java - JPanel 上 JLabel 的定位

Question

我正在手动编写 GUI，但在 JPanel 上定位 JLabel 时遇到了困难。我试图将其放在 JTextField 上方的左上角，但即使我设置了边界，它也默认位于中间:

相关代码:

JPanel mainPanel = new JPanel();

JLabel myFleetLabel = new JLabel("My Fleet");
myFleetLabel.setBounds(1,1, 10, 10);

mainPanel.add(myFleetLabel);

add(mainPanel);

它看起来像这样:

Answer 1

有几种方法可以实现此目的，例如，一种可能是使用 GridBagLayout 作为主要布局管理器

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
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;

public class Test {

    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 TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.NORTHWEST;
            JLabel label = new JLabel("My Fleet: ");
            add(label, gbc);

            JTextArea ta = new JTextArea(10, 20);
            gbc.gridx++;
            add(new JScrollPane(ta), gbc);

            gbc.gridx = 0;
            gbc.gridy++;
            gbc.gridwidth = 2;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            add(new JScrollPane(new JTextArea(5, 10)), gbc);

            JPanel actions = new JPanel();
            actions.add(new JButton("Create Ship"));
            actions.add(new JButton("Flip Coins"));

            gbc.gridy++;
            add(actions, gbc);
        }

    }

}

参见Laying Out Components Within a Container和 How to Use GridBagLayout了解更多详情。

请记住，单个布局管理器不太可能解决您的所有问题，有时您需要使用两个或多个布局管理器来完成整体效果