如何在后台运行时使用Java程序

Question

当我按下键盘上的特定按钮时，我正在编写一个程序来捕获屏幕截图。我遇到的问题是，如果程序在后台运行，程序将不会拍摄我的屏幕截图。屏幕截图仅捕获我的程序是否位于前台。

我使用机器人类捕获并保存屏幕截图。我的节目如下......

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import java.awt.AWTException;
import java.awt.DefaultKeyboardFocusManager;
import java.awt.KeyEventDispatcher;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;

public class FullScreenCaptureExample{

    private static int num = 1;

    public static void main(String[] args) throws AWTException{

        final File file = new File("C:\\screenshots");
        final Robot rbt = new Robot();
        JFrame frame = new JFrame();

        frame.setVisible(true);
        frame.setBounds(100, 100, 190, 73);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        if(!file.exists()){
            file.mkdir();
        }

        KeyEventDispatcher dispatcher = new KeyEventDispatcher(){       
            public boolean dispatchKeyEvent(KeyEvent e){
                if (e.getKeyCode() == KeyEvent.VK_5){
                    try {
                        Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
                        BufferedImage screenshot = rbt.createScreenCapture(screenRect);
                        ImageIO.write(screenshot, "jpg", new File(file + "/" + num + ".jpg"));
                        num++;
                        System.out.println("screenshot taken");
                    } catch (Exception e1) {
                        e1.printStackTrace();
                    }
                }
                return false;
            }
        };

        DefaultKeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(dispatcher);
    }

}

我想知道是否有一个java类或其他方式来获取用户输入而不让程序在前台运行。

谢谢