This ad hoc approach leverages the existing JScrollPane
actions that are usually used in key bindings. You’ll have to tune N
to your implementation of Scrollable
.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.Timer;
/** @see http://stackoverflow.com/questions/7201509 */
public class ScrollAction extends JPanel {
private static final int TILE = 64;
private static final int DELTA = 16;
public ScrollAction() {
this.setOpaque(false);
this.setFocusable(true);
this.setPreferredSize(new Dimension(50 * TILE, 50 * TILE));
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.lightGray);
int w = this.getWidth() / TILE + 1;
int h = this.getHeight() / TILE + 1;
for (int row = 0; row < h; row++) {
for (int col = 0; col < w; col++) {
if ((row + col) % 2 == 0) {
g.fillRect(col * TILE, row * TILE, TILE, TILE);
}
}
}
}
private void display() {
JFrame f = new JFrame("ScrollAction");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JScrollPane scrollPane = new JScrollPane(this);
final ScrollTimer left = new ScrollTimer(scrollPane, "scrollLeft");
final ScrollTimer right = new ScrollTimer(scrollPane, "scrollRight");
final ScrollTimer up = new ScrollTimer(scrollPane, "scrollUp");
final ScrollTimer down = new ScrollTimer(scrollPane, "scrollDown");
final JViewport viewPort = scrollPane.getViewport();
viewPort.setPreferredSize(new Dimension(5 * TILE, 5 * TILE));
viewPort.addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
left.stop();
if (e.getX() < DELTA) {
left.start();
}
right.stop();
if (e.getX() > viewPort.getWidth() - DELTA) {
right.start();
}
up.stop();
if (e.getY() < DELTA) {
up.start();
}
down.stop();
if (e.getY() > viewPort.getHeight() - DELTA) {
down.start();
}
}
});
f.add(scrollPane);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private static final class ScrollTimer implements ActionListener {
private static int N = 10;
private static int DELAY = 100;
private String cmd;
private Timer timer;
private Action action;
private JScrollPane scrollPane;
private int count;
public ScrollTimer(JScrollPane scrollPane, String action) {
this.cmd = action;
this.timer = new Timer(DELAY, this);
this.action = scrollPane.getActionMap().get(action);
this.scrollPane = scrollPane;
}
@Override
public void actionPerformed(ActionEvent e) {
if (count++ < N) {
action.actionPerformed(new ActionEvent(scrollPane, 0, cmd));
} else {
timer.stop();
}
}
public void start() {
count = 0;
timer.start();
}
public void stop() {
timer.stop();
count = 0;
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new ScrollAction().display();
}
});
}
}