java 即使未选中复选框，JCheckbox isSelected() 也会返回 true

JCheckbox isSelected() returns true even if the checkbox is not checked

提问by Benoit Goderre

I am having trouble with JCheckboxes, although I have used them often before.

我在使用JCheckboxes时遇到了麻烦，尽管我以前经常使用它们。

Basically, I create a very simple window with check boxes, then check if they are selected. When doing that check, it displays the JCheckboxas selected, even if it is not. Here is my code. To reproduce my issue, run the project, then click Start. Even if the createStatisticsFilesCheckBoxis set as not selected, from the constructor, checking if it is selected in the ActionListenermethod returns true. Thanks in advance!

基本上，我创建了一个非常简单的带有复选框的窗口，然后检查它们是否被选中。进行该检查时，它会显示JCheckbox为已选择，即使不是。这是我的代码。要重现我的问题，请运行该项目，然后单击“开始”。即使createStatisticsFilesCheckBox被设置为未选择，从构造函数中，检查它是否在ActionListener方法中被选择返回true。提前致谢！

package Queries;

包查询；

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Test extends Thread implements ActionListener 
{
    private JButton cancelButton, backButton, startButton;
    private JCheckBox createQueriesCheckBox,createStatisticsFilesCheckBox, createPokerHandIDFilesCheckBox;
    private JFrame frame;

    public void actionPerformed(ActionEvent e)
    {
        if ("Start".equals(e.getActionCommand()))
        {
            if (createQueriesCheckBox.isSelected() == true);
            {
                // Code here
            }

            if (createStatisticsFilesCheckBox.isSelected() == true);
            {
                // Code here
                // Always show as selected
                System.out.println("Test");
            }

            if (createPokerHandIDFilesCheckBox.isSelected() == true);
            {
                // Code here
            }

            start();
        }
        else if ("Back".equals(e.getActionCommand()))
        {
            // Code here
        }
        else if ("Cancel".equals(e.getActionCommand()))
        {
            System.exit(0);
        }
    }

    public Test()
    {       
        JPanel mainPanel = new JPanel(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();

        gbc.insets = new Insets(4, 4, 4, 4);
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridheight = 1;
        gbc.gridwidth = 1;

        mainPanel.add(checkBoxesPanel(), gbc);

        gbc.gridy++;

        mainPanel.add(buttonsPanel(), gbc);

        frame = new JFrame("Actions");

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(mainPanel);
        frame.setVisible(true);
        frame.pack();
    }

    /**
     * Panel that contains the Cancel and Continue buttons
     * 
     * @return panel
     */
    public JPanel buttonsPanel()
    {
        JPanel buttonsPanel = new JPanel(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();

        gbc.insets = new Insets(10, 10, 10, 10);
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridheight = 1;
        gbc.gridwidth = 1;
        gbc.anchor = GridBagConstraints.EAST;

        cancelButton = new JButton("Cancel");
        cancelButton.addActionListener(this);

        buttonsPanel.add(cancelButton, gbc);

        backButton = new JButton("Back");
        backButton.addActionListener(this);

        gbc.gridx++;

        buttonsPanel.add(backButton, gbc);

        startButton = new JButton("Start");
        startButton.addActionListener(this);

        gbc.gridx++;

        buttonsPanel.add(startButton, gbc);

        return buttonsPanel;
    }

    /**
     * Panel that contains the check boxes for the types of queries
     * 
     * @return panel
     */
    public JPanel checkBoxesPanel()
    {
        JPanel checkBoxesPanel = new JPanel(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();

        gbc.insets = new Insets(4, 4, 4, 4);        

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridheight = 1;
        gbc.gridwidth = 1;
        gbc.anchor = GridBagConstraints.WEST;       

        createQueriesCheckBox = new JCheckBox("Create queries", true);

        checkBoxesPanel.add(createQueriesCheckBox, gbc);

        createStatisticsFilesCheckBox = new JCheckBox("Create statistics files", false);

        gbc.gridy++;
        checkBoxesPanel.add(createStatisticsFilesCheckBox, gbc);

        createPokerHandIDFilesCheckBox = new JCheckBox("Create PokerHandID files", false);

        gbc.gridy++;
        checkBoxesPanel.add(createPokerHandIDFilesCheckBox, gbc);

        return checkBoxesPanel;
    }

    public static void main(String[] args)
    {
        new Test();
    }

    public void run()
    {       
        System.exit(0);
    }

}

回答by camickr

if (createStatisticsFilesCheckBox.isSelected() == true);

You have a trailing ";" on all your if statements which ends the if statement.

你有一个尾随的“;” 在所有结束 if 语句的 if 语句上。

Therefore every statement after the if statement is executed unconditionally.

因此，if 语句之后的每个语句都无条件地执行。

Get rid of the ";".

去掉“;”。

回答by Shady Watson

The Code is working fine it returns false if checkbox is not selected try copy pasting it when i copied yours it had 3 closing brackets missing, Let me know if it is working for you.

代码工作正常，如果未选中复选框，则返回 false 尝试复制粘贴它，当我复制您的代码时，它缺少 3 个右括号，让我知道它是否适合您。

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Test extends Thread implements ActionListener {
   private JButton cancelButton, backButton, startButton;
   private JCheckBox createQueriesCheckBox,createStatisticsFilesCheckBox,  createPokerHandIDFilesCheckBox;
   private JFrame frame;

    public void actionPerformed(ActionEvent e){
        if ("Start".equals(e.getActionCommand())){
            if (createQueriesCheckBox.isSelected() == true){
        // Code here
            }

            if (createStatisticsFilesCheckBox.isSelected() == true){
        // Code here
        // Always show as selected
                System.out.println("Test");
            }

            if (createPokerHandIDFilesCheckBox.isSelected() == true){
        // Code here
            }

            start();
        }
        else if ("Back".equals(e.getActionCommand())){
    // Code here
        }
        else if ("Cancel".equals(e.getActionCommand())){
            System.exit(0);
        }
    }           

public Test(){       
    JPanel mainPanel = new JPanel(new GridBagLayout());

    GridBagConstraints gbc = new GridBagConstraints();

    gbc.insets = new Insets(4, 4, 4, 4);
    gbc.gridx = 0;
    gbc.gridy = 0;
    gbc.gridheight = 1;
    gbc.gridwidth = 1;

    mainPanel.add(checkBoxesPanel(), gbc);

    gbc.gridy++;

    mainPanel.add(buttonsPanel(), gbc);

    frame = new JFrame("Actions");

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setContentPane(mainPanel);
    frame.setVisible(true);
    frame.pack();
       }public JPanel buttonsPanel(){
    JPanel buttonsPanel = new JPanel(new GridBagLayout());

    GridBagConstraints gbc = new GridBagConstraints();

    gbc.insets = new Insets(10, 10, 10, 10);
    gbc.gridx = 0;
    gbc.gridy = 0;
    gbc.gridheight = 1;
    gbc.gridwidth = 1;
    gbc.anchor = GridBagConstraints.EAST;

    cancelButton = new JButton("Cancel");
    cancelButton.addActionListener(this);

    buttonsPanel.add(cancelButton, gbc);

    backButton = new JButton("Back");
    backButton.addActionListener(this);

    gbc.gridx++;

    buttonsPanel.add(backButton, gbc);

    startButton = new JButton("Start");
    startButton.addActionListener(this);

    gbc.gridx++;

    buttonsPanel.add(startButton, gbc);

    return buttonsPanel;
}

public JPanel checkBoxesPanel(){
    JPanel checkBoxesPanel = new JPanel(new GridBagLayout());

    GridBagConstraints gbc = new GridBagConstraints();

    gbc.insets = new Insets(4, 4, 4, 4);        

    gbc.gridx = 0;
    gbc.gridy = 0;
    gbc.gridheight = 1;
    gbc.gridwidth = 1;
    gbc.anchor = GridBagConstraints.WEST;       

    createQueriesCheckBox = new JCheckBox("Create queries", true);

    checkBoxesPanel.add(createQueriesCheckBox, gbc);

    createStatisticsFilesCheckBox = new JCheckBox("Create statistics files", false);

    gbc.gridy++;
    checkBoxesPanel.add(createStatisticsFilesCheckBox, gbc);

    createPokerHandIDFilesCheckBox = new JCheckBox("Create PokerHandID files", false);

    gbc.gridy++;
    checkBoxesPanel.add(createPokerHandIDFilesCheckBox, gbc);

    return checkBoxesPanel;
}

public static void main(String[] args){
    new Test();
}

public void run(){       
    System.exit(0);

}
}