Swing-使用另一帧中的jComboBox

Question

String variable = jComboMainMenu1.getSelectedItem().toString;

编辑：

**我得到的错误是combox对JFrame是私有的。没有办法改变，因为netbeans不允许我这样做？

表示//变量声明-不修改。

    new CustomerForm().setVisible(true);
    setVisible(false);

    String car = jComboBox1.getSelectedItem().toString();

}                                        


// Variables declaration - do not modify                                                 <-- can't be changed either.
private javax.swing.JButton jButton1;
private javax.swing.JComboBox jComboBox1;
private javax.swing.JComboBox jComboBox2;
private javax.swing.JComboBox jComboBox3;
private javax.swing.JComboBox jComboBox4;
private javax.swing.JComboBox jComboBox5;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JLabel jLabel6;
private javax.swing.JTextField jTextField1;
// End of variables declaration                   

Answer 1

编辑：调整到组合框

如果希望从客户表单中访问主表单的组合框,可以传递对该组合框的引用；例如在创建customer表单时。（将主窗体链接到客户窗体的另一种方法是将操作侦听器添加到主窗体中的组合框中，该组合框调用客户窗体中的一个方法，该方法获取作为参数传递的选定项。）

例如（使用Java8):

import java.awt.BorderLayout;
import javax.swing.*;

public class MainMenu {
    private CustomerForm customerForm;

    public static void main(String[] arguments) {
        SwingUtilities.invokeLater(() -> new MainMenu().createAndShowGui());
    }

    private void createAndShowGui() {
        JFrame frame = new JFrame("Stack Overflow");
        frame.setBounds(100, 100, 800, 600);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        JPanel panel = new JPanel(new BorderLayout());
        String[] comboBoxItems = {"one", "two", "three"};
        JComboBox<String> jComboBox1 = new JComboBox<>(comboBoxItems);
        panel.add(jComboBox1, BorderLayout.NORTH);
        JButton button = new JButton("Do it!");
        panel.add(button, BorderLayout.SOUTH);
        frame.getContentPane().add(panel);

        Database database = new Database();
        customerForm = new CustomerForm(database, jComboBox1);

        button.addActionListener(actionEvent -> customerForm.doSomething());

        frame.setVisible(true);
    }
}


class CustomerForm {
    private Database database;
    private JComboBox<String> comboBox;

    public CustomerForm(Database database, JComboBox<String> comboBox) {
        this.database = database;
        this.comboBox = comboBox;
    }

    public void doSomething() {
        System.out.println();
        System.out.println("CustomerForm.doSomething");
        System.out.println("database: " + database);

        System.out.println("comboBox.getSelectedItem().toString(): "
                           + comboBox.getSelectedItem().toString());
    }
}


class Database {
}