从另一个类调用时，Java PropertyChangeListener 不工作

Question

我有一个 PanouAddContoriMetro 类

jtfSeria.addPropertyChangeListener(new PropertyChangeListener() {

  public void propertyChange(PropertyChangeEvent evt) {
               // do something
        }
}

从 PanouAddContoriMetro 类调用时工作:jtfSeria.setText("Test");

但是当我从另一个更改属性时不工作

类 (PanouExpAutorizatii) : pacm.jtfSeria.setText("Test");

Answer 1

我认为这里的问题是您认为 PropertyChangeListener 会监听 setText() - 它不会。在 propertyChange 的文档中它指出的方法:

This method gets called when a bound property is changed.

此外在 setText方法的文档:

Note that text is not a bound property, so no PropertyChangeEvent is fired when it changes. To listen for changes to the text, use DocumentListener.

---

所以，这是一个使用 DocumentListener 的例子.日志中显示为灰色的所有内容均由 PropertyChangeListener 触发，所有显示为黑色的内容均由 DocumentListener 触发:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTextPane;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.Style;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;

public class Example {

    private JTextPane log;
    private int counter;

    public Example() {
        log = new JTextPane();
        log.setEditable(false);

        JTextField field = new JTextField(15);
        field.addPropertyChangeListener(new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                appendMessage(evt.getPropertyName(), Color.GRAY);
            }
        });
        field.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void changedUpdate(DocumentEvent e) {
                appendMessage("Changed", Color.BLACK);
            }

            @Override
            public void insertUpdate(DocumentEvent e) {
                appendMessage("Inserted", Color.BLACK);
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                appendMessage("Removed", Color.BLACK);
            }
        });
        field.setText("Test");

        JFrame frame = new JFrame();
        frame.add(field, BorderLayout.NORTH);
        frame.add(new JScrollPane(log));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private void appendMessage(String message, Color color) {
        StyledDocument doc = log.getStyledDocument();
        Style style = log.addStyle("style1", null);
        StyleConstants.setForeground(style, color);
        try {
            doc.insertString(doc.getLength(), ++counter + ". " + message + "\n", style);
        } catch (BadLocationException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Example();
            }
        });
    }

}