使用 LostFocus 事件在 Java 中验证文本字段

Question

我正在使用 LostFocus 事件验证两个文本字段，如下所示：

textRegNo.addFocusListener(new FocusListener() {            
        @Override
        public void focusLost(FocusEvent arg0) {
            // TODO Auto-generated method stub
            regNo1=textRegNo.getText();
            Pattern pattern1 = Pattern.compile("^[A-Z]{2}[ -][0-9]{1,2}(?: [A-Z])?(?: [A-Z]*)? [0-9]{4}$");
            Matcher matcher1 = pattern1.matcher(regNo1);

            if (!matcher1.find()){
                JOptionPane.showMessageDialog(null, "Invalid Vehicle No!!!\n Vehicle no should be of the form MH 03 KS 2131!!");
            }                           
        }
        @Override
        public void focusGained(FocusEvent arg0) {
            // TODO Auto-generated method stub

        };
    }); 


textMobNo.addFocusListener(new FocusListener() {            
        @Override
        public void focusLost(FocusEvent arg0) {
            // TODO Auto-generated method stub
            mobNo1=textMobNo.getText();
            Pattern pattern2 = Pattern.compile("^[789]\\d{9}$");
            Matcher matcher2 = pattern2.matcher(mobNo1);

            System.out.println("'"+mobNo1+"'");
            if (!matcher2.find()){
                JOptionPane.showMessageDialog(null, "Phone no must be a 10 digit number!!");
            }                           
        }

        @Override
        public void focusGained(FocusEvent arg0) {
            // TODO Auto-generated method stub

        };
    });

我的问题是，当我失去对第一个文本字段的关注并将焦点移动到第二个文本字段时，两个字段都会打印错误消息（两个 lostfocus 事件下的 IF 块内的 MESSAGE。） 当我在第一个文本字段中输入错误并将焦点移动到第二个字段时，它应该只打印第一个文本字段的错误消息。但两者的打印错误。

第一个文本字段是 textRegNo 第二个文本字段是 textMobNo

Answer 1

问题的症状围绕着这个过程。

1. textMobNo 获得关注...
2. 导致textRegNo失去焦点...
3. textRegNo 已验证并发现无效，textRegNo 现在显示错误消息...
4. 焦点转移到对话框并...
5. textMobNo 失去焦点（因为对话框获得焦点）

如果可以的话，您应该避免使用焦点来验证字段，而是使用InputVerifier

简单示例

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.swing.InputVerifier;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.JTextComponent;

public class TestInputVerifier {

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

    public TestInputVerifier() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            JTextField field = new JTextField(20);
            field.setInputVerifier(new RegExpInputVerifier("^[A-Z]{2}[ -][0-9]{1,2}(?: [A-Z])?(?: [A-Z]*)? [0-9]{4}$"));
            add(field, gbc);

            field = new JTextField(20);
            field.setInputVerifier(new RegExpInputVerifier("^[789]\\d{9}$"));
            add(field, gbc);
        }

    }

    public class RegExpInputVerifier extends InputVerifier {

        private String expression;

        public RegExpInputVerifier(String expression) {
            this.expression = expression;
        }

        public String getExpression() {
            return expression;
        }

        @Override
        public boolean verify(JComponent input) {
            boolean verified = false;
            if (input instanceof JTextComponent) {
                JTextComponent field = (JTextComponent) input;
                String regNo1 = field.getText();
                Pattern pattern1 = Pattern.compile(expression);
                Matcher matcher1 = pattern1.matcher(regNo1);
            }
            return verified;
        }
    }
}