即使失去焦点，如何将分配的光标保留给 JDialog？

Question

Is there a way to retain the set mouse cursor even the JDialog is not in focus?

I have the following SSCCE:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Test extends JDialog {
  public Test() {
    super((Frame) null, true);

    setLayout(new BorderLayout());
    setModalityType(Dialog.ModalityType.MODELESS);
    setType(Window.Type.UTILITY);
    setUndecorated(true);
    setAlwaysOnTop(true);
    setBackground(Color.BLACK);
    setSize(300, 300);
    setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
    setCursor(Cursor.getPredefinedCursor(Cursor.N_RESIZE_CURSOR));
    getContentPane().setBackground(Color.BLACK);
    getContentPane().setCursor(Cursor.getPredefinedCursor(Cursor.N_RESIZE_CURSOR));
    setLocationRelativeTo(null);
    var label = new JLabel("Focused");
    label.setForeground(Color.WHITE);
    addWindowFocusListener(new WindowAdapter() {
      @Override
      public void windowGainedFocus(WindowEvent e) {
        label.setText("Focused");
      }

      @Override
      public void windowLostFocus(WindowEvent e) {
        label.setText("Not Focused");
      }
    });

    add(label, BorderLayout.CENTER);
  }

  public static void main(String[] args) {

    // Create the GUI on the event-dispatching thread
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        Test sw = new Test();

        // Display the window.
        sw.setVisible(true);
      }
    });
  }
}

Here is what is happening:

My goal is for the resize cursor to be retained on mouse hover even if the JDialog is not focused.

Tried on AdoptOpenJDK 11 & 15 and Liberica JDK 11 on MacOS Catalina 10.15.4

Answer 1

Add a mouse listener for your dialog. By using the MouseAdapter implementation, you can override only the methods that you want.

addMouseListener(new MouseAdapter() {
    @Override
    public void mouseEntered(MouseEvent e) {
        super.mouseEntered(e);
        setCursor(Cursor.getPredefinedCursor(Cursor.N_RESIZE_CURSOR));
    }
    
    @Override
    public void mouseExited(MouseEvent e) {
        super.mouseExited(e);
        setCursor(Cursor.getDefaultCursor());
    }
});