import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
/**
 * 用Java模擬出QQ桌面截圖功能
 */
public class Test extends JFrame {
 private static final long serialVersionUID = -267804510087895906L;
 private JButton button = null;
 private JLabel imgLabel = null;
 public Test() {
 button = new JButton("模擬屏幕（點右鍵退出）");
 button.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {
  try {
   new ScreenWindow(imgLabel);
  } catch (Exception e1) {
   JOptionPane.showConfirmDialog(null, "出現(xiàn)意外錯誤！", "系統(tǒng)提示", JOptionPane.DEFAULT_OPTION, JOptionPane.ERROR_MESSAGE);
  }
  }
 });
 JPanel pane = new JPanel();
 pane.setBackground(Color.WHITE);
 imgLabel = new JLabel();
 pane.add(imgLabel);
 JScrollPane spane = new JScrollPane(pane);
 this.getContentPane().add(button, BorderLayout.NORTH);
 this.getContentPane().add(spane);
 this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 this.setSize(300, 200);
 this.setLocationRelativeTo(null);
 this.setVisible(true);
 }
 public static void main(String[] args) {
 new Test();
 }
}
class ScreenWindow extends JFrame {
 private static final long serialVersionUID = -3758062802950480258L;
 private boolean isDrag = false;
 private int x = 0;
 private int y = 0;
 private int xEnd = 0;
 private int yEnd = 0;
 public ScreenWindow(final JLabel imgLabel) throws AWTException, InterruptedException {
 Dimension screenDims = Toolkit.getDefaultToolkit().getScreenSize();
 JLabel label = new JLabel(new ImageIcon(ScreenImage.getScreenImage(0, 0, screenDims.width, screenDims.height)));
 label.setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));
 label.addMouseListener(new MouseAdapter() {
  public void mouseClicked(MouseEvent e) {
  if (e.getButton() == MouseEvent.BUTTON3) {
   dispose();
  }
  }
  public void mousePressed(MouseEvent e) {
  x = e.getX();
  y = e.getY();
  }
  public void mouseReleased(MouseEvent e) {
  if (isDrag) {
   xEnd = e.getX();
   yEnd = e.getY();
   if(x > xEnd){
   int temp = x;
   x = xEnd;
   xEnd = temp;
   }
   if(y > yEnd){
   int temp = y;
   y = yEnd;
   yEnd = temp;
   }
   try {
   imgLabel.setIcon(new ImageIcon(ScreenImage.getScreenImage(x, y, xEnd - x, yEnd - y)));
   } catch (Exception ex) {
   JOptionPane.showConfirmDialog(null, "出現(xiàn)意外錯誤！", "系統(tǒng)提示", JOptionPane.DEFAULT_OPTION, JOptionPane.ERROR_MESSAGE);
   }
   dispose();
  }
  }
 });
 label.addMouseMotionListener(new MouseMotionListener() {
  public void mouseDragged(MouseEvent e) {
  if(!isDrag)
   isDrag = true;
  }
  public void mouseMoved(MouseEvent e) {
  /** 拖動過程的虛線選取框需自己實現(xiàn) */
  }
 });
 this.setUndecorated(true);
 this.getContentPane().add(label);
 this.setSize(screenDims.width, screenDims.height);
 this.setVisible(true);
 this.setExtendedState(JFrame.MAXIMIZED_BOTH);
 }
}
class ScreenImage {
 public static Image getScreenImage(int x, int y, int w, int h) throws AWTException, InterruptedException {
 Robot robot = new Robot();
 Image screen = robot.createScreenCapture(new Rectangle(x, y, w, h)).getScaledInstance(w, h, Image.SCALE_SMOOTH);
 MediaTracker tracker = new MediaTracker(new Label());
 tracker.addImage(screen, 1);
 tracker.waitForID(0);
 return screen;
 }
}