jDialog未显示

Question

我尝试将我的jPanel添加到jDialog中，当我触发按钮时，什么都不会发生。为什么？我有下面的代码: public class fontFormat{

public void fontPanel(){

    JPanel panel = new JPanel();
    panel.setLayout(new FlowLayout());

    panel.getPreferredSize();
    Dimension size = new Dimension();

    size.width = 400;
    size.height = 600;

    panel.setPreferredSize(size);

    panel.add(new JLabel("label"));
    panel.add(new JButton("button"));


    JDialog fontDialog = new JDialog();

    fontDialog.add(fontDialog);
 }
}

Answer 1

在此：

JDialog fontDialog = new JDialog();
fontDialog.add(fontDialog);

您似乎试图将您的JDialog添加到自身，这应该会导致您的代码不起作用。虽然这段代码可以编译，但是运行此方法应该会导致JVM在fontDialog.add(fontDialog);行上抛出一个fontDialog.add(fontDialog);。

请注意，您显示的JDialog与显示JFrame的方式类似：

• 当您调用您的JDialog构造函数时，您将希望将父窗口传递到它，特别是如果您希望显示一个模态对话框。
• 您还需要将正确的ModalityType枚举传递给构造函数。
• 给出JDialog内容，通常是一个包含组件的JPanel。
• 你把它打包
• 然后在上面调用setVisible(true)，它应该显示

例如,

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class DialogEg {
   private static void createAndShowGUI() {
      MainPanelGen mainPanelGen = new MainPanelGen();

      JFrame frame = new JFrame("DialogEg");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanelGen.getMainPanel());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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

}

class MainPanelGen {
   private JPanel mainPanel = new JPanel();
   private JTextField field = new JTextField(10);
   private JButton btn = new JButton(new BtnActn());
   private JDialog dialog;
   private DialogPanel dialogPanel = new DialogPanel();

   public MainPanelGen() {
      mainPanel.add(field);
      mainPanel.add(btn);

      field.setEditable(false);
      field.setFocusable(false);
   }

   public JPanel getMainPanel() {
      return mainPanel;
   }

   private class BtnActn extends AbstractAction {
      BtnActn() {
         super("Button");
      }

      @Override
      public void actionPerformed(ActionEvent arg0) {
         if (dialog == null) {
            Window win = SwingUtilities.getWindowAncestor(mainPanel);
            if (win != null) {
               dialog = new JDialog(win, "My Dialog",
                     Dialog.ModalityType.APPLICATION_MODAL);
               dialog.getContentPane().add(dialogPanel);
               dialog.pack();
               dialog.setLocationRelativeTo(null);
            }
         }
         dialog.setVisible(true); // here the modal dialog takes over
         System.out.println   (dialogPanel.getFieldText());
         field.setText(dialogPanel.getFieldText());
      }
   }
}

class DialogPanel extends JPanel {
   private JTextField field = new JTextField(10);
   private JButton exitBtn = new JButton(new ExitBtnAxn("Exit"));

   public DialogPanel() {
      add(field);
      add(exitBtn);
   }

   public String getFieldText() {
      return field.getText();
   }

   private class ExitBtnAxn extends AbstractAction {

      public ExitBtnAxn(String name) {
         super(name);
      }

      @Override
      public void actionPerformed(ActionEvent arg0) {
         Window win = SwingUtilities.getWindowAncestor(DialogPanel.this);
         if (win != null) {
            win.dispose();
         }

      }
   }
}