是 MyCustomPanel 没有提供任何尺寸提示，布局管理器可以使用这些提示来更好地决定如何最好地布局您的组件。因此，如果您真的想使用绝对布局，您将不得不完成布局管理 API 为您完成的所有工作

您能告诉我哪个布局管理器最适合我使用吗？

所有这些。不要执着于单一的布局管理器来实现您想要的一切，而是将它们组合在一起以产生您所追求的结果。

我没有您的“确切”要求，但我能够通过使用 BorderLayout 和 GridBagLayout 来实现这一点

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class Test extends JFrame {
    public static void main(String[] args) {
        new Test();
    }

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

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

    public class MainPane extends JPanel {

        public MainPane() {
            // You could use a GridLayout, but GridBagLayout will
            // honour the preferred sizs of each component
            setLayout(new GridBagLayout());
            setBorder(new EmptyBorder(10, 10, 10, 10));
            GridBagConstraints gbc = new GridBagConstraints();
            add(new LeftPane(), gbc);
            add(new MiddleLeftPane(), gbc);
            add(new MiddlePane(), gbc);
            add(new RightPane(), gbc);
        }

    }

    public class LeftPane extends JPanel {

        public LeftPane() {
            setLayout(new GridBagLayout());

            JPanel main = new JPanel(new GridBagLayout());

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.insets = new Insets(4, 4, 4, 4);
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;
            for (int index = 0; index < 6; index++) {
                if (index % 2 == 0) {
                    gbc.anchor = GridBagConstraints.LINE_START;
                } else {
                    gbc.anchor = GridBagConstraints.LINE_END;
                }
                main.add(new JLabel("Label"), gbc);
            }

            gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;
            add(main, gbc);

            gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;
            add(new JButton("Button"));
        }

    }

    public class MiddleLeftPane extends JPanel {

        public MiddleLeftPane() {
            setLayout(new BorderLayout());
            BufferedImage img = new BufferedImage(200, 200, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = img.createGraphics();
            g2d.setColor(Color.RED);
            g2d.drawLine(0, 0, 200, 200);
            g2d.drawLine(200, 0, 0, 200);
            g2d.dispose();

            JLabel label = new JLabel(new ImageIcon(img));
            label.setBorder(new LineBorder(Color.GRAY));
            add(label);
        }

    }

    public class RightPane extends JPanel {

        public RightPane() {
            setLayout(new BorderLayout());
            BufferedImage img = new BufferedImage(200, 200, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = img.createGraphics();
            g2d.setColor(Color.RED);
            g2d.drawLine(0, 0, 200, 200);
            g2d.drawLine(200, 0, 0, 200);
            g2d.dispose();

            JLabel label = new JLabel(new ImageIcon(img));
            label.setBorder(new LineBorder(Color.GRAY));
            add(label);
        }

    }

    public class MiddlePane extends JPanel {

        public MiddlePane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.insets = new Insets(4, 4, 4, 4);

            add(new JButton("Button"), gbc);
            gbc.gridx++;
            add(new JButton("Button"), gbc);

            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy = 2;
            add(new JButton("Button"), gbc);

            gbc.gridy = 1;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;
            add(new JScrollPane(new JTextArea("Text Area", 5, 10)), gbc);
        }

    }
}

Answer 2

您正在使用null 布局来布局自定义面板。当您将其添加到另一个网格布局面板中时，由于未设置大小，因此不会绘制。尝试为您的自定义面板使用适当的布局。 并且，请参阅Using a JPanel with a null layout 的答案。