java - 我 setEnabled(false) 后复选框没有被禁用

Question

如果有 30 个复选框，而我不希望选中超过 6 个复选框。我有一个 int 来跟踪检查了多少个。每个盒子都有一个项目监听器，它调用一个方法来查看该 int 的值，如果它达到 6，该方法会在每个盒子上调用 setEnabled(false)。 然而，即使在 int number_of_boxes_checked 达到 6 之后，这些框也不会被禁用。

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JCheckBox;
import java.awt.GridLayout;
import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import javax.swing.JLabel;

public class JLottery2 extends JFrame {

private JPanel contentPane;
int number_of_boxes_checked = 1;
JCheckBox[] checkBox = new JCheckBox[30];
JLabel label = new JLabel("0");

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                JLottery2 frame = new JLottery2();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the frame.
 */
public JLottery2() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 586, 360);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    JPanel panel = new JPanel();
    panel.setBounds(10, 11, 321, 299);
    contentPane.add(panel);
    panel.setLayout(new GridLayout(5, 6, 0, 0));

    JPanel panel_1 = new JPanel();
    panel_1.setBounds(330, 11, 230, 299);
    contentPane.add(panel_1);

    panel_1.add(label);

    for (int i = 0; i < 30; ++i) {
        checkBox[i] = new JCheckBox(Integer.toString(i + 1));
        panel.add(checkBox[i]);
    }
    for (int i = 0; i < 30; ++i) {
        checkBox[i].addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent e) {
                limit_checkBoxes();
            }
        });
    }
}

public void limit_checkBoxes() {
    label.setText(Integer.toString(number_of_boxes_checked));
    if (number_of_boxes_checked > 6) {
        for (int i = 0; i > 30; ++i) {
            checkBox[i].setEnabled(false);
        }
    } else {
        ++number_of_boxes_checked;

    }
}
}

Answer 1

在您的 limit_checkBoxes() 中方法，你想要i < 30 ，不是i > 30在循环。请参阅我嵌入的评论。

    label.setText(Integer.toString(number_of_boxes_checked));
    if (number_of_boxes_checked > 6) {
        for (int i = 0; i < 30; ++i) { //<- your bug was here, I fixed it
            checkBox[i].setEnabled(false);
        }
    } else {
        ++number_of_boxes_checked;
   }