java - 在列表 gui 中循环

Question

大家好，我对第一个 RadioButton 中 JList 中的循环有疑问，它是正确的，但在第二个示例中，如果我尝试执行另一个星号，则循环将出错，这是迄今为止我的代码。

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

public class LOOPING extends JFrame implements ItemListener
{
    JFrame jeframe = new JFrame("LOOPING");
    JPanel jenel = new JPanel();
    JLabel let = new JLabel("Choose a letter");
    JRadioButton first = new JRadioButton("A");
    JRadioButton second = new JRadioButton("B");
    JRadioButton third = new JRadioButton("C");
    JRadioButton fourth = new JRadioButton("D");
    JList asterisk = new JList();
    JLabel je = new JLabel();

    DefaultListModel aslist = new DefaultListModel();

    public LOOPING()
    {
        jenel.setLayout(null);
        jeframe.setVisible(true);
        jeframe.setBounds(330,100,200,370);
        jeframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        let.setBounds(10,10,100,20);
        first.setBounds(20,50,50,30);
        second.setBounds(20,110,50,30);
        third.setBounds(100,50,50,30);
        fourth.setBounds(100,110,50,30);
        asterisk.setBounds(07,150,170,170);
        je.setBounds(07,90,110,170);

        jenel.add(let);
        jenel.add(first);
        jenel.add(second);
        jenel.add(third);
        jenel.add(fourth);
        jenel.add(asterisk);
        jenel.add(je);

        first.addItemListener(this);
        second.addItemListener(this);
        third.addItemListener(this);
        fourth.addItemListener(this);
        getContentPane().add(jenel);
        jeframe.add(jenel);
    }
    public void itemStateChanged(ItemEvent e)
    {
        ItemSelectable beu;
        beu = e.getItemSelectable();
        String s = "*";

        if(beu == first)
        {
            for(int a=0; a<=4; a++)
            {
                for(int b=1; b<a; b++)
                System.out.print(" ");

                je.setText(je.getText() + s);
                aslist.addElement(je.getText());
                asterisk.setModel(aslist);
            }

        }
        if(beu == second)
        {
            for(int v=1; v<=5; v++)
                    {
            for(int j=v; j<=5; j++)
                je.setText(s);
                System.out.println();
                                aslist.addElement(je.getText());
                                asterisk.setModel(aslist);
                    }

        }
        String boo = "*";
        if(beu == third)

        {
            for(int u=5; u>0; u--)
            {
                for(int i=u; i>0; i--)
                {
                je.setText(je.getText() + boo);
                System.out.print(" ");
                }

                aslist.addElement(je.getText());
                asterisk.setModel(aslist);
            }


        }
    }
    public static void main(String [] args)
    {
        LOOPING lup = new LOOPING();
    }
}

Answer 1

为你的beu == second尝试一下这个。您需要连接 *。您目前仅使用 one *

设置文本

    if (beu == second) {
        for (int v = 1; v <= 5; v++) {
            String stars = "";
            for (int j = v; j <= 5; j++) {
                stars += s;
            }
            je.setText(stars);
            System.out.println();
            aslist.addElement(je.getText());
            asterisk.setModel(aslist);
        }
    }

输出

*****
****
***
**
*

为此

    *
   **
  ***
 ****
*****

您需要两个循环，一个用于空格，另一个用于星号。试试这个

  if (beu == third) {
        for (int m = 0; m < 6; m++) {
            String stars = "";
            for (int k = 6; k >= m; k--) {
                System.out.print(" ");
                stars += " ";
            }
            for (int i = 1; i <= m; i++) {
                System.out.print("*");
                stars += "*";

            }
            je.setText(stars);
            aslist.addElement(je.getText());
            asterisk.setModel(aslist);

            System.out.println();
        }
    }