java - JLabel:手动设置PreferredSize，但在setText之后获取PreferredSize

Question

我想通过 setPreferredSize() 将 JLabel 的大小设置为特定(最小)大小。 如果 JLabel 内的文本不再适合，则 JLabel 应该增大。

现在的问题是:

• 之后label.setPreferredSize(new Dimension(50,20));
• 我这样做setText("new long text");但大小不会改变

import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

public class LabelTest
{
    public static void createWindow()
    {
        JFrame frame = new JFrame();

        JLabel label = new JLabel("Text");
        System.out.println(label.getPreferredSize().width); // 25
        label.setText("New long text");
        System.out.println(label.getPreferredSize().width); // 77 - JLabel grows as expected

        label.setText("Text");
        System.out.println(label.getPreferredSize().width); // 25
        label.setPreferredSize(new Dimension(50, 20));
        System.out.println(label.getPreferredSize().width); // 50 - JLabel grows to given size as expected
        label.setText("New long text");
        System.out.println(label.getPreferredSize().width); // 50 - it should be 77 again

        frame.add(label);
        frame.setPreferredSize(new Dimension(200, 100));
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    }


    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                createWindow();
            }
        });
    }
}

所以我需要一个解决方案来在我手动设置首选尺寸后设置文本时获取新的首选尺寸。

如果您需要更多信息，请询问。

提前致谢!

Answer 1

您可以使用 LayoutManager 达到您想要的效果
下面是 GridBag 布局的示例

public class GridBagExample extends JFrame {

    private JPanel      contentPane;
    private JLabel      lblMyLabel;
    private JTextField  textField;
    private JButton     btnChangeMyLabel;

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

    /**
     * Create the frame.
     */
    public GridBagExample() {
        initComponents();
    }

    private void initComponents() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 94);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        GridBagLayout gbl_contentPane = new GridBagLayout();
        gbl_contentPane.columnWidths = new int[] { 0, 344, 0 };
        gbl_contentPane.rowHeights = new int[] { 0, 0, 0 };
        gbl_contentPane.columnWeights = new double[] { 0.0, 1.0, Double.MIN_VALUE };
        gbl_contentPane.rowWeights = new double[] { 1.0, 1.0, Double.MIN_VALUE };
        contentPane.setLayout(gbl_contentPane);

        lblMyLabel = new JLabel(" My Label");
        GridBagConstraints gbc_lblMyLabel = new GridBagConstraints();
        gbc_lblMyLabel.insets = new Insets(0, 0, 5, 5);
        gbc_lblMyLabel.anchor = GridBagConstraints.EAST;
        gbc_lblMyLabel.gridx = 0;
        gbc_lblMyLabel.gridy = 0;
        contentPane.add(lblMyLabel, gbc_lblMyLabel);

        textField = new JTextField();
        GridBagConstraints gbc_textField = new GridBagConstraints();
        gbc_textField.insets = new Insets(0, 0, 5, 0);
        gbc_textField.fill = GridBagConstraints.HORIZONTAL;
        gbc_textField.gridx = 1;
        gbc_textField.gridy = 0;
        contentPane.add(textField, gbc_textField);
        textField.setColumns(10);

        btnChangeMyLabel = new JButton("Change My Label");
        btnChangeMyLabel.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                lblMyLabel.setText("This is the new text of my JLabel");
            }
        });
        GridBagConstraints gbc_btnChangeMyLabel = new GridBagConstraints();
        gbc_btnChangeMyLabel.gridwidth = 2;
        gbc_btnChangeMyLabel.gridx = 0;
        gbc_btnChangeMyLabel.gridy = 1;
        contentPane.add(btnChangeMyLabel, gbc_btnChangeMyLabel);
    }

希望有帮助。