java - 为什么 JFrame 是透明的？

Question

我有一个正在运行的 JFrame。如果我只是将 JFrame 设置为可见，则会显示整个 JFrame，但如果我在将 JFrame 设置为可见后尝试执行任何操作，则 JFrame 将出现，但它是透明的，只有标题和关闭选项可见。这是最近才发生的，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);
}

图片

Answer 1

问题可能出在这里:

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，您可以阻止 Swing 事件线程，从而阻止 GUI 绘制或与用户交互。如果您需要在 GUI 运行时调试它，则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。

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编辑
您在评论中声明:

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.

那么解决方案就完全不同而且非常简单:不要使用第二个 JFrame 来显示此设置显示窗口，而是您需要使用 modal JDialog 或 JOptionPane(这实际上是只不过是一个专门的模态 JDialog。

之所以有帮助，是因为 Swing 有一种用于模态对话框的特殊机制，它在将对话框设置为可见后立即卡住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，因为其代码的程序流仅在对话框不可见时才会恢复。因此，您可能希望在设置对话框或 JOptionPane 可见的行之后立即提取对话窗口的数据。在您因为过于简单而放弃 JOptionPanes 之前，请了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，包括一个拥有非常大且复杂的 GUI 的 JPanel，这使得这些工具非常有用。

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编辑2
您在评论中声明:

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.

在您了解底层库之前，我不会大谈特谈为什么避免使用代码生成工具很重要，...但我确实建议您检查 WindowBuilder 工具是否为您提供了该选项创建一个扩展 JPanel 的类。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 或模态 JDialog 中。

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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;
   }
}