我试图重置我的JTextField,以防输入空格。它把我抛了出来。
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Attempt to mutate in notification
我的代码是:
import java.awt.Color;
import java.awt.EventQueue;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
public class MainFrame extends JFrame {
private JPanel contentPane;
private JTextField textField;
/** * Launch the application. */
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
MainFrame frame = new MainFrame();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/** * Create the frame. */
public MainFrame() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JDesktopPane desktopPane = new JDesktopPane();
desktopPane.setBackground(Color.LIGHT_GRAY);
desktopPane.setBounds(6, 6, 438, 266);
contentPane.add(desktopPane);
textField = new JTextField();
textField.getDocument().addDocumentListener(new DocumentListener() {
public void changedUpdate(DocumentEvent e) {
}
public void removeUpdate(DocumentEvent e) {
}
public void insertUpdate(DocumentEvent e) {
if (textField.getText().contains(" ")) {
System.out
.println("Space was entered! clearing the text field");
textField.setText("");
}
}
});
textField.setBounds(133, 112, 134, 28);
desktopPane.add(textField);
textField.setColumns(10);
}
}
A DocumentListener
只适用于通知到底层的 Document
的 JTextComponent
. 你需要一个 DocumentFilter
此处
文档监听器不应该修改文档的内容;当监听器收到修改通知时,修改已经完成。取而代之的是,编写一个自定义文档,覆盖insertString或remove方法,或者两者都覆盖。详情请参见监听文档上的更改。
(从 http:/docs.oracle.comjavasetutorialuiswingeventsdocumentlistener.html。)
与其写一个自定义文档,我认为实现一个KeyListener更容易,如下图。
JTextField textField = new JTextField();
textField.addKeyListener( new KeyListener() {
@Override
public void keyTyped(KeyEvent arg0) {
if(arg0.getKeyChar() == ' '){
System.out.println("Space was entered! clearing the text field");
textField.setText("");
arg0.consume();
}
}
@Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void keyPressed(KeyEvent arg0) {
// TODO Auto-generated method stub
}
其中 arg0.consume()
防止清除文本字段后出现空格。