java - 链接组合框

Question

我正在尝试制作链接的ComboBoxes。例如，我有三个组合框，每个组合框都有三个项目(a、b、c)。在开始时，第一个组合框“a”被选择，第二个组合框“b”被选择，第三个组合框“c”被选择。我需要为它们制作这样的 ActionListener ，其工作方式如下:如果将第二个列表中的选择从“b”更改为“a”，则第一个列表中的所选项目会自动从“a”更改到“b”。

我尝试以这种方式解决问题:

 public class MyComboBoxListener implements ActionListener {

        public void actionPerformed(ActionEvent a) {
            int i = 0;
            int j = 0;
            while (a.getSource() != valsListArray.get(i)) {
                i++;
            }
            String selected = valsListArray.get(i).getSelectedItem().toString();
            while (selected != valsListArray.get(j).getSelectedItem() && j != i) {
                j++;
            }
            String r = chosenVals[i];// in the beginnig elements are that order a, b, c
            valsListArray.get(j).setSelectedItem(chosenVals[i]);
            chosenVals[j] = r;
            chosenVals[i] = selected;
        }
    }

但这并不能解决问题。

Answer 1

你的问题很有趣。一种解决方案是扩展 JComboBox，使其保存对其先前选择的项目和索引的引用，这将允许您在需要时提取信息。例如:

import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;

public class NewComboBox extends JComboBox {
   private Object previousSelectedItem = null;
   private int previousSelectedIndex = -1;

   public Object getPreviousSelectedItem() {
      return previousSelectedItem;
   }

   public int getPreviousSelectedIndex() {
      return previousSelectedIndex;
   }

   NewComboBox(ComboBoxModel aModel) {
      super(aModel);
   }

   @Override
   public void setSelectedIndex(int anIndex) {
      previousSelectedIndex = getSelectedIndex();
      previousSelectedItem = getSelectedItem();
      super.setSelectedIndex(anIndex);
   }

   @Override
   public void setSelectedItem(Object anObject) {
      previousSelectedIndex = getSelectedIndex();
      previousSelectedItem = getSelectedItem();
      super.setSelectedItem(anObject);
   }

}

然后你就可以根据需要使用它了。例如，

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

public class LinkedCombos extends JPanel {
   public static final String[] DATA = {"a", "b", "c"};
   public static final int COMBO_COUNT = 3;
   private DefaultComboBoxModel[] comboModels = new DefaultComboBoxModel[COMBO_COUNT];
   private NewComboBox[] comboBoxes = new NewComboBox[COMBO_COUNT];
   private MyComboListener myComboListener = new MyComboListener();

   public LinkedCombos() {
      for (int i = 0; i < comboModels.length; i++) {
         comboModels[i] = new DefaultComboBoxModel(DATA);
         comboBoxes[i] = new NewComboBox(comboModels[i]);
         comboBoxes[i].setSelectedIndex(i);
         comboBoxes[i].addActionListener(myComboListener);
         add(comboBoxes[i]);
      }
   }

   private class MyComboListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent evt) {
         NewComboBox combo = (NewComboBox) evt.getSource();
         String selection = combo.getSelectedItem().toString();

         for (int i = 0; i < comboBoxes.length; i++) {
            NewComboBox comboI = comboBoxes[i];
            if (comboI != combo && comboI.getSelectedItem().equals(selection)) {
               comboI.setSelectedItem(combo.getPreviousSelectedItem());
            }
         }
      }
   }

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

      JFrame frame = new JFrame("LinkedCombos");
      frame.setDefaultCloseOperation(JFrame.EXIT_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();
         }
      });
   }
}