java - 使用 swing、JButtons 等在程序上显示信息时出现问题

Question

我正在使用 swing 制作一个乘法表。它基本上由 JButton 组成。该表是根据用户的输入形成的。用户通过输入数字来选择表格的大小。我需要做的最后一件事是创建一个标题，显示创建的表的编号。这是我的示例代码，如果您运行它，您会看到它针对垂直数字完成了。我怎样才能得到上面的数字并正确格式化以代表每一列。谢谢。

package lab7;

import java.awt.BorderLayout;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class GUIMultiplicationTable{
JFrame theFrame;
int number = 0;
JPanel panel, answerPanel, topPanel, leftPanel;
JLabel answerLabel, topLabel, leftLabel;

private void createAndShowGui(){
    String x;
    do{
        x = JOptionPane.showInputDialog(null, "Enter the number");
        number = Integer.parseInt(x);
    }while (number <= 0);
    theFrame = new JFrame("Multiplication Table");
    panel = new JPanel(new GridLayout(number, number));

    answerPanel = new JPanel();     
    answerLabel = new JLabel();

    topPanel = new JPanel();
    topLabel = new JLabel();

    leftPanel = new JPanel();
    leftLabel = new JLabel();


    for (int i = 0; i < number; i++){
        JLabel blah = new JLabel(Integer.toString(i + 1));
        panel.add(blah);//add center to label
        for (int j = 0; j < number; j++){

            JButton button = new JButton();
            if (i == 0){

                button.setText(String.valueOf(j + 1));
            }
            if (j == 0){
                button.setText(String.valueOf(i + 1));
            }
            for (int k = 1; k < number; k++)
            {
                if (i == k)
                {
                    button.setText(String.valueOf((j + 1) * (k + 1)));
                }
            }
            button.addActionListener(new ButtonsTableActionListener(i, j));
            panel.add(button);
        }   
    }

    answerPanel.add(answerLabel);
    theFrame.add(answerPanel, BorderLayout.SOUTH);

    topPanel.add(topLabel);
    theFrame.add(topPanel, BorderLayout.NORTH);

    theFrame.add(panel);
    theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    theFrame.pack();
    theFrame.setLocationRelativeTo(null);
    theFrame.setVisible(true);
}
public static void main(String[] args){
    SwingUtilities.invokeLater(new Runnable(){
        public void run(){
            GUIMultiplicationTable h = new GUIMultiplicationTable();
            h.createAndShowGui();
        }
    });
}

private class ButtonsTableActionListener implements ActionListener{
    private int theRow, theColumn;

    public ButtonsTableActionListener(int row, int column){
        theRow = row;
        theColumn = column;
    }

    @Override
    public void actionPerformed(ActionEvent e){
        int value = (theRow + 1) * (theColumn + 1);
        answerLabel.setText("The value is: " + value + ".\nI got that by multiplying \n" +    (theRow + 1) + "x" + (theColumn + 1));
    }
};
}

Answer 1

实现此目的的一个简单方法是将按钮的位置存储在 ActionListener 中，您可以通过创建自己的类扩展 ActionListener 来实现此目的，而不是这样做一个匿名类。这样，按钮执行的代码就已经拥有完成您想要的任何操作所需的信息。

而且你也不需要按钮数组，只需在面板中一次添加一个按钮，同时添加actionListener。

这是您已清理并正常工作的代码。现在，您可以做任何您想做的事情，而不是显示对话框。

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class GUIMultiplicationTable
{
    JFrame theFrame;
    int number = 0;
    JPanel panel;

    private void createAndShowGui()
    {
        String x;
        do
        {
            x = JOptionPane.showInputDialog(null, "Enter the number");
            number = Integer.parseInt(x);
        } while (number <= 0);
        theFrame = new JFrame("Multiplication Table");
        panel = new JPanel(new GridLayout(number, number));
        for (int i = 0; i < number; i++)
        {
            for (int j = 0; j < number; j++)
            {
                JButton button = new JButton();
                if (i == 0)
                {
                    button.setText(String.valueOf(j + 1));
                }
                if (j == 0)
                {
                    button.setText(String.valueOf(i + 1));
                }
                for (int k = 1; k < number; k++)
                {
                    if (i == k)
                    {
                        button.setText(String.valueOf((j + 1) * (k + 1)));
                    }
                }
                button.addActionListener(new ButtonsTableActionListener(i, j));
                panel.add(button);
            }
        }
        theFrame.add(panel);
        theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        theFrame.pack();
        theFrame.setLocationRelativeTo(null);
        theFrame.setVisible(true);

    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
            public void run()
            {
                GUIMultiplicationTable h = new GUIMultiplicationTable();
                h.createAndShowGui();
            }
        });

    }

    private class ButtonsTableActionListener implements ActionListener
    {
        private int _row, _column;

        public ButtonsTableActionListener(int row, int column)
        {
            _row = row;
            _column = column;
        }

        @Override
        public void actionPerformed(ActionEvent e)
        {
            // /do something
            int value = (_row + 1) * (_column + 1);
            String message = "I'm the button in the position (" + _row + ", " + _column + ")\nMy value is " + value + " = " + (_row + 1) + "*" + (_column + 1);
            JOptionPane.showMessageDialog(theFrame, message);
        }
    };
}