java - JComboBox 和 JButton 问题

Question

我的 JButtons 和 JComboBox 遇到问题，如果用户没有选择状态，我需要显示一条消息，然后他会收到警告，直到他选择状态。但它一直搞砸，当我选择一个状态时，它仍然告诉我选择一个状态。然后，对于 JButtons，用户应该选择一种性别，但他可以同时选择两种性别，我不确定为什么它应该只选择一种性别时这样做。

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.JTextField;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.LayoutStyle.ComponentPlacement;
import javax.swing.JComboBox;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JRadioButton;

private JPanel infoPanel = new JPanel();
private JTextField firstname;
private JTextField lastname;
private JTextField textArea;
private JLabel labelAge;
private JTextField age;
private JLabel lblState;
private JComboBox stateBox;
private JLabel labelSex;
private JRadioButton maleButton;
private JRadioButton femaleButton;

// creating the frame
public EnhancedWelcomeGUI() {

    // title
    super("Enhanced Welcome GUI");

    // Layout set up
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 506, 203);
    setContentPane(infoPanel);

    // Label to display Programmer Info
    JLabel programmerInfo = new JLabel(
            "Patrick McCully, CMIS 242, Homework 1");

    // Labeling for first name
    JLabel labelFirstName = new JLabel("First Name:");

    // text field for the first name
    firstname = new JTextField();
    firstname.setColumns(10);

    // labeling for the last name
    JLabel labelLastName = new JLabel("Last Name:");

    // text field for the last name
    lastname = new JTextField();
    lastname.setColumns(10);

    // labeling for the text field
    labelAge = new JLabel("Age:");

    // text field for the age
    age = new JTextField();
    age.setColumns(10);

    // the text field to display back to the user
    textArea = new JTextField();
    textArea.setEditable(false);

    lblState = new JLabel("State:");

    stateBox = new JComboBox();
    stateBox.setModel(new DefaultComboBoxModel(new String[] { "",
            "Alabama", "Alaska", "Arizona", "Arkansas", "California",
            "Colorado", "Connecticut", "Delaware", "Florida", "Georgia",
            "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas",
            "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts",
            "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana",
            "Nebraska", "Nevada", "New Hampshire", "New Jersey",
            "New Mexico", "New York", "North Carolina", "Ohio", "Oklahoma",
            "Oregon", "Pennsylvania", "Rhode Island", "South Carolina",
            "Tennessee", "Texas", "Utah", "Vermont", "Virginia",
            "Washington", "West Virginia", "Wisconsin", "Wyoming" }));

    labelSex = new JLabel("Sex:");
    maleButton = new JRadioButton("Male");
    femaleButton = new JRadioButton("Female");

    // the submit button when the user has entered the information
    JButton buttonWelcome = new JButton("Submit");

    //layout 
    GroupLayout groupLayoutPanel = new GroupLayout(infoPanel);

    groupLayoutPanel.setHorizontalGroup(
        groupLayoutPanel.createParallelGroup(Alignment.LEADING)
            .addGroup(groupLayoutPanel.createSequentialGroup()
                .addGap(10)
                .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                    .addComponent(programmerInfo, GroupLayout.PREFERRED_SIZE, 226, GroupLayout.PREFERRED_SIZE)
                    .addGroup(groupLayoutPanel.createSequentialGroup()
                        .addComponent(labelFirstName, GroupLayout.PREFERRED_SIZE, 66, GroupLayout.PREFERRED_SIZE)
                        .addGap(52)
                        .addComponent(labelLastName, GroupLayout.PREFERRED_SIZE, 66, GroupLayout.PREFERRED_SIZE)
                        .addGap(53)
                        .addComponent(labelAge, GroupLayout.PREFERRED_SIZE, 46, GroupLayout.PREFERRED_SIZE)
                        .addGap(71)
                        .addComponent(lblState, GroupLayout.PREFERRED_SIZE, 59, GroupLayout.PREFERRED_SIZE))
                    .addGroup(groupLayoutPanel.createSequentialGroup()
                        .addComponent(firstname, GroupLayout.PREFERRED_SIZE, 108, GroupLayout.PREFERRED_SIZE)
                        .addGap(10)
                        .addComponent(lastname, GroupLayout.PREFERRED_SIZE, 108, GroupLayout.PREFERRED_SIZE)
                        .addGap(10)
                        .addComponent(age, GroupLayout.PREFERRED_SIZE, 108, GroupLayout.PREFERRED_SIZE)
                        .addGap(10)
                        .addComponent(stateBox, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
                    .addGroup(groupLayoutPanel.createSequentialGroup()
                        .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                            .addComponent(labelSex, GroupLayout.PREFERRED_SIZE, 35, GroupLayout.PREFERRED_SIZE)
                            .addGroup(groupLayoutPanel.createSequentialGroup()
                                .addGap(28)
                                .addComponent(maleButton))
                            .addGroup(groupLayoutPanel.createSequentialGroup()
                                .addGap(77)
                                .addComponent(femaleButton)))
                        .addPreferredGap(ComponentPlacement.RELATED)
                        .addComponent(buttonWelcome, GroupLayout.PREFERRED_SIZE, 135, GroupLayout.PREFERRED_SIZE))
                    .addComponent(textArea, GroupLayout.PREFERRED_SIZE, 471, GroupLayout.PREFERRED_SIZE)))
    );
    groupLayoutPanel.setVerticalGroup(
        groupLayoutPanel.createParallelGroup(Alignment.LEADING)
            .addGroup(groupLayoutPanel.createSequentialGroup()
                .addGap(11)
                .addComponent(programmerInfo)
                .addGap(10)
                .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                    .addComponent(labelFirstName)
                    .addComponent(labelLastName)
                    .addComponent(labelAge)
                    .addComponent(lblState))
                .addGap(11)
                .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                    .addComponent(firstname, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addComponent(lastname, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addComponent(age, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addComponent(stateBox, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
                .addGap(10)
                .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                    .addComponent(maleButton)
                    .addGroup(groupLayoutPanel.createSequentialGroup()
                        .addGroup(groupLayoutPanel.createParallelGroup(Alignment.LEADING)
                            .addGroup(groupLayoutPanel.createSequentialGroup()
                                .addGap(4)
                                .addComponent(labelSex))
                            .addGroup(groupLayoutPanel.createParallelGroup(Alignment.BASELINE)
                                .addComponent(femaleButton)
                                .addComponent(buttonWelcome)))
                        .addGap(6)
                        .addComponent(textArea, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)))
                .addGap(26))
    );
    infoPanel.setLayout(groupLayoutPanel);

    buttonWelcome.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent pressing) {

            int userAge;

            // a try/catch to catch any error and display
            // back to the user that he must finish
            try {

                String first = firstname.getText();
                String last = lastname.getText();
                Object state = stateBox.getSelectedItem();
                userAge = Integer.parseInt(age.getText());
                boolean male = maleButton.isSelected();
                boolean female = femaleButton.isSelected();

                // warning section
                if (userAge <= 0) {

                    JOptionPane.showMessageDialog(null,
                            "Must be a positive age");

                } else if (!state.equals(state)) {

                    JOptionPane.showMessageDialog(null,
                            "Must select state");

                }                   

                if (male) {

                    textArea.setText("Welcome Male " + first + ", " + last
                            + " of " + userAge + " years old from " + state);

                } else if (female) {

                    textArea.setText("Welcome Female " + first + ", "
                            + last + " of " + userAge + " years old from "
                            + state);

                }

                // display back the error as a pop up
            } catch (Exception e) {

                JOptionPane.showMessageDialog(null,
                        "Must Complete your Info");

            }

        }
    });

}

// to execute the program
public static void main(String[] args) {

    EnhancedWelcomeGUI frame = new EnhancedWelcomeGUI();
    frame.setVisible(true);

}
}

Answer 1

为了更友好的组合框，不要存储和清空状态。相反，使用自定义渲染器来显示“选择状态”等消息。

然后您可以通过确保 JComboBox 的 getSelectedIndex() 方法不为 -1 来简单测试是否已选择状态。

查看Combo Box Prompt用于为您执行此操作的自定义渲染器。