在Matlab的JSPlitPane中添加JscrollPane时，它没有收到mousewheelevent

Question

I've made a simple GUI in Swing with a big JPanel (displaying a big BufferedImage) inside a JScrollPane, inside a JSPlitPane, inside a JPanel, .... inside a JFrame.

When running/displaying my JFrame directly from Eclipse IDE, the JScrollPane receive correctly the mousewheel event and scroll when I scrolled my mouse wheel.

But when running from Matlab (I've build a JAR), the JScrollPane doesn't scroll when I've scroll the mouse wheel.

I've try to add manually mousewheellistener with some syso to debub/understand the problem, like this:

jscrollpane.addMouseWheelListener(new MouseWheelListener() {
    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        System.err.println("jscrollpane mouse wheel event");
    }
});

jsplitpane.addMouseWheelListener(new MouseWheelListener() {
    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        System.err.println("jsplitpane mouse wheel event");
    }
});

When running directly from Eclipse IDE, it's displayed "jscrollpane mouse wheel event" (this is OK). But when running my GUI from Matlab, it's displayed "jsplitpane mouse wheel event".

I've also add this piece of code to be sure that my jscrollpane has a mousewheellistener:

for (MouseWheelListener listener : jscrollpane.getMouseWheelListeners()) {
    System.err.println("ONE LISTENER FOR JSCROLLPANE");
}

And it's displayed two times (one time for my syso listener, and one time for the builtin mousewheellistener of the jscrollpane component).

So what happen in Matlab for the JScrollPane component? What can I do to force JscrollPane to receive MouseWheel events?

I think Matlab update the general awt mask events to prevent jscrollpane catching mousewheel event?

Answer 1

again (avoiding any mistake from typo) are

1. mousewheel by usung Matlab accesible,
2. mouse click to any JButton (in JPanel) selected JButton
3. if not then edit your question with Swing & Matlab in SSCCE form

.

import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;

public class JScrollBarUnitIncrement {

    private JFrame f = new JFrame("");
    private JPanel panel = new JPanel() {
        private static final long serialVersionUID = 1L;

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(80, 600);
        }
    };
    private JScrollPane sPane = new JScrollPane(panel) {
        private static final long serialVersionUID = 1L;

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(100, 200);
        }
    };
    private final int increment = 8;

    public JScrollBarUnitIncrement() {
        panel.setLayout(new GridLayout(40, 1));
        for (int i = 0; i != 40; i++) {
            JButton btn = new JButton("Button 2");
            panel.add(btn);
        }
        sPane.getVerticalScrollBar().setUnitIncrement(increment);
        KeyStroke kUp = KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0);
        KeyStroke kDown = KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0);
        sPane.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT).put(kUp, "actionWhenKeyUp");
        sPane.getActionMap().put("actionWhenKeyUp", new AbstractAction("keyUpAction") {
            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent e) {
                final JScrollBar bar = sPane.getVerticalScrollBar();
                int currentValue = bar.getValue();
                bar.setValue(currentValue - increment);
            }
        });
        sPane.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT).put(kDown, "actionWhenKeyDown");
        sPane.getActionMap().put("actionWhenKeyDown", new AbstractAction("keyDownAction") {
            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent e) {
                final JScrollBar bar = sPane.getVerticalScrollBar();
                int currentValue = bar.getValue();
                bar.setValue(currentValue + increment);
            }
        });
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(sPane);
        f.pack();
        f.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new JScrollBarUnitIncrement();
            }
        });
    }
}