java - JCombobox可编辑Java编程

Question

在我的可编辑组合框中。我想让用户在 JComboBox 中键入一个值的名称，如果所需的值不可用，它应该显示适当的错误消息。(如 JOptionPane)我需要在这里使用 getSelectedItem() 吗？

这是我的代码:

    import java.awt.FlowLayout;
    import java.awt.event.ItemEvent;
    import java.awt.event.ItemListener;

    import javax.swing.*;
    public class JTunes extends JFrame implements ItemListener{
    private JComboBox lyrics;
    private JTextField price;
    double sum = 0;
    public JTunes(){
        super("Lyrics");
        setSize(300,200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new FlowLayout());
        String[] lyrics1 = {"multiple", "data", "types", "used", "safely"};
        price = new JTextField(15);
         lyrics = new JComboBox(lyrics1);
         lyrics.setEditable(true);

         add(lyrics);
         add(price);
         lyrics.addItemListener(this);

    }

    public void itemStateChanged(ItemEvent e){
        String list = (String)lyrics.getSelectedItem();
            if(list.equals("multiple"))
                sum = 20;
            else if(list.equals("data"))
                sum = 30;
            else if(list.equals("types"))
                sum = 40;
            else if(list.equals("used"))
                sum = 50;
            else if(list.equals("safely"))
            sum = 60;


            price.setText(String.valueOf(sum));
    }
}

Answer 1

I want to allow the user to type the name of a value in the JComboBox and it should display an appropriate error message if the desired value is not available.

这毫无意义。使用组合框的要点是用户只能选择列表中存在的项目。

lyrics.setEditable(true);

去掉上面这行代码，用户将只能选择有效的项目。