java - 尝试使用 Eclipse WindowBuilder，但 ActionLister 没有执行任何操作

Question

我已尝试查看大约 5 个不同的 WindowBuilder 教程，虽然在测试代码时可以显示应用程序窗口，但无法使按钮正常工作。这是我根据我看过的教程编写的代码。

package guiTest;

import java.awt.EventQueue;

import javax.swing.JFrame;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import java.awt.GridBagConstraints;
import javax.swing.JLabel;
import java.awt.Insets;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class GuiTest {

    private JFrame frame;

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

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

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridBagLayout gridBagLayout = new GridBagLayout();
        gridBagLayout.columnWidths = new int[]{0, 0, 0, 0, 0, 0, 0, 0};
        gridBagLayout.rowHeights = new int[]{0, 0, 0, 0, 0, 0};
        gridBagLayout.columnWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
        gridBagLayout.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
        frame.getContentPane().setLayout(gridBagLayout);

        JButton btnLabelAdd = new JButton("Label Add");
        GridBagConstraints gbc_btnLabelAdd = new GridBagConstraints();
        gbc_btnLabelAdd.insets = new Insets(0, 0, 5, 0);
        gbc_btnLabelAdd.gridx = 6;
        gbc_btnLabelAdd.gridy = 1;
        frame.getContentPane().add(btnLabelAdd, gbc_btnLabelAdd);
        btnLabelAdd.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent evt) {
                makeLabel(evt);
            }
        });
    }

    private void makeLabel(ActionEvent evt) {
        JLabel lblHereLabel = new JLabel("Here Label");
        GridBagConstraints gbc_lblHereLabel = new GridBagConstraints();
        gbc_lblHereLabel.gridx = 6;
        gbc_lblHereLabel.gridy = 4;
        frame.getContentPane().add(lblHereLabel, gbc_lblHereLabel);
    }
}

有人有任何技巧可以让它发挥作用吗？或者我可以使用一些示例代码来确保问题不在于 Eclipse？我在这里假设按钮应该在左键单击时制作标签；这是正确的吗？

Answer 1

你的按钮工作正常。您可以在调试器中观看代码跳转到 makeLabel() 中。您只是没有让新标签可见。

正如 @MadProgrammer 所建议的，添加新标签后，您可以通过调用 revalidate() 告诉封闭的 Container 进行自身更新，然后 repaint() 以使其重绘自身:

private void makeLabel(ActionEvent evt) {
    JLabel lblHereLabel = new JLabel("Here Label");
    GridBagConstraints gbc_lblHereLabel = new GridBagConstraints();
    gbc_lblHereLabel.gridx = 6;
    gbc_lblHereLabel.gridy = 4;
    frame.getContentPane().add(lblHereLabel, gbc_lblHereLabel);
    frame.getContentPane().revalidate();
    frame.getContentPane().repaint();
}

这样做意味着您不再需要直接访问 frame。这意味着您可以通过查询为其所属的 Container 触发事件的按钮来将处理程序重写为“与框架无关”，然后只需向其添加新标签，如下所示:

private void makeLabel(ActionEvent evt) {
    JLabel lblHereLabel = new JLabel("Here Label");
    GridBagConstraints gbc_lblHereLabel = new GridBagConstraints();
    gbc_lblHereLabel.gridx = 6;
    gbc_lblHereLabel.gridy = 4;

    Container displayArea = ((JButton) evt.getSource()).getParent();
    displayArea.add(lblHereLabel, gbc_lblHereLabel);
    displayArea.revalidate();
    displayArea.repaint();
}