Java screen capture App - How to?

问题

i am not a native english speaker so, firstly sorry for the grammar.

I want to do an app that capture a selected area of a screen and save it. I did a few research and i did the code down below.

My questions are:

1 - How can i open a pdf file in this app ? (i tried use a method but it didnt work. I dont know exactly where to put it on the code)

2 - How can i save the selected area in a new file ? (a image file : JPEG, JPG,png)

3 - [the complex part] right now, the code only "save" one selected area each time. I want to capture a lot of parts of screen and save this in the same image file. one beside the other. How can i do this ?

Java Code:

package javaapplication39;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;

public class ScreenCaptureRectangle {

    Rectangle captureRect;

    ScreenCaptureRectangle(final BufferedImage screen) {
        final BufferedImage screenCopy = new BufferedImage(
                screen.getWidth(),
                screen.getHeight(),
                screen.getType());
        final JLabel screenLabel = new JLabel(new ImageIcon(screenCopy));
        JScrollPane screenScroll = new JScrollPane(screenLabel);

        screenScroll.setPreferredSize(new Dimension(
                (int)(screen.getWidth()/3),
                (int)(screen.getHeight()/3)));

        JPanel panel = new JPanel(new BorderLayout());
        panel.add(screenScroll, BorderLayout.CENTER);

        final JLabel selectionLabel = new JLabel(
                "Drag a rectangle in the screen shot!");
        panel.add(selectionLabel, BorderLayout.SOUTH);

        repaint(screen, screenCopy);
        screenLabel.repaint();

        screenLabel.addMouseMotionListener(new MouseMotionAdapter() {

            Point start = new Point();

            @Override
            public void mouseMoved(MouseEvent me) {
                start = me.getPoint();
                repaint(screen, screenCopy);
                selectionLabel.setText("Start Point: " + start);
                screenLabel.repaint();
            }

            @Override
            public void mouseDragged(MouseEvent me) {
                Point end = me.getPoint();
                captureRect = new Rectangle(start,
                        new Dimension(end.x-start.x, end.y-start.y));
                repaint(screen, screenCopy);
                screenLabel.repaint();
                selectionLabel.setText("Rectangle: " + captureRect);
            }
        });

        JOptionPane.showMessageDialog(null, panel);

        System.out.println("Rectangle of interest: " + captureRect);
    }

    public void repaint(BufferedImage orig, BufferedImage copy) {
        Graphics2D g = copy.createGraphics();
        g.drawImage(orig,0,0, null);
        if (captureRect!=null) {
            g.setColor(Color.RED);
            g.draw(captureRect);
            g.setColor(new Color(255,255,255,150));
            g.fill(captureRect);
        }
        g.dispose();
    }

    public static void main(String[] args) throws Exception {
        Robot robot = new Robot();
        final Dimension screenSize = Toolkit.getDefaultToolkit().
                getScreenSize();
        final BufferedImage screen = robot.createScreenCapture(
                new Rectangle(screenSize));

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ScreenCaptureRectangle(screen);
            }
        });
    }
}

回答1:

1 - How can i open a pdf file in this app ? (i tried use a method but it didnt work. I dont know exactly where to put it on the code)

Take a look at How to Integrate with the Desktop Class

2 - How can i save the selected area in a new file ? (a image file : JPEG, JPG,png)

Take a look at Writing/Saving an Image

3 - [the complex part] right now, the code only "save" one selected area each time. I want to capture a lot of parts of screen and save this in the same image file. one beside the other. How can i do this ?

Is, as you say, a much more complex question. You will have to modify the code so that instead of displaying the panel in a JOptionPane, it shows it within a JFrame, you then need to be able to either monitor the mouseReleaseEvent or provide some kind of action, may be a toolbar or menu option, that allows the user to save the selection.

Have a look at How to Use Menus, How to Use Buttons, Check Boxes, and Radio Buttons, How to Write an Action Listeners and How to Use Tool Bars for more details.

As a side note, the code will only allow you to capture a single screen, you might consider something like Drawing a bounding rectangle to select what area to record which will allow you to capture the entire virtual desktop (multiple screeens)

来源：https://stackoverflow.com/questions/26538601/java-screen-capture-app-how-to