在较小的JFrame / Applet上显示大图像

Question

I have a pretty big image that I want to display on my JFrame and applet, the JFrame/Applet is 765x503 in size but the image is way larger. I need a way to display the image in real size. How can I make it so I can move the screen around to display some of the image and be able to move around the image?

I want to be able to drag the screen around, not use Scrollbars.

Answer 1

JScrollPane可能是您需要的。.添加垂直和水平滚动

Answer 2

The basic idea is you need to provide some kind of offset that should be applied to the image to be drawn.

When the user presses the mouse button at a point on the image, you record the click point. When the drag the mouse, you delta the difference. This gives you the amount the offset is to be moved. Based on the original position, you simply add this difference to the and generate a new offset.

There are other ways to do it, but generally, this is the method I use.

I've also added code to check to see if the drag would put the image out of bounds of the viewable area, you'll have to decide if you want to use it...

import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class BigImage {

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

    public BigImage() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage bg;
        private Point offset = new Point(0, 0);

        public TestPane() {
            try {
                bg = ImageIO.read(new File("/path/to/image"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            MouseAdapter ma = new MouseAdapter() {
                private Point clickPoint;
                private Point origin;

                @Override
                public void mousePressed(MouseEvent e) {
                    setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR));
                    clickPoint = e.getPoint();
                    origin = new Point(offset);
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    setCursor(Cursor.getDefaultCursor());
                    clickPoint = null;
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    int x = e.getPoint().x - clickPoint.x;
                    int y = e.getPoint().y - clickPoint.y;
                    offset.x = origin.x + x;
                    offset.y = origin.y + y;

                    if (offset.x > 0) {
                        offset.x = 0;
                    }
                    if (offset.x + bg.getWidth() < getWidth()) {
                        offset.x = -bg.getWidth() + getWidth();
                    }

                    if (offset.y > 0) {
                        offset.y = 0;
                    }
                    if (offset.y + bg.getHeight() < getHeight()) {
                        offset.y = -bg.getHeight() + getHeight();
                    }
                    repaint();
                }
            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(800, 600);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (bg != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                g2d.drawImage(bg, offset.x, offset.y, this);
                g2d.dispose();
            }
        }
    }
}