2020.10.7下拉列表框 JComboBox

import javax.swing.*;
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

class MyComboBox {
    private JFrame frame = new JFrame("Title");
    private Container cont = frame.getContentPane();
    private JComboBox jcb1 = null;
    private JComboBox jcb2 = null;
    private JPanel pan = new JPanel();
    public MyComboBox () {
        frame.setLayout(new GridLayout(2,1));
        String[] nations = {"中国","美国","英国","巴西","意大利"};
        Vector<String> v = new Vector<>();
        v.add("苹果");
        v.add("香蕉");
        v.add("葡萄");
        v.add("鸭梨");

        //实例化下拉列表框
        this.jcb1 = new JComboBox(nations);
        this.jcb2 = new JComboBox(v);

        //为下拉列表框增加一个边框
        this.jcb1.setBorder(BorderFactory.createTitledBorder("你最喜欢的国家?"));
        this.jcb2.setBorder(BorderFactory.createTitledBorder("你最喜欢的水果?"));

        cont.add(jcb1);
        cont.add(jcb2);

        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(1);
            }
        });
        frame.setSize(300,200);
        frame.setVisible(true);

    }
}
public class JComboBoxDemo01 {
    public static void main(String[] args) {
        new MyComboBox();
    }
}

与List一样，在JComboBox中也可以使用ComboBoxModel接口来构造JComboBox中的列表内容，ComboBoxModel接口是ListModel接口的子类，除了继承JListModel中的所有操作方法之外，还增加了如下的方法：

　　-void setSelectedItem(Object anItem)  设置选项内容

　　-Object getSelectedItem() 返回选择项