Screen edge snapping : Frame « Swing JFC « Java

Screen edge snapping

import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;

public class WindowSnapper extends ComponentAdapter {

  private boolean locked = false;

  private int sd = 50;

  public void componentMoved(ComponentEvent evt) {
    if (locked)
    Dimension size = Toolkit.getDefaultToolkit().getScreenSize();
    int nx = evt.getComponent().getX();
    int ny = evt.getComponent().getY();
    // top
    if (ny < 0 + sd) {
      ny = 0;
    // left
    if (nx < 0 + sd) {
      nx = 0;
    // right
    if (nx > size.getWidth() - evt.getComponent().getWidth() - sd) {
      nx = (int) size.getWidth() - evt.getComponent().getWidth();
    // bottom
    if (ny > size.getHeight() - evt.getComponent().getHeight() - sd) {
      ny = (int) size.getHeight() - evt.getComponent().getHeight();
    // make sure we don't get into a recursive loop when the
    // set location generates more events
    locked = true;
    evt.getComponent().setLocation(nx, ny);
    locked = false;

  public static void main(String[] args) {
    JFrame frame = new JFrame("");
    JLabel label = new JLabel("Move this window's title bar to demonstrate screen edge snapping.");

    frame.addComponentListener(new WindowSnapper());


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