import java.awt.*;

import javax.swing.*;

import javax.swing.border.*;

import java.awt.event.*;

public class Test extends JFrame {

    private JPanel jPane;//大的面板

    private JTextField textField;//文本框

    public JComboBox comboBox;//下拉选择框

    public static String a =null;

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {

            public void run() {

                try {

                	Test frame = new Test();

                    frame.setVisible(true);

//             	设置窗口可见

                } catch (Exception e) {

                    e.printStackTrace();

                }

            }

        });

    }

    /**

     * Create the frame.

     */

    public Test() {

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//      EXIT_ON_CLOSE相当于执行System.exit(0);的动作方法退出应用程序，关闭进程

//      如果不写这句话点击X我们也能关闭窗口，但是在后台进程里面我们会发现我们的进程数并不减少

        setBounds(200, 200, 400, 400);//首次点开，发现距离屏幕左边,上方200，长宽均为400

        jPane = new JPanel();

        jPane.setBorder(new EmptyBorder(5, 5, 5, 5));

        setContentPane(jPane);

        jPane.setLayout(null);

//按照规定的位置显示，否则按照默认的FlowLayout（每个JPanel对象初始化时都使用FlowLayout布局，）布局显示的

        comboBox = new JComboBox();

        String[] select = {"选项一","选项二","选项三"};

//        添加选项值

        comboBox.setModel(new DefaultComboBoxModel(select));

        comboBox.setBounds(15, 15, 100, 25);

        jPane.add(comboBox);

        textField = new JTextField();

        textField.setBounds(150, 15, 76, 22);

        jPane.add(textField);

        textField.setText("选项一");

        comboBox.addItemListener(new ItemListener() {

            @Override

            public void itemStateChanged(ItemEvent e) {

                if(e.getStateChange() == ItemEvent.SELECTED) {

                	 textField.setText(comboBox.getSelectedItem().toString());

                	 a = textField.getText();

                	 System.out.print(a);

                }

            }

        });

    }

}