Question

使用Graphics将图像放入jPanel时出现问题。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中选择图像，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，如果您想绘制图像，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);

    }
}

我希望这会对你有所帮助。

Answer 2

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

基本上，这不是自定义绘画在Swing中的工作方式。永远不要自己致电paintComponent或paintComponents，这不是您的责任。

您要做的是通过其Graphics上下文

将图像绘制到组件

请查看Painting in AWT and Swing和Performing Custom Painting，了解有关绘画如何运作以及您如何使用它的详细信息

然后查看How to use lables以获取显示图像的简单解决方案

您还可以查看How to set a background picture in JPanel。它演示了使用JLabel和自定义组件来显示图像

Answer 3

那么，您想在显示某些基本图像的面板上添加图像吗？如果是这样，有一些技巧可以做到这一点。我在互联网上准备两张图片（恐怕这些是许可图片）

然后，现在我有三个按钮放在你的课上

JButton drawMe = new JButton("draw me");
JButton pickMe = new JButton("pick me");
JButton clearMe = new JButton("clear me");

我决定让DrawAction类重用三个动作命令，这些命令是一个draw，pick和clear。

drawMe.addActionListener(drawAct);
drawMe.setActionCommand("draw");
pickMe.addActionListener(drawAct);
pickMe.setActionCommand("pick");
clearMe.addActionListener(drawAct);
clearMe.setActionCommand("clear");

我们会再次看到ImagePane类。如果要在图像上添加图像，则应该从JComponent继承一个paintcomponent方法，无论您要使用哪个组件。

吸引我＆＃39;按钮是在清除bufferedimage类的数组列表的图像列表中的所有图像后设置基本图像。

public void drawImage(BufferedImage img)
{
    if (imageList.size() > 0) imageList.clear();
    imageList.add(img);
    repaint();
}

选择我＆＃39;按钮是将图像添加到图像列表的方法。

public void addImage(BufferedImage imagenAbrir) {
    imageList.add(imagenAbrir);
    repaint();
}

最后一个是清除按钮，刷新并清除图像列表中的所有图像缓冲区。

public void clearImage() {
     imageList.clear();
     isClear = true;
     repaint();
}

这是我在面板上清除图像的技巧，它是通过使用某种特定颜色（灰色）重新绘制画布（此时为jPanel）来完成的。主要方法，paintComponent如下..

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    if(isClear)
    {
        Graphics2D g2d = (Graphics2D) g.create();
        Rectangle2D rectangle = new Rectangle2D.Double(0,0,getWidth(),getHeight());
        g2d.setPaint(Color.GRAY);
        g2d.fill(rectangle);
        g2d.dispose();

        isClear = false;
        return;
    }


    if (imageList.size() > 0) {
        BufferedImage img = null;
        for(int i = 0; i < imageList.size(); i++)
        {
            img = imageList.get(i);
            Graphics2D g2d = (Graphics2D) g.create();
            int x = (getWidth() - img.getWidth()) / 2;
            int y = (getHeight() - img.getHeight()) / 2;
            g2d.drawImage(img, x, y, this);
            g2d.dispose();
        }
    }
}

最后，您阅读下面的代码，了解如何处理动作命令以及java的组件

@Override
public void actionPerformed(ActionEvent e) {

    if(e.getActionCommand().equals("draw"))
    {
        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, "Ocurrio un error al guardar la imagen");
            }
        }
    }
    else if(e.getActionCommand().equals("pick"))
    {
        JFileChooser navegador = new JFileChooser();
        if (navegador.showOpenDialog(null) == 0) {
            try {
                BufferedImage imagenAbrir = ImageIO.read(navegador.getSelectedFile());
                //drawPan.paintComponents(imagenAbrir.getGraphics());
                drawPan.addImage(imagenAbrir);
            } catch (IOException ie) {
                JOptionPane.showMessageDialog(null, "Ocurrio un error al guardar la imagen");
            }
        }
    }
    else if(e.getActionCommand().equals("clear"))
    {
        drawPan.clearImage();
    }
}

当您看到代码时，每次单击选择或绘制我按钮时都需要选择文件。

完整源代码

package com.tobee.ui.test;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class JFileChooserTest {

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

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


            @Override
            public void actionPerformed(ActionEvent e) {

                System.out.println(e.getActionCommand());

                if(e.getActionCommand().equals("draw"))
                {
                    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");
                        }
                    }
                }
                else if(e.getActionCommand().equals("pick"))
                {
                    JFileChooser navegador = new JFileChooser();
                    if (navegador.showOpenDialog(null) == 0) {
                        try {
                            BufferedImage imagenAbrir = ImageIO.read(navegador.getSelectedFile());
                            //drawPan.paintComponents(imagenAbrir.getGraphics());
                            drawPan.addImage(imagenAbrir);
                        } catch (IOException ie) {
                            JOptionPane.showMessageDialog(null, "Ocurriò un error al guardar la imàgen");
                        }
                    }
                }
                else if(e.getActionCommand().equals("clear"))
                {
                    drawPan.clearImage();
                }
            }

        }

        final class ImagePane extends JPanel {

            private static final long serialVersionUID = 1L;
            private boolean isClear;

            private List<BufferedImage> imageList;

            public ImagePane()
            {
                imageList = new ArrayList<BufferedImage>();
                isClear = false;
            }

            public void clearImage() {
                imageList.clear();
                isClear = true;
                repaint();
            }

            public void addImage(BufferedImage imagenAbrir) {
                imageList.add(imagenAbrir);
                repaint();
            }

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

            public void drawImage(BufferedImage img)
            {
                if (imageList.size() > 0) imageList.clear();
                imageList.add(img);
                repaint();
            }

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);

                if(isClear)
                {
                    Graphics2D g2d = (Graphics2D) g.create();
                    Rectangle2D rectangle = new Rectangle2D.Double(0,0,getWidth(),getHeight());
                    g2d.setPaint(Color.GRAY);
                    g2d.fill(rectangle);
                    g2d.dispose();

                    isClear = false;
                    return;
                }


                if (imageList.size() > 0) {
                    BufferedImage img = null;
                    for(int i = 0; i < imageList.size(); i++)
                    {
                        img = imageList.get(i);
                        Graphics2D g2d = (Graphics2D) g.create();
                        int x = (getWidth() - img.getWidth()) / 2;
                        int y = (getHeight() - img.getHeight()) / 2;
                        g2d.drawImage(img, x, y, this);
                        g2d.dispose();
                    }
                }
            }

        }

        @Override
        public void run() {
            final JFrame frame = new JFrame();

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


            JPanel optionPan = new JPanel();
            ImagePane drawPan = new ImagePane();
            JButton drawMe = new JButton("draw me");
            JButton pickMe = new JButton("pick me");
            JButton clearMe = new JButton("clear me");

            DrawAction drawAct = new DrawAction(drawPan);

            optionPan.add(drawMe);
            optionPan.add(pickMe);
            optionPan.add(clearMe);

            lienzo.add(optionPan, BorderLayout.NORTH);
            lienzo.add(drawPan, BorderLayout.CENTER);

            frame.add(lienzo);

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

            drawMe.addActionListener(drawAct);
            drawMe.setActionCommand("draw");
            pickMe.addActionListener(drawAct);
            pickMe.setActionCommand("pick");
            clearMe.addActionListener(drawAct);
            clearMe.setActionCommand("clear");
        }

    };

    public static void main(String[] args)
    {

        SwingUtilities.invokeLater(doRun);

    }
}

如何从JFileChooser中放入图像？

3 个答案: