在文本字段的GUI中进行验证，并在验证后将文本字段设置为空

Question

我正在创建一个简单的GUI表单，其中有两个文本，一个是名称，另一个是电话号码，我试图验证它们，并在单击按钮时将它们设置为空。 但是，如果我再次不想单击JOptionPane Opened按钮，请为我提供这种方法。

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

public class Form {

    public static void main(String args[]) {
        final JFrame frame = new JFrame("Hello");
        final JButton btnOne = new JButton("save");
        final JTextField jname = new JTextField(8);
        final JTextField jphno = new JTextField(8);
        final JLabel lname = new JLabel("Name");
        final JLabel lphno = new JLabel("Phone no");
        frame.getContentPane().setBackground(new Color(58, 192, 126));

        GridBagLayout gbl = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();

        btnOne.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (jname.getText().length() <= 2) {
                    JOptionPane.showMessageDialog(null,
                            "please enter at    least Three digits");
                }
            }
        });
        btnOne.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (jphno.getText().trim().length() != 10) {
                    JOptionPane.showMessageDialog(null, 
                             "Please enter Valid Phone no");
                }
            }
        });
        btnOne.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                int j = jphno.getText().length();
                int h = jname.getText().length();
                if (e.getSource() == btnOne && j == 10 && h >= 3) {
                    jname.setText("");
                    jphno.setText("");
                }
            }
        });
        jname.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent fe) {
                if (fe.getSource() == jname) {
                    jname.setText("");
                }
            }
        });
        jphno.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent fe) {
                if (fe.getSource() == jphno) {
                    jphno.setText("");
                }
            }
        });
// adding components
        frame.setLayout(gbl);
        gbc.anchor = gbc.WEST;
        gbc.insets = new Insets(0, 30, 20, 30);
        gbc.gridx = 0;
        gbc.gridy = 0;
        frame.add(lname, gbc);
        gbc.gridx = 1;
        gbc.gridy = 0;
        frame.add(jname, gbc);
        gbc.gridx = 0;
        gbc.gridy = 1;
        frame.add(lphno, gbc);
        gbc.gridx = 1;
        gbc.gridy = 1;
        frame.add(jphno, gbc);
        gbc.gridx = 1;
        gbc.gridy = 2;
        frame.add(btnOne, gbc);
        btnOne.setBackground(Color.CYAN);
        btnOne.setBackground(Color.GRAY);
        frame.setVisible(true);
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
    }
}

Answer 1

您正在将多个动作侦听器添加到同一按钮。 结果，当按下按钮时，它们全部将触发。 在这种情况下，似乎首先触发了最后一个侦听器，这将重置数据，从而导致其他侦听器抱怨。

只需将您的代码合并到一个动作侦听器中即可。

或者，如mKorbel所建议，您可能希望调整方法并使用DocumentListener 即时验证JTextField的内容。

Answer 2

以下代码将为您工作-将所有三个动作侦听器组合为一个。

btnOne.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            //get length of the input fields
            int phoneInputLength = jphno.getText().length();
            int nameInputLength = jname.getText().length();

            //Check the name and phone number are the correct length first
            if (phoneInputLength != 10 && nameInputLength <= 2) {
                JOptionPane.showMessageDialog(null, "Please enter a name that is at least three characters" +
                                              "\nand enter a valid phone no (10 digits long)");
            } else if (phoneInputLength != 10) {
                JOptionPane.showMessageDialog(null, "Please enter Valid Phone no");
            } else if (nameInputLength <= 2) {
                JOptionPane.showMessageDialog(null,
                        "please enter at    least Three digits");
            } else {
                jname.setText("");
                jphno.setText("");
            }
        }
    });

另外，您不需要以下行：

 if (e.getSource() == btnOne)

通过行添加专门用于btnOne组件的动作侦听器时：

 btnOne.addActionListener

我还将做一些验证，以确保在输入框中输入的电话号码仅包含数字。 就像是

try {
    int number = Integer.parseInt(jphno.getText());
    //success - then you can make the text field empty 
} catch (NumberFormatException e1) {
     JOptionPane.showMessageDialog(null, "Phone numbers can only contain digits. " +
                                         "Please remove any characters that are not digits!",
                                         "Invalid Phone Number", JOptionPane.ERROR_MESSAGE);
}