JComboBox操作侦听器

Question

我遇到了这个问题。我有多个JComboBox（共5个）。

我为每个comboBox添加了一个ActionListener，但所有comboBox都使用相同的ActionListener

ComboBoxActionPerformed(java.awt.event.ActionEvent e)

当执行该操作时，我查看事件（e）并执行：

JComboBox c = ((JComboBox)e.getSource());
//DO WORK relating to c as thats the combobox that triggered.

但问题是，当我更改任何组合框中的内容时，Action总是由我附加actionlistner的最后一个组合框触发。

有人知道吗？

然后我切换到ItemListner。这就是我做的原因

class MyActionListner implements ItemListener 
{
    //STUFF
        @Override
        public void itemStateChanged(ItemEvent evt) 
        {
            //DO STUFF
    }
}
public JComboBox createCombo()
{
    JComboBox box = new JComboBox();
        box.setModel(new javax.swing.DefaultComboBoxModel(new String[] 
                { "val1", "val2","val3" }));
        RulesActionListner actionL = new RulesActionListner();
        box.addItemListener(actionL);
return box;
}

并多次调用createCombo但无论哪一个组合框项目在一侧被更改，我的ItemStateChanged方法从创建的最后一个组合框混合

createCombo是在运行时调用的，所以我有一个可变数量的组合框。

Answer 1

为每个调用添加单独的操作侦听器，而不是让一个操作侦听器运行if语句。这部分代码的逻辑很可能有一个错误，导致最后一个组合框被选中。（可能是应该是else if的else语句，等等）

将其分离将更加面向对象，并且从长远来看将更加灵活。

Answer 2

@user650608你的问题我不清楚，你的意思是——走这条路，还是我错了？，

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JFrame implements ActionListener, ItemListener {
    private static final long serialVersionUID = 1L;
    private JComboBox mainComboBox;
    private JComboBox subComboBox;
    private Hashtable<Object, Object> subItems = new Hashtable<Object, Object>();
    public ComboBoxTwo() {
        String[] items = {"Select Item", "Color", "Shape", "Fruit", "Size"};
        mainComboBox = new JComboBox(items);
        mainComboBox.addActionListener(this);
        mainComboBox.addItemListener(this);
        //prevent action events from being fired when the up/down arrow keys are used
        //mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
        getContentPane().add(mainComboBox, BorderLayout.WEST);
        subComboBox = new JComboBox();//  Create sub combo box with multiple models
        subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
        subComboBox.addItemListener(this);
        getContentPane().add(subComboBox, BorderLayout.CENTER);
        String[] subItems1 = {"Select Color", "Red", "Blue", "Green"};
        subItems.put(items[1], subItems1);
        String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"};
        subItems.put(items[2], subItems2);
        String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"};
        subItems.put(items[3], subItems3);
        String[] subItems4 = {"Select Size", "Big", "Middle", "Small"};
        subItems.put(items[4], subItems4);
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        String item = (String) mainComboBox.getSelectedItem();
        Object o = subItems.get(item);
        if (o == null) {
            subComboBox.setModel(new DefaultComboBoxModel());
        } else {
            subComboBox.setModel(new DefaultComboBoxModel((String[]) o));
        }
    }
    @Override
    public void itemStateChanged(ItemEvent e) {
        if (e.getStateChange() == ItemEvent.SELECTED) {
            if (e.getSource() == mainComboBox) {
                if (mainComboBox.getSelectedIndex() != 0) {
                    FirstDialog firstDialog = new FirstDialog(ComboBoxTwo.this,
                            mainComboBox.getSelectedItem().toString(), "Please wait,  Searching for ..... ");
                }
            } 
        }
    }
    private class FirstDialog extends JDialog {
        private static final long serialVersionUID = 1L;
        FirstDialog(final Frame parent, String winTitle, String msgString) {
            super(parent, winTitle);
            setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
            JLabel myLabel = new JLabel(msgString);
            JButton bNext = new JButton("Stop Processes");
            add(myLabel, BorderLayout.CENTER);
            add(bNext, BorderLayout.SOUTH);
            bNext.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent evt) {
                    setVisible(false);
                }
            });
            javax.swing.Timer t = new javax.swing.Timer(1000, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    setVisible(false);
                }
            });
            t.setRepeats(false);
            t.start();
            setLocationRelativeTo(parent);
            setSize(new Dimension(400, 100));
            setVisible(true);
        }
    }
    public static void main(String[] args) {
        JFrame frame = new ComboBoxTwo();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

Answer 3

您是否尝试使用ItemListener？

医生说，每次编辑组合框时都会触发ActionEvent。

谨致问候，Stéphane