Why Doesn\'t My Java Wait Cursor Appear Over Custom Cursors?

Problem with Java Wait Cursor Display

Issue:

When displaying a wait cursor in a Java application, the cursor does not appear if the mouse is over a panel that defines its own cursor. This issue is demonstrated in the provided Sample Self-Contained Executable (SSCE).

Cause:

The default implementation of Java's wait cursor only affects the cursor directly set on the component. Panels with custom cursors take precedence, overriding the wait cursor.

Solution:

To remedy this, the wait cursor should be set on the glasspane of the JFrame that contains the component seeking to display it.

Implementation:

1. Create an action listener that:

   • Schedules a task to set the wait cursor after a specified delay.
   • Executes the original action listener after the delay.

2. When the action listener is triggered:

   • Set the wait cursor on the JFrame's glasspane.
   • Add a mouse adapter to the glasspane to prevent mouse events from reaching underlying components.
   • Make the glasspane visible.

3. When the timer task completes:

   • Restore the original cursor to the JFrame.
   • Remove the mouse adapter from the glasspane.
   • Hide the glasspane.

Modified SSCE:

The modified SSCE incorporates these changes to ensure the wait cursor is displayed even when panels have custom cursors:

public class BusyCursorTest extends javax.swing.JFrame {

    private javax.swing.JPanel cursorPanel = null;

    // ... (remaining code)

    public static void main(String[] args) {
        new BusyCursorTest();
    }

    public static java.awt.event.ActionListener getActionListener(final javax.swing.JFrame frame,
        final java.awt.event.ActionListener originalActionListener) {

        java.awt.event.ActionListener actionListener = new java.awt.event.ActionListener() {

            public void actionPerformed(final java.awt.event.ActionEvent e) {

                java.util.TimerTask timerTask = new java.util.TimerTask() {

                    public void run() {
                        originalCursor = frame.getCursor();
                        startWaitCursor(frame);
                    }

                };
                java.util.Timer timer = new java.util.Timer();

                try {
                    timer.schedule(timerTask, DELAY_MS);
                    originalActionListener.actionPerformed(e);
                } finally {
                    timer.cancel();
                    stopWaitCursor(frame);
                }
            }

        };
        return actionListener;
    }

    private static void startWaitCursor(javax.swing.JFrame frame) {
        frame.getGlassPane().setCursor(java.awt.Cursor.getPredefinedCursor(java.awt.Cursor.WAIT_CURSOR));
        frame.getGlassPane().addMouseListener(mouseAdapter);
        frame.getGlassPane().setVisible(true);
    }

    private static void stopWaitCursor(javax.swing.JFrame frame) {
        frame.getGlassPane().setCursor(originalCursor);
        frame.getGlassPane().removeMouseListener(mouseAdapter);
        frame.getGlassPane().setVisible(false);
    }

    // ... (remaining code)
}

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