import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;

/**
 * 捕获屏幕，屏幕截图工具
 */
public class ScreenCaptureFrame extends JFrame implements ActionListener {

    private ScreenCaptureUtil scrCaptureUtil = null;// 捕获屏幕的工具类
    private PaintCanvas canvas = null;// 画布，用于画捕获到的屏幕图像

    public ScreenCaptureFrame() {
        super("Screen Capture");
        init();
    }

    /**
     * 初始化
     */
    private void init() {

        scrCaptureUtil = new ScreenCaptureUtil();// 创建抓屏工具
        canvas = new PaintCanvas(scrCaptureUtil);// 创建画布

        Container c = this.getContentPane();
        c.setLayout(new BorderLayout());
        c.add(canvas, BorderLayout.CENTER);

        JButton capButton = new JButton("抓 屏");
        c.add(capButton, BorderLayout.SOUTH);
        capButton.addActionListener(this);
        this.setSize(400, 400);
        this.setVisible(true);
        this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    }

    public void actionPerformed(ActionEvent e) {// 点击“抓屏”按钮时，在画布上画屏幕图像
        canvas.drawScreen();
    }

    public static void main(String[] args) {
        new ScreenCaptureFrame();
    }
}

/**
 * 抓屏工具类
 */
class ScreenCaptureUtil {
    private Robot robot = null;// 抓屏的主要工具类
    private Rectangle scrRect = null;// 屏幕的矩形图像

    public ScreenCaptureUtil() {
        try {
            robot = new Robot();// 创建一个抓屏工具
        } catch (Exception ex) {
            System.out.println(ex.toString());
        }
        // 获取屏幕的矩形图像
        Dimension scrSize = Toolkit.getDefaultToolkit().getScreenSize();
        scrRect = new Rectangle(0, 0, scrSize.width, scrSize.height);
    }

    /**
     * 抓屏方法
     * 
     * @return 返回一个图像
     */
    public BufferedImage captureScreen() {
        BufferedImage scrImg = null;
        try {
            scrImg = robot.createScreenCapture(scrRect);// 抓的是全屏图
        } catch (Exception e) {
            System.out.println(e.toString());
        }
        return scrImg;
    }
}

/**
 * 画布类，用于显示抓屏得到的图像
 */
class PaintCanvas extends JPanel {
    private ScreenCaptureUtil scrCaptureUtil = null;// 抓屏工具
    private BufferedImage scrImg = null;// 待画的图像　

    public PaintCanvas(ScreenCaptureUtil screenUtil) {
        this.scrCaptureUtil = screenUtil;
    }

    /**
     * 重载JPanel的paintComponent，用于画背景
     */
    protected void paintComponent(Graphics g) {
        if (scrImg != null) {
            int iWidth = this.getWidth();
            int iHeight = this.getHeight();
            g.drawImage(scrImg, 0, 0, iWidth, iHeight, 0, 0, scrImg.getWidth(),
                    scrImg.getHeight(), null);
        }
    }

    /**
     * 画屏幕图像的方法
     */
    public void drawScreen() {
        Graphics g = this.getGraphics();
        scrImg = scrCaptureUtil.captureScreen();// 抓屏，获取屏幕图像
        if (scrImg != null) {
            this.paintComponent(g);// 画图
        }
        g.dispose();// 释放资源
    }

}