在Swing中，Enter键无法从组合框中选择元素

问题描述

我已将ItemListener添加到JComboBox。 ItemListener能够使用鼠标单击或空格键检测我所做的任何选择。但它没有识别Enter键。换句话说，如果我使用箭头键滚动ComboBox中的条目然后按Enter键，则不会调用itemStateChanged方法。你有什么想法吗？

I have added an ItemListener to a JComboBox. The ItemListener is able to detect any selection I make using Mouse click or space-bar. But it is not recognizing the Enter Key. In other words, if I use arrow key to scroll through entries in ComboBox and then hit Enter, then the itemStateChanged method is not invoked. Do you have any ideas?

推荐答案

• 从<$ c $收听更改c> MouseEvent 是 ItemListener ，触发 SELECTED / DESELECTED

  用于收听 ENTER键按下 ActionListener

  其他关键事件可以从JComboBox的JList中确定

  rest of key events is possible to determine from JComboBox's JList

  例如

  import java.awt.Component;
  import java.awt.event.*;
  import javax.swing.*;
  import javax.swing.plaf.basic.BasicComboBoxRenderer;
  
  public class ComboBoxHoverOver {
  
      private JComboBox combo = new JComboBox();
  
      public ComboBoxHoverOver() {
          combo.setPrototypeDisplayValue("XXXXXXXXXXXXXXXXXXXXXX");
          combo.setRenderer(new ComboToolTipRenderer(combo));
          combo.addItemListener(new ItemListener() {
  
              @Override
              public void itemStateChanged(ItemEvent e) {
                  System.out.println(combo.getSelectedItem().toString());
              }
          });
          combo.addActionListener(new ActionListener() {
  
              @Override
              public void actionPerformed(ActionEvent e) {
                  System.out.println(combo.getSelectedItem().toString());
              }
          });
          combo.addItem("");
          combo.addItem("Long text 4");
          combo.addItem("Long text 3");
          combo.addItem("Long text 2");
          combo.addItem("Long text 1");
          JFrame f = new JFrame();
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          f.add(combo);
          f.pack();
          f.setVisible(true);
      }
  
      private class ComboToolTipRenderer extends BasicComboBoxRenderer {
  
          private static final long serialVersionUID = 1L;
          private JComboBox combo;
          private JList comboList;
  
          ComboToolTipRenderer(JComboBox combo) {
              this.combo = combo;
          }
  
          @Override
          public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
              super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
              if (comboList == null) {
                  comboList = list;
                  KeyAdapter listener = new KeyAdapter() {
  
                      @Override
                      public void keyReleased(KeyEvent e) {
                          if (e.getKeyCode() == KeyEvent.VK_DOWN || e.getKeyCode() == KeyEvent.VK_UP) {
                              int x = 5;
                              int y = comboList.indexToLocation(comboList.getSelectedIndex()).y;
                              System.out.println(comboList.getSelectedIndex());
                          }
                      }
                  };
                  combo.addKeyListener(listener);
                  combo.getEditor().getEditorComponent().addKeyListener(listener);
              }
              if (isSelected) {
                  System.out.println(value.toString());
              }
              return this;
          }
      }
  
      public static void main(String[] args) {
  
          java.awt.EventQueue.invokeLater(new Runnable() {
  
              @Override
              public void run() {
                  ComboBoxHoverOver comboBoxHoverOver = new ComboBoxHoverOver();
              }
          });
      }
  }
  

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