解决按下Alt-Gr时JPopupMenu关闭无法输入|的问题

Hi Juliane, sorry to hear you're hitting this frustrating issue with the swingbits table filter popup! Let's walk through some practical solutions to get that vertical bar input working without closing the popup:

• Intercept Popup Key Events to Prevent Closing
  The root problem is likely that the JPopupMenu is interpreting the Alt-Gr press as a trigger to close itself. You can override the popup's key event processing to catch Alt-Gr combinations and keep the popup open while letting the search field handle the input. Here's a quick custom popup implementation:

  class FilterPopupMenu extends JPopupMenu {
      @Override
      protected void processKeyEvent(KeyEvent e) {
          // Check for Alt-Gr modifier (handles cross-system differences)
          if ((e.getModifiersEx() & InputEvent.ALT_GRAPH_DOWN_MASK) != 0) {
              e.consume(); // Stop the popup from reacting to the key
              // Pass the event to the focused search field
              Component focusOwner = getFocusOwner();
              if (focusOwner instanceof JTextField) {
                  ((JTextField) focusOwner).processKeyEvent(e);
              }
              return;
          }
          super.processKeyEvent(e);
      }
  }
  

  You'll need to replace the swingbits filter's default popup with this custom one—check the library's API for methods like setPopupMenu() or similar to inject your implementation.

• Override Search Field Key Bindings
  Sometimes the Alt-Gr key is mapped to a default action that triggers popup closure. Try adding a custom key binding to the filter's search text field to explicitly handle the vertical bar input:

  JTextField searchField = // Get the filter's search field from swingbits
  InputMap inputMap = searchField.getInputMap(JComponent.WHEN_FOCUSED);
  ActionMap actionMap = searchField.getActionMap();
  
  // Map Alt-Gr + | to insert the vertical bar
  inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_BACK_SLASH, InputEvent.ALT_GRAPH_DOWN_MASK), "insertVerticalBar");
  actionMap.put("insertVerticalBar", new AbstractAction() {
      @Override
      public void actionPerformed(ActionEvent e) {
          searchField.insert("|", searchField.getCaretPosition());
      }
  });
  

  This bypasses any default Alt-Gr handling that might be closing the popup, forcing the input to go straight to the text field.

• Adjust Popup Close Triggers
  Swing popups often close when they lose focus or when a non-popup component receives a key press. You can add a PopupMenuListener to the filter popup and modify the close logic:

  popupMenu.addPopupMenuListener(new PopupMenuListener() {
      @Override
      public void popupMenuWillBecomeVisible(PopupMenuEvent e) {}
  
      @Override
      public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
          // Only close if focus is NOT on the search field
          Component focusOwner = KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner();
          if (focusOwner != null && popupMenu.isAncestorOf(focusOwner)) {
              // Cancel the close by requesting focus back to the popup
              popupMenu.requestFocus();
          }
      }
  
      @Override
      public void popupMenuCanceled(PopupMenuEvent e) {}
  });
  

  This checks if the focus is still within the popup (like on the search field) when it tries to close, and cancels the close if so.

• Fallback: Custom Filter Component
  If the library's built-in popup is too rigid, consider replacing the entire filter input component with your own. Create a standalone JTextField with proper Alt-Gr handling, then attach it to the swingbits filter using its extension points—most Swing table filter libraries let you customize the input UI.

内容的提问来源于stack exchange，提问作者Juliane