Question

我的代码如下所示：

private void populateRoleNameComboBox() {
    roleNameJComboBox.removeAllItems();
    roleNameJComboBox.addItem(UserAccountDirectory.ADMIN_ROLE);
    roleNameJComboBox.addItem(UserAccountDirectory.SALESPERSON_ROLE);
    roleNameJComboBox.addItem(UserAccountDirectory.SUPPLIER_ROLE);   
    roleNameJComboBox.addItem(UserAccountDirectory.CUSTOMER_ROLE);
   //populatePersonNameComboBox();
}


private void populatePersonNameComboBox() {
        personNameJComboBox.removeAllItems();

       if(roleNameJComboBox.getSelectedItem().equals(UserAccountDirectory.SUPPLIER_ROLE)){
        for(Supplier s : supplierDirectory.getSupplierList()){
            personNameJComboBox.addItem(s);
                    }
               }
        else if(roleNameJComboBox.getSelectedItem().equals(UserAccountDirectory.SALESPERSON_ROLE)){
            for(Person p : employeeDirectory.getSalesPersonList()){
                personNameJComboBox.addItem(p);
                    }
               }
            else if(roleNameJComboBox.getSelectedItem().equals(UserAccountDirectory.CUSTOMER_ROLE)){
            for(Person person : customerDirectory.getCustomerList()){
                personNameJComboBox.addItem(person);
                    }
              }
  }

我的personNameJComboBox没有显示任何值。如何实现逻辑以获取第二个comboBox的值基于第一个。

Answer 1

这是一个简单的示例来帮助您入门。基本上，只要第一个组合框的选定项发生更改，您就需要更改第二个组合框的模型。

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class ComboBoxTwo extends JFrame implements ActionListener
{
    private JComboBox mainComboBox;
    private JComboBox subComboBox;
    private Hashtable subItems = new Hashtable();

    public ComboBoxTwo()
    {
        String[] items = { "Select Item", "Color", "Shape", "Fruit" };
        mainComboBox = new JComboBox( items );
        mainComboBox.addActionListener( 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 );

        //  Create sub combo box with multiple models

        subComboBox = new JComboBox();
        subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
        getContentPane().add( subComboBox, BorderLayout.EAST );

        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);
//      mainComboBox.setSelectedIndex(1);
    }

    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 ) );
        }
    }

    public static void main(String[] args)
    {
        JFrame frame = new ComboBoxTwo();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible( true );
     }
}

Answer 2

默认情况下，每个JComboBox与DefaultComboBoxModel关联，以添加项目或管理项目的状态更改。但是，如果您要向JComboBox添加/删除项目，则必须使用MutableComboboxModel和DefaultComboBoxModel实施MutableComboBoxModel的实施方式。

我认为你的personNameJComboBox.addItem(item)无法正常工作，除非你试图填充数据而没有听取roleNameJComboBox的动作事件，至少在项目将被选中。确保您使用ActionListener roleNameJcomboBox并实施actionPerformed()功能，您应该在其中调用populatePersonNameComboBox()功能。

如何获得comboBox值？

2 个答案: