java - 如何从 JFileChooser 中放入图像？

Question

我在使用 Graphics 将图像放入 jPanel 时遇到问题。我有下一个代码:

    JFileChooser navegador = new JFileChooser();
    if (navegador.showOpenDialog(null) == 0) {
        try {
            BufferedImage imagenAbrir = ImageIO.read(navegador.getSelectedFile());
            lienzo.paintComponents(imagenAbrir.getGraphics());
        } catch (IOException e) {
            JOptionPane.showMessageDialog(this, "Ocurriò un error al guardar la imàgen");
        }
    }

代码是按钮的一部分，用户可以从任何路径选择图像，但它不会在面板中显示任何内容。可能是什么问题？

Answer 1

我认为你必须用 BufferedImage 对象而不是 Graphics 对象来改变你的方法

@Override
            public void actionPerformed(ActionEvent e) {
                JFileChooser navegador = new JFileChooser();
                if (navegador.showOpenDialog(null) == 0) {
                    try {
                        BufferedImage imagenAbrir = ImageIO.read(navegador.getSelectedFile());
                        //drawPan.paintComponents(imagenAbrir.getGraphics());
                        drawPan.drawImage(imagenAbrir);
                    } catch (IOException ie) {
                        JOptionPane.showMessageDialog(null, "Ocurriò un error al guardar la imàgen");
                    }
                }
            }

然后，如果要绘制图像，请自行创建自定义的 JPanel 类。每次在代码中调用 repaint 方法时，都会自动调用 JComponent 的 paintCompoent 方法。

final class ImagePane extends JPanel {

            private static final long serialVersionUID = 1L;
            private BufferedImage myImage;

            public ImagePane(final BufferedImage myImage) {
                this.myImage = myImage;
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(240, 220);
            }

            public void drawImage(BufferedImage img)
            {
                this.myImage = img;
                repaint();
            }

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                if (myImage != null) {
                    Graphics2D g2d = (Graphics2D) g.create();
                    int x = (getWidth() - myImage.getWidth()) / 2;
                    int y = (getHeight() - myImage.getHeight()) / 2;
                    g2d.drawImage(myImage, x, y, this);
                    g2d.dispose();
                }
            }

        }

这里是完整的源代码。

public class JFileChooserTest {

    static Runnable doRun = new Runnable()
    {
        final class ChooseAction implements ActionListener
        {
            final ImagePane drawPan;

            ChooseAction(final ImagePane drawPan)
            {
                this.drawPan = drawPan;
            }


            @Override
            public void actionPerformed(ActionEvent e) {
                JFileChooser navegador = new JFileChooser();
                if (navegador.showOpenDialog(null) == 0) {
                    try {
                        BufferedImage imagenAbrir = ImageIO.read(navegador.getSelectedFile());
                        //drawPan.paintComponents(imagenAbrir.getGraphics());
                        drawPan.drawImage(imagenAbrir);
                    } catch (IOException ie) {
                        JOptionPane.showMessageDialog(null, "Ocurriò un error al guardar la imàgen");
                    }
                }
            }

        }

        final class ImagePane extends JPanel {

            private static final long serialVersionUID = 1L;
            private BufferedImage myImage;

            public ImagePane(final BufferedImage myImage) {
                this.myImage = myImage;
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(240, 220);
            }

            public void drawImage(BufferedImage img)
            {
                this.myImage = img;
                repaint();
            }

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                if (myImage != null) {
                    Graphics2D g2d = (Graphics2D) g.create();
                    int x = (getWidth() - myImage.getWidth()) / 2;
                    int y = (getHeight() - myImage.getHeight()) / 2;
                    g2d.drawImage(myImage, x, y, this);
                    g2d.dispose();
                }
            }

        }

        @Override
        public void run() {
            final JFrame frame = new JFrame();
            //frame.setSize(new Dimension(300,400));

            JPanel lienzo = new JPanel();
            lienzo.setLayout(new BorderLayout());

            ImagePane drawPan = new ImagePane(null);
            JButton drawMe = new JButton("draw me");
            lienzo.add(drawMe, BorderLayout.NORTH);
            lienzo.add(drawPan, BorderLayout.CENTER);

            frame.add(lienzo);

            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);

            drawMe.addActionListener(new ChooseAction(drawPan));
        }

    };

    public static void main(String[] args)
    {

        SwingUtilities.invokeLater(doRun);

    }
}

希望对您有所帮助。