使用LostFocus事件在Java中进行文本字段验证 [英] Textfield Validation in Java using LostFocus event

问题描述

我正在使用LostFocus事件验证两个文本字段，如下所示:

I am validating two textfields using LostFocus event as follows:

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至第二个文本字段时，两个字段都将显示错误消息(两个lostfocus事件下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到第二个字段时，它应该仅输出第一个文本字段的错误消息.但是两者的打印错误.

My problem is that when i lose focus on 1st textfield and move that focus to the 2nd text filed error message gets printed for both the fields(MESSAGE inside IF block under both lostfocus event.) When i give wrong input into 1st textfield and move focus to 2nd field it should only print the error message for 1st text field. But its printing error for both.

第一个文本字段是textRegNo 第二个文本字段是textMobNo

1st textfield is textRegNo 2nd textfield is textMobNo

推荐答案

问题的症状与该过程有关.

The symptom of the problem revolves around this process.

1. textMobNo获得关注...
2. 这会导致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(因为对话框获得了焦点)

1. textMobNo gains focus...
2. which causes textRegNo to lose focus...
3. textRegNo is validated and found to be invalid, textRegNo now displays an error message...
4. Focus is transferred to the dialog and...
5. textMobNo loses focus (because the dialog gained focus)

如果可以的话，应避免使用焦点作为验证字段的方法，而应使用 InputVerifier

You should avoid using focus as a means to validate fields if you can and instead use an 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;
        }
    }
}

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