Use Action
"to separate functionality and state from a component." In the example below, the actions change the index
and update()
a JLabel
from a List<String>
. Your application might update a JTextArea
from a List<Employee>
.
package gui;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
/**
* @see http://stackoverflow.com/a/20116944/230513
*/
public class PrevNext {
private final List<String> list = new ArrayList<>(
Arrays.asList("Alpher", "Bethe", "Gamow", "Dirac", "Einstein"));
private int index = list.indexOf("Einstein");
private final JLabel label = new JLabel(list.get(index), JLabel.CENTER);
private void display() {
JFrame f = new JFrame("PrevNext");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new JButton(new AbstractAction("<Prev") {
@Override
public void actionPerformed(ActionEvent e) {
if (--index < 0) {
index = list.size() - 1;
}
update();
}
}), BorderLayout.LINE_START);
f.add(label);
f.add(new JButton(new AbstractAction("Next>") {
@Override
public void actionPerformed(ActionEvent e) {
if (++index == list.size()) {
index = 0;
}
update();
}
}), BorderLayout.LINE_END);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private void update() {
label.setText(list.get(index));
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new PrevNext().display();
}
});
}
}
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