邏輯錯誤或重新油漆/重新驗證Java JFrame

Question

我要嘗試做的是，當我輸入詳細信息時，它將在按下按鈕時驗證textFiled是否為空，如果為空，則將顯示一條消息，說明。 然后它將移至下一個類似於許多基於Web的注冊表的textFile，我試圖找出的是為什么消息不會更改？

將此代碼粘貼到ecilpse文件中並運行它應該顯示簡單的框架以及我要執行的操作。

當名字字段為空時，該消息顯示在框架的底部，有人可以解釋為什么當名字字段包含文本而中間名不包含文本時為什么不顯示下一條消息？

大多數邏輯位於代碼的底部。

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.Color;
import javax.swing.UIManager;
import javax.swing.JPanel;
import com.jgoodies.forms.layout.FormLayout;
import com.jgoodies.forms.layout.ColumnSpec;
import com.jgoodies.forms.layout.RowSpec;
import com.jgoodies.forms.factories.FormFactory;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.Font;
import javax.swing.SwingConstants;
import javax.swing.JRadioButton;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import javax.swing.JButton;
import javax.swing.JComboBox;

public class start {

private JFrame frame;
private JTextField tfFirstname;
private JTextField tfMiddlenames;
private JTextField tfSurname;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                start window = new start();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public start() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frame = new JFrame();

    frame.setBounds(100, 100, 505, 429);

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    frame.getContentPane().setLayout(null);

    final JPanel panelClientNew = new JPanel();
    panelClientNew.setBackground(new Color(0, 102, 255));
    panelClientNew.setBounds(10, 11, 469, 299);
    frame.getContentPane().add(panelClientNew);
    panelClientNew.setLayout(null);

    JLabel lblFirstname = new JLabel("Firstname :");
    lblFirstname.setHorizontalAlignment(SwingConstants.RIGHT);
    lblFirstname.setVerticalAlignment(SwingConstants.BOTTOM);
    lblFirstname.setForeground(new Color(255, 255, 255));
    lblFirstname.setFont(new Font("Tahoma", Font.BOLD, 13));
    lblFirstname.setBounds(10, 16, 163, 14);
    panelClientNew.add(lblFirstname);

    tfFirstname = new JTextField();
    tfFirstname.setFont(new Font("Tahoma", Font.PLAIN, 13));
    tfFirstname.setBounds(177, 10, 282, 27);
    panelClientNew.add(tfFirstname);
    tfFirstname.setColumns(10);

    JLabel lblMiddlenames = new JLabel("Middlenames :");
    lblMiddlenames.setHorizontalAlignment(SwingConstants.RIGHT);
    lblMiddlenames.setForeground(new Color(255, 255, 255));
    lblMiddlenames.setFont(new Font("Tahoma", Font.BOLD, 13));
    lblMiddlenames.setBounds(10, 47, 163, 14);
    panelClientNew.add(lblMiddlenames);

    tfMiddlenames = new JTextField();
    tfMiddlenames.setFont(new Font("Tahoma", Font.PLAIN, 13));
    tfMiddlenames.setBounds(177, 41, 282, 27);
    panelClientNew.add(tfMiddlenames);
    tfMiddlenames.setColumns(10);

    JLabel lblSurname = new JLabel("Surname :");
    lblSurname.setHorizontalAlignment(SwingConstants.RIGHT);
    lblSurname.setForeground(new Color(255, 255, 255));
    lblSurname.setFont(new Font("Tahoma", Font.BOLD, 13));
    lblSurname.setBounds(10, 78, 163, 14);
    panelClientNew.add(lblSurname);

    tfSurname = new JTextField();
    tfSurname.setFont(new Font("Tahoma", Font.PLAIN, 13));
    tfSurname.setBounds(177, 72, 282, 27);
    panelClientNew.add(tfSurname);
    tfSurname.setColumns(10);



    JButton btnAdd = new JButton("Add");
    btnAdd.addMouseListener(new MouseAdapter() {
        @Override
        public void mousePressed(MouseEvent arg0) {
            /*
             * 
             * 
             *
             *I am trying to create a message that validates on certain circumstances
             * 
             * 
             * 
             */

            if(tfFirstname.getText().equals(null) || tfFirstname.getText().equals("") || tfFirstname.getText().equals(false)) {
                JPanel panelMessage = new JPanel();
                panelMessage.setBackground(new Color(30, 144, 255));
                panelMessage.setBounds(10, 321, 469, 29);
                frame.getContentPane().add(panelMessage);

                JLabel lblPersonSaved = new JLabel("Please Enter Firstname :");
                lblPersonSaved.setForeground(new Color(255, 255, 255));
                lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
                panelMessage.add(lblPersonSaved);
                frame.revalidate();
                panelMessage.revalidate();
                frame.repaint();

            }
            else if (tfMiddlenames.getText().equals(null) || tfMiddlenames.getText().equals("") || tfMiddlenames.getText().equals(false)) {
                JPanel panelMessage = new JPanel();
                panelMessage.setBackground(new Color(30, 144, 255));
                panelMessage.setBounds(10, 321, 469, 29);
                frame.getContentPane().add(panelMessage);

                JLabel lblPersonSaved = new JLabel("Please Enter Middlenames :");
                lblPersonSaved.setForeground(new Color(255, 255, 255));
                lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
                panelMessage.add(lblPersonSaved);

                frame.revalidate();
                panelMessage.revalidate();
                frame.repaint();

            }
            else if (tfSurname.getText().equals(null) || tfSurname.getText().equals("") || tfSurname.getText().equals(false)) {
                JPanel panelMessage = new JPanel();
                panelMessage.setBackground(new Color(30, 144, 255));
                panelMessage.setBounds(10, 321, 469, 29);
                frame.getContentPane().add(panelMessage);

                JLabel lblPersonSaved = new JLabel("Please Enter Surname :");
                lblPersonSaved.setForeground(new Color(255, 255, 255));
                lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
                panelMessage.add(lblPersonSaved);
                frame.revalidate();
                panelMessage.revalidate();
                frame.repaint();

            }
            else {


                //Validation has passed

            }
        }
    });
    btnAdd.setBounds(370, 265, 89, 23);
    panelClientNew.add(btnAdd);





}
}

Answer 1

我建議您使用InputVerifier，因為在允許您離開JTextField之前，這將驗證JTextField的內容正確（您希望定義的任何方式）。 現在，它不會阻止您按下其他JButton，而是按下其他按鈕，因此，如果您具有提交按鈕，則需要采取其他預防措施。 下面顯示了一個簡單的InputVerifier的示例，該示例檢查JTextField是否為空：

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

@SuppressWarnings("serial")
public class InputVerifierExample extends JPanel {
   public static final Color WARNING_COLOR = Color.red;
   private JTextField firstNameField = new JTextField(10);
   private JTextField middleNameField = new JTextField(10);
   private JTextField lastNameField = new JTextField(10);
   private JTextField[] nameFields = { 
         firstNameField, 
         middleNameField,
         lastNameField };
   private JLabel warningLabel = new JLabel("  ");

   public InputVerifierExample() {
      warningLabel.setOpaque(true);

      JPanel namePanel = new JPanel();
      namePanel.add(new JLabel("Name:"));
      MyInputVerifier verifier = new MyInputVerifier();
      for (JTextField field : nameFields) {
         field.setInputVerifier(verifier);
         namePanel.add(field);
      }
      namePanel.add(new JButton(new SubmitBtnAction()));

      setLayout(new BorderLayout());
      add(namePanel, BorderLayout.CENTER);
      add(warningLabel, BorderLayout.SOUTH);
   }

   private class SubmitBtnAction extends AbstractAction {
      public SubmitBtnAction() {
         super("Submit");
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         // first check all fields aren't empty
         for (JTextField field : nameFields) {
            if (field.getText().trim().isEmpty()) {
               return;  // return if empty
            }
         }
         String name = "";
         for (JTextField field : nameFields) {
            name += field.getText() + " ";
            field.setText("");
         }
         name = name.trim();
         JOptionPane.showMessageDialog(InputVerifierExample.this, name, "Name Entered",
               JOptionPane.INFORMATION_MESSAGE);
      }
   }

   private class MyInputVerifier extends InputVerifier {

      @Override
      public boolean verify(JComponent input) {
         JTextField field = (JTextField) input;
         if (field.getText().trim().isEmpty()) {
            warningLabel.setText("Please do not leave this field empty");
            warningLabel.setBackground(WARNING_COLOR);
            return false;
         }
         warningLabel.setText("");
         warningLabel.setBackground(null);
         return true;
      }

   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("InputVerifier Example");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new InputVerifierExample());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Answer 2

1. 看一下DocumentListener ，

2. 在start_up上僅啟用第一個JTextField ，如果在第一個JTextField中鍵入了任何（取決於您）字符，然后啟用第二個JTextField，依此類推...，

3. 如果要過濾，更改或替換來自鍵盤的輸出，請使用DocumentFilter

4. 在JTextFields包含不正確的長度的情況下， 例如將背景更改為Color.red （來自DocumentListeners events ），例如

5. 同意HFOE關於LayoutManagers