java为什么JFrame是透明的？

Question

我的JFrame坏了。如果我只是将JFrame设置为visible，那么整个JFrame就会出现，但如果我在将JFrame设置为visible之后尝试执行任何操作，那么JFrame就会出现，但它是透明的，只有标题和关闭选项可见。这只是最近才发生的事，我不知道发生了什么

可见JFrame

GUI frame = new GUI(); //GUI is a class that extends JFrame
frame.setVisible(true);

透明JFrame

GUI frame = new GUI(); //GUI is a class that extends JFrame
frame.setVisible(true);
frame.setVisible(false); //If I throw a breakpoint here, as soon as it goes from .setVisible(true) to this line, the GUI appears, but is transparent

代码

public class GUI extends JFrame {
private JPanel contentPane;

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                GUI frame = new GUI();
                frame.setVisible(true);
                frame.setVisible(false);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

public GUI() {
    setTitle("Title");
    setResizable(false);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 330, 250);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    contentPane.setLayout(new BorderLayout(0, 0));
    setContentPane(contentPane);
}

}

图像

Answer 1

问题可能在于：

frame.setVisible(false); // If I throw a breakpoint here, as soon as it goes from 
                         // .setVisible(true) to this line, the GUI appears, 
                         // but is transparent

通过在运行Swing代码时设置断点，可以阻止Swing事件线程，从而阻止GUI绘制或与用户交互。解决方法是，如果需要在GUI运行时对其进行调试，可以尝试不同的方法，包括使用记录器记录程序运行时的状态

---

编辑
你在评论中说：

I want the user to finish selecting their settings before the applications proceeds forward. So I am not actually using a while(true), but a while(visible). visible is a boolean that is set to false when the user clicks on a button on the gui, which will break out of the loop.

然后，解决方案就完全不同了，而且非常简单：不要使用第二个JFrame来显示这个设置显示窗口，而是希望使用模式JDialog或JOptionPane（实际上只不过是一个专门的模式JDialog）

这之所以有帮助，是因为Swing为模式对话框提供了一种特殊机制，在设置对话框可见后，它会立即冻结调用窗口中的代码流。因此，调用代码将始终知道对话框何时不再可见，因为只有当对话框不可见时，其代码的程序流才会恢复。因此，您可能希望在设置对话框或JOptionPane可见的行后面的行中提取对话框窗口的数据。在你认为JOptionPanes过于简单之前，请理解它们的第二个参数，即Object类型的参数可以将任何Swing GUI组件作为参数，包括一个包含非常大和复杂GUI的JPanel，这使得这些工具非常有用

---

编辑2
你在评论中说：

I am using WindowsBuilder for my GUI related things to make things easier for me. Unfortunately, it doesn't offer the option to use JOptionPane. There are no JDialogue, too. I want to stay on the route that WindowsBuilder will be able to modify.

在理解底层库之前，我不会讨论为什么避免使用代码生成工具很重要，。。。但我建议您检查WindowBuilder工具是否提供了创建扩展JPanel的类的选项。如果是这样，那么就这样做，创建您的JPanel，然后在调用代码中，只需将您的JPanel填充到JOptionPane或modal JDialog中

---

编辑3

例如，假设您有一个名为GetInfoPanel的JPanel，它允许用户输入一些文本并选择一个JRadioButton：

class GetInfoPanel extends JPanel {
   public static final String[] COLOR_STRINGS = {"Red", "Green", "Blue", "Orange"};
   private JTextField infoField = new JTextField(10);
   private ButtonGroup buttonGroup = new ButtonGroup();

   public GetInfoPanel() {
      JPanel topPanel = new JPanel();
      topPanel.add(new JLabel("Information that you want to submit:"));
      topPanel.add(infoField);

      JPanel colorPanel = new JPanel(new GridLayout(1, 0, 5, 0));
      for (String colorString : COLOR_STRINGS) {
         JRadioButton radioButton = new JRadioButton(colorString);
         radioButton.setActionCommand(colorString);
         buttonGroup.add(radioButton);
         colorPanel.add(radioButton);
      }


      setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
      add(topPanel);
      add(colorPanel);
   }

   public String getInfo() {
      return infoField.getText();
   }

   public String getColorString() {
      String selection = "";
      ButtonModel model = buttonGroup.getSelection();
      if (model != null) {
         selection = model.getActionCommand();
      }

      return selection;
   }
}

然后，调用类可以创建上面的实例，并将其打包并显示在JOptionPane中，然后提取其中包含的信息：

  public void actionPerformed(ActionEvent e) {
     // create our GetInfoPanel
     GetInfoPanel getInfoPanel = new GetInfoPanel();

     // display it in a JOptionPane which is a modal JDialog
     JOptionPane.showMessageDialog(TestGetInfo.this, getInfoPanel,
           "Enter Information Please", JOptionPane.PLAIN_MESSAGE);

     // this code will not be called until the dialog above is no longer visible
     // extract the text from the getInfoPanel's text field 
     String info = getInfoPanel.getInfo();
     infoDisplayField.setText(info);

     // extract the the radiobutton selection from the getInfoPanel
     String colorString = getInfoPanel.getColorString();
     colorStringField.setText(colorString);
  }

你可以在这个程序中自己测试：

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

@SuppressWarnings("serial")
public class TestGetInfo extends JPanel {
   private JTextField infoDisplayField = new JTextField(10);
   private JTextField colorStringField = new JTextField(10);
   private JButton displayGetInfoBtn = new JButton(new DisplayGetInfoAction(
         "Get Info"));

   public TestGetInfo() {
      infoDisplayField.setFocusable(false);
      colorStringField.setFocusable(false);

      add(new JLabel("Info:"));
      add(infoDisplayField);
      add(Box.createHorizontalStrut(10));
      add(new JLabel("Color:"));
      add(colorStringField);
      add(Box.createHorizontalStrut(10));
      add(displayGetInfoBtn);
   }

   private class DisplayGetInfoAction extends AbstractAction {
      public DisplayGetInfoAction(String name) {
         // this will be the button's text:
         super(name);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         // create our GetInfoPanel
         GetInfoPanel getInfoPanel = new GetInfoPanel();

         // display it in a JOptionPane which is a modal JDialog
         JOptionPane.showMessageDialog(TestGetInfo.this, getInfoPanel,
               "Enter Information Please", JOptionPane.PLAIN_MESSAGE);

         // this code will not be called until the dialog above is no longer visible
         // extract the text from the getInfoPanel's text field 
         String info = getInfoPanel.getInfo();
         infoDisplayField.setText(info);

         // extract the the radiobutton selection from the getInfoPanel
         String colorString = getInfoPanel.getColorString();
         colorStringField.setText(colorString);
      }
   }

   private static void createAndShowGui() {
      TestGetInfo mainPanel = new TestGetInfo();

      JFrame frame = new JFrame("TestGetInfo");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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

@SuppressWarnings("serial")
class GetInfoPanel extends JPanel {
   public static final String[] COLOR_STRINGS = {"Red", "Green", "Blue", "Orange"};
   private JTextField infoField = new JTextField(10);
   private ButtonGroup buttonGroup = new ButtonGroup();

   public GetInfoPanel() {
      JPanel topPanel = new JPanel();
      topPanel.add(new JLabel("Information that you want to submit:"));
      topPanel.add(infoField);

      JPanel colorPanel = new JPanel(new GridLayout(1, 0, 5, 0));
      for (String colorString : COLOR_STRINGS) {
         JRadioButton radioButton = new JRadioButton(colorString);
         radioButton.setActionCommand(colorString);
         buttonGroup.add(radioButton);
         colorPanel.add(radioButton);
      }


      setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
      add(topPanel);
      add(colorPanel);
   }

   public String getInfo() {
      return infoField.getText();
   }

   public String getColorString() {
      String selection = "";
      ButtonModel model = buttonGroup.getSelection();
      if (model != null) {
         selection = model.getActionCommand();
      }

      return selection;
   }
}