Question

我想要在我的JFrame和applet上显示一个非常大的图像，JFrame / Applet的大小是765x503，但图像更大。我需要一种以实际尺寸显示图像的方法。我怎样才能做到这一点，我可以移动屏幕来显示一些图像，并能够在图像周围移动？

我希望能够拖动屏幕，而不是使用滚动条。

Answer 1

JScrollPane可能是您需要的......添加垂直和水平滚动

Answer 2

基本思路是你需要提供一些应该应用于要绘制的图像的偏移。

当用户在图像上的某个点按下鼠标按钮时，您会记录点击点。当拖动鼠标时，你差异化了。这为您提供了移动偏移量。根据原始位置，您只需将此差异添加到并生成新的偏移量。

还有其他方法可以做到，但一般来说，这是我使用的方法。

我还添加了代码来检查拖动是否会使图像超出可视区域的范围，您必须决定是否要使用它...

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();
            }
        }
    }
}

较小的JFrame / Applet上的大图像

2 个答案: