This piece of code is a simplified version of a program I would convert to swing (using JTextField
and DocumentListener
). I have read some tutorials but I can't do it... I shouldn't use global variables and I have to use some like getSource()
( getDocument()
in this case?), because in the original program the number of JTextField is variable (they are generated inside a for
, so they haven't a "name"). This number depends on a value written in a text file.
import java.awt.*;
import java.awt.event.*;
class TestWindow extends Frame {
public TestWindow() {
Panel p = new Panel(new FlowLayout());
Label l = new Label("Temp");
TextField tf1 = new TextField();
TextField tf2 = new TextField();
tf1.addTextListener(new myTextListener(l));
tf2.addTextListener(new myTextListener(l));
p.add(tf1);
p.add(tf2);
tf1.setColumns(10);
tf2.setColumns(10);
p.add(l);
add(p);
pack();
setVisible(true);
}
class myTextListener implements TextListener {
Label input;
myTextListener(Label input) {
this.input = input;
}
public void textValueChanged(TextEvent e) {
input.setText(((TextField)(e.getSource())).getText());
}
}
}
public class Test {
public static void main(String[] args) {
new TestWindow();
}
}
This is a direct conversion of the code you posted to Swing that performs exactly the same task:
import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import java.awt.FlowLayout;
public class TestWindow extends JFrame {
public TestWindow() {
JPanel p = new JPanel(new FlowLayout());
JLabel l = new JLabel("Temp");
JTextField tf1 = new JTextField(10);
JTextField tf2 = new JTextField(10);
tf1.getDocument().addDocumentListener(new MyDocumentListener(l));
tf2.getDocument().addDocumentListener(new MyDocumentListener(l));
p.add(tf1);
p.add(tf2);
p.add(l);
add(p);
pack();
setVisible(true);
}
class MyDocumentListener implements DocumentListener{
private JLabel label;
MyDocumentListener(JLabel label) {
this.label = label;
}
@Override
public void insertUpdate(DocumentEvent e) {
handleTextChange(e);
}
@Override
public void removeUpdate(DocumentEvent e) {
handleTextChange(e);
}
@Override
public void changedUpdate(DocumentEvent e) {
handleTextChange(e);
}
private void handleTextChange(DocumentEvent e) {
try {
label.setText(e.getDocument().getText(0,e.getDocument().getLength()));
} catch (BadLocationException ignored) {
//todo: handle exception properly although this should never happen
}
}
}
public static void main(String[] args) {
new TestWindow();
}
}
Please note that DocumentListener provides more control for handling text change events than the TextListener, but I chose to handle them with one single method in order to exactly match your example's functionality
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