动态的Jcomboboxes

Question

我有以下数据（字符串）：

Course1: A1
Course1: A2
Course2: B1
Course2: B2
Course2: B3
Course2: B4
Course3: C1
Course3: C2

我想创建两个 Jcombobox （JCOMBOBOX1，JCOMBOBOX2），因此Jcombobox1包含Course1，Course2，Course3，等。

如果我从Jcombobox1中选择课程2，则应在JCombobox2中填充相应的B1，B2，B3，B4。

如何实施？非常感谢。

Answer 1

是的，只需创建一个 DefaultComboBoxModel 对于每组，做 setModel() 在 JComboBox2 什么时候 JComboBox1 变化。

附录：例如，

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ComboTest extends JPanel implements ActionListener, Runnable {

    private final JComboBox combo1 = new JComboBox(
        new String[]{"Course 1", "Course 2", "Course 3"});
    private final JComboBox combo2 = new JComboBox();
    private ComboBoxModel[] models = new ComboBoxModel[3];

    public ComboTest() {
        models[0] = new DefaultComboBoxModel(
            new String[]{"A1", "A2"});
        models[1] = new DefaultComboBoxModel(
            new String[]{"B1", "B2", "B3", "B4"});
        models[2] = new DefaultComboBoxModel(
            new String[]{"C1", "C2"});

        combo2.setModel(models[0]);
        this.add(combo1);
        this.add(combo2);
        combo1.addActionListener(this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        int i = combo1.getSelectedIndex();
        combo2.setModel(models[i]);
    }

    @Override
    public void run() {
        JFrame f = new JFrame("ComboTest");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new ComboTest());
    }
}

Answer 2

是的。您可以将更改事件侦听器添加到更新第二个Jcombobox值的第一个JCOMBOBOX。

这样的东西

// first comboBox
final JComboBox courseBox = new JComboBox(
                               new String[]{"Course 1", "Course 2", "Course 3"});

final JComboBox box2 = new JComboBox();

// Now listen for changes
courseBox.addActionListener(new ActionListener(){
   void actionPerformed(ActionEvent e){
       if(courseBox.getSelectedItem().equals("Course 1")){
           // we know that the user picked "Course 1", now change box2 to match
           // first clear everything
           box2.removeAllItems();
           // now add back relevant values
           box2.addItem("A1");
           box2.addItem("A2");
       }else if(...){
           // ...
       }
   }
});