Listener that has events for when a frame is snapped to the left or right of screen

Question

I know WindowStateListener will tell me if a component is maximized vertically, horizontally, or both. At least, it says it will. I do not know how to maximize a window exclusively horizontally or exclusively vertically outside of snapping the window to the left edge or right edge of my screen. Is there another listener for this behavior? Or will I need to make something myself that tracks mouse location in relation to the screen? I made an example program that displays what I've described.

SSCCE

import java.awt.Dimension;
import java.awt.event.WindowEvent;
import java.awt.event.WindowStateListener;
import javax.swing.JFrame;
public class Main {
public static void main(String[] args) {
    SnapFrame frame = new SnapFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(new Dimension(500,500));
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);

    }
}
class SnapFrame extends JFrame implements WindowStateListener{
    public SnapFrame(){
        super();
        addWindowStateListener(this);
    }


@Override
public void windowStateChanged(WindowEvent arg0) {
     //will print a statement for all state change events except snapping to left/right edges of screen
    System.out.println("state changed");
}
}

If I wanted to have things triggered by this behavior, and there are no other listeners that have events for this, would a decent idea be to get my screen size and watch my mouse location for when it comes near the edge of my screen?

Answer 1

This source detects when the frame is snapped to the top or bottom of screen, using a ComponentListener. I don't know how to configure my Windows to snap to the left or right.

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

public class Main {

    public static void main(String[] args) {
        SnapFrame frame = new SnapFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(500, 500));
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
}

class SnapFrame extends JFrame implements ComponentListener {

    Dimension screenSize;

    public SnapFrame() {
        super();
        screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        addComponentListener(this);
    }

    @Override
    public void componentResized(ComponentEvent e) {
        Rectangle r = getBounds();

        if (r.getMinY()==0  || r.getMaxY()==(int)screenSize.getHeight()) {
            System.out.print("Well snap!");
        }
    }

    @Override
    public void componentMoved(ComponentEvent ignore) {}

    @Override
    public void componentShown(ComponentEvent ignore) {}

    @Override
    public void componentHidden(ComponentEvent ignore) {}
}

Other tips

• Don't extend frame or other top level containers. Instead create & use an instance of one.
• Swing GUIs should be created and updated on the EDT. See Concurrency in Swing for more details.