[英]Workaround for adding ActionListener to JTextArea
我有一個程序在一個JTextArea中獲取帶有文件路徑的輸入字符串,然后將其內容加載到第二個JTextArea。 問題是當使用JTextArea時,我無法添加一個actionListener,它將在離開此字段時在第二個JTextArea中加載內容。 如何解決這個問題?
protected JTextArea inputField, outputField;
public Main(){
super(new BorderLayout());
inputField = new JTextArea(5, 20);
outputField = new JTextArea(2, 20);
//inputField.addActionListener(this);
inputField.setEditable(false);
JScrollPane scroller2 = new JScrollPane(inputField);
JScrollPane scroller1 = new JScrollPane(outputField);
this.add(scroller1, BorderLayout.WEST);
this.add(scroller2, BorderLayout.EAST);
}
public void actionPerformed(ActionEvent evt) {
String text = inputField.getText();
(loading contents of file)
}
你不想要一個actionListener,你想要一個FocusListener 。
JTextArea text = ...;
text.addFocusListener(new FocusListener() {
public void focusGained(FocusEvent e) {}
public void focusLost(FocusEvent e) {
// Load your content.
}
});
或者,為了充實我的第一個評論,試試這個使用JButton的SSCCE(和內容的JEditorPane)。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import java.io.File;
class LoadDocument {
public static void main(String[] args) {
Runnable r = new Runnable() {
public void run() {
final JFrame f = new JFrame();
f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
JPanel contentPane = new JPanel( new BorderLayout(3,3) );
contentPane.setBorder( new EmptyBorder(5,5,5,5) );
// has convenience methods to load documents..
final JEditorPane content = new JEditorPane();
JScrollPane sp = new JScrollPane(content);
sp.setPreferredSize( new Dimension(400,400) );
contentPane.add( sp, BorderLayout.CENTER );
final JFileChooser jfc = new JFileChooser();
JButton open = new JButton("Open File");
open.addActionListener( new ActionListener(){
public void actionPerformed(ActionEvent ae) {
int result = jfc.showOpenDialog(f);
if (result==JFileChooser.APPROVE_OPTION) {
File file = jfc.getSelectedFile();
try {
content.setPage( file.toURI().toURL() );
} catch(Exception e) {
e.printStackTrace();
JOptionPane.showMessageDialog(
f,
"File load error!",
e.getMessage(),
JOptionPane.ERROR_MESSAGE
);
}
}
}
} );
JToolBar tb = new JToolBar();
tb.add(open);
contentPane.add( tb, BorderLayout.NORTH );
f.setContentPane( contentPane );
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}
如果只需要ActionListener,請檢查以下示例:
textArea.addFocusListener(new FocusAdapter() {
@Override
public void focusLost(FocusEvent e) {
actionListener.actionPerformed(new ActionEvent(e.getSource(), e.getID(), "focusLost"));
}
});
它等於:
textArea.addActionListener(actionListener);
PS actionListener必須是final或class字段才能以這種方式使用。
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