java - 文本字段事件、规则等

Question

我对 JTextField 有一些疑问。

1. 哪个事件取代了 NetBeans 中 JTextField 的 TextChanged 事件？
2. 当文本字段中的值发生更改时，我希望将其总和添加到 Total Fee 中。同样，我正在使用此代码，但它不起作用。

代码:

private void TutionFeesKeyTyped(java.awt.event.KeyEvent evt) {
   TotalFee.setText(""+Integer.parseInt(TutionFees.getText())+
     Integer.parseInt(LibraryFees.getText())+Integer.parseInt(UDFees.getText())+
     Integer.parseInt(USFees.getText())+Integer.parseInt(OtherFees.getText())+
     Integer.parseInt(SecurityFees.getText())) ;   
     // TODO add your handling code here:
}

基本上我正在使用:

Integer.parseInt()

将文本转换为数字数据，以便我可以添加它们..

我正在使用 KeyTyped 事件，但它不允许在文本字段中输入任何内容。

Answer 1

切勿将 KeyListener 用于此类事情，因为它可能会扰乱 JTextField 的基本功能。要在输入时监听 JTextField 内容的更改，请考虑将 DocumentListener 添加到 JTextField 的文档中。

如果您需要将输入限制为数字或使用任何其他类型的限制，请通过 DocumentFilter 设置文档的过滤器(请记住首先将其转换为 PlainDocument)，或使用 JFormattedTextField ，或使用(我最喜欢的)JSpinner。

例如，

Document doc = myTextField.getDocument();
doc.addDocumentListener(new DocumentListener() {

        void insertUpdate(DocumentEvent e) {
            // ... code to check document change here
        }

        void removeUpdate(DocumentEvent e){
            // ... code to check document change here
        }

        void changedUpdate(DocumentEvent e){
            // ... code to check document change here
        }

});

<小时/>

例如，同时使用 DocumentListener 和 DocumentFilter，第一个用于添加数字，第二个确保仅输入数字。

现在编辑以处理 15 个 JTextField:

import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;
import javax.swing.text.PlainDocument;

@SuppressWarnings("serial")
public class DocListenerEg extends JPanel {
   private static final int FIELD_COUNT = 15;
   private static final int COLS = 6;
   private List<JTextField> fieldList = new ArrayList<>();
   private JTextField sumField = new JTextField(COLS);

   public DocListenerEg() {
      sumField.setFocusable(false);

      DocListener docListener = new DocListener();
      DocFilter docFilter = new DocFilter();
      for (int i = 0; i < FIELD_COUNT; i++) {
         JTextField textField = new JTextField(COLS);
         Document doc = textField.getDocument();
         doc.addDocumentListener(docListener);
         ((PlainDocument) doc).setDocumentFilter(docFilter);
         add(textField);
         fieldList.add(textField);
         String labelText = i < (FIELD_COUNT - 1) ? "+" : "=";
         add(new JLabel(labelText));
      }
      add(sumField);
   }

   private class DocFilter extends DocumentFilter {
      private boolean checkIfIntegerOrEmpty(String text) {
         if (text.isEmpty()) {
            return true;
         } else {
            try {
               Integer.parseInt(text);
               return true;
            } catch (NumberFormatException e) {
            }
         }
         return false;
      }

      @Override
      public void insertString(FilterBypass fb, int offset, String string,
            AttributeSet attr) throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         sb.insert(offset, string);

         if (checkIfIntegerOrEmpty(sb.toString())) {
            super.insertString(fb, offset, string, attr);
         }

      }

      @Override
      public void remove(FilterBypass fb, int offset, int length)
            throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         int end = offset + length;
         sb.replace(offset, end, "");

         if (checkIfIntegerOrEmpty(sb.toString())) {            
            super.remove(fb, offset, length);
         }
      }

      @Override
      public void replace(FilterBypass fb, int offset, int length, String text,
            AttributeSet attrs) throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         int end = offset + length;
         sb.replace(offset, end, text);

         if (checkIfIntegerOrEmpty(sb.toString())) {            
            super.replace(fb, offset, length, text, attrs);
         }
      }
   }

   private class DocListener implements DocumentListener {

      private void textChanged() {
         int sum = 0;
         for (JTextField jTextField : fieldList) {
            String text = jTextField.getText().trim();
            if (!text.isEmpty()) {
               sum += Integer.parseInt(text);
            }
         }
         sumField.setText(String.valueOf(sum));
      }

      @Override
      public void insertUpdate(DocumentEvent e) {
         textChanged();
      }

      @Override
      public void removeUpdate(DocumentEvent e) {
         textChanged();
      }

      @Override
      public void changedUpdate(DocumentEvent e) {
         textChanged();
      }

   }

   private static void createAndShowGui() {
      DocListenerEg mainPanel = new DocListenerEg();

      JFrame frame = new JFrame("DocListenerEg");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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

<小时/>

编辑:您在评论中指出，

Read whole code, much informative , however way too big if i want to implement for more then 30 textfields .. I have solved the problem , now pasting the solution.

好的，下面的新代码添加了 100 个 JTextFields 中的数字，同样对原始代码进行了最小的更改。要查看哪种解决方案效果最好，哪种解决方案扩展性最好，请尝试更改当前的解决方案以处理类似的问题:

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.util.ArrayList;
import java.util.List;

import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;
import javax.swing.text.PlainDocument;

@SuppressWarnings("serial")
public class DocListenerEg extends JPanel {
   private static final int COLS = 6;
   private static final int GAP = 5;
   private static final int SIDE = 10;
   private List<JTextField> fieldList = new ArrayList<>();
   private JTextField sumField = new JTextField(COLS);

   public DocListenerEg() {
      sumField.setFocusable(false);

      JPanel additionFieldPanel = new JPanel(new GridLayout(SIDE, SIDE, GAP, GAP));
      additionFieldPanel.setBorder(BorderFactory.createTitledBorder("Numbers To Add"));

      DocListener docListener = new DocListener();
      DocFilter docFilter = new DocFilter();
      for (int i = 0; i < SIDE * SIDE; i++) {
         JTextField textField = new JTextField(COLS);
         Document doc = textField.getDocument();
         doc.addDocumentListener(docListener);
         ((PlainDocument) doc).setDocumentFilter(docFilter);
         fieldList.add(textField);
         additionFieldPanel.add(textField);
      }

      JPanel sumPanel = new JPanel();
      sumPanel.add(new JLabel("Sum Of All Numbers:"));
      sumPanel.add(sumField);

      setLayout(new BorderLayout());
      add(additionFieldPanel, BorderLayout.CENTER);
      add(sumPanel, BorderLayout.PAGE_END);
   }

   private class DocFilter extends DocumentFilter {
      private boolean checkIfIntegerOrEmpty(String text) {
         if (text.isEmpty()) {
            return true;
         } else {
            try {
               Integer.parseInt(text);
               return true;
            } catch (NumberFormatException e) {
            }
         }
         return false;
      }

      @Override
      public void insertString(FilterBypass fb, int offset, String string,
            AttributeSet attr) throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         sb.insert(offset, string);

         if (checkIfIntegerOrEmpty(sb.toString())) {
            super.insertString(fb, offset, string, attr);
         }

      }

      @Override
      public void remove(FilterBypass fb, int offset, int length)
            throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         int end = offset + length;
         sb.replace(offset, end, "");

         if (checkIfIntegerOrEmpty(sb.toString())) {            
            super.remove(fb, offset, length);
         }
      }

      @Override
      public void replace(FilterBypass fb, int offset, int length, String text,
            AttributeSet attrs) throws BadLocationException {
         Document doc = fb.getDocument();
         String preText = doc.getText(0, doc.getLength());

         StringBuilder sb = new StringBuilder(preText);
         int end = offset + length;
         sb.replace(offset, end, text);

         if (checkIfIntegerOrEmpty(sb.toString())) {            
            super.replace(fb, offset, length, text, attrs);
         }
      }
   }

   private class DocListener implements DocumentListener {

      private void textChanged() {
         int sum = 0;
         for (JTextField jTextField : fieldList) {
            String text = jTextField.getText().trim();
            if (!text.isEmpty()) {
               System.out.println(text);
               sum += Integer.parseInt(text);
            }
         }
         sumField.setText(String.valueOf(sum));
      }

      @Override
      public void insertUpdate(DocumentEvent e) {
         textChanged();
      }

      @Override
      public void removeUpdate(DocumentEvent e) {
         textChanged();
      }

      @Override
      public void changedUpdate(DocumentEvent e) {
         textChanged();
      }

   }

   private static void createAndShowGui() {
      DocListenerEg mainPanel = new DocListenerEg();

      JFrame frame = new JFrame("DocListenerEg");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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