在Java Swing中浏览图像文件并显示

Question

我的问题是，在点击 Browse 按钮后，它会显示目录中所有的文件供选择，然后所选图片会正确地在 GUI 中显示。但是当我第二次点击浏览按钮时，它仅显示旧图片，而不是新的图片。请帮助我解决这个问题。

为了参考，我上传了 UI。

package GUI;

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Graphics2D;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JLabel;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;


@SuppressWarnings("serial")
public class MainAppFrame extends JFrame {

    private JPanel contentPane;
    File targetFile;
    BufferedImage targetImg;
    public JPanel panel,panel_1;
    private static final int baseSize = 128;
    private static final String basePath =
            "C:\\Documents and Settings\\Administrator\\Desktop\\Images";

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MainAppFrame frame = new MainAppFrame();
                    frame.setVisible(true);
                    frame.setResizable(false);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public MainAppFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 550, 400);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(new BorderLayout(0, 0));
        
        panel = new JPanel();
        panel.setBorder(new javax.swing.border.LineBorder(new java.awt.Color(0, 0, 0), 1, true));
        contentPane.add(panel, BorderLayout.WEST);
        
        JButton btnBrowse = new JButton("Browse");
        btnBrowse.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                browseButtonActionPerformed(e);
            }
        });
        
        JLabel lblSelectTargetPicture = new JLabel("Select target picture..");
        
        JButton btnDetect = new JButton("Detect");
        btnDetect.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
            }
        });
        
        JButton btnAddDigit = new JButton("Add Digit");
        btnAddDigit.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
            }
        });
        
        JButton button = new JButton("Recognize");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
            }
        });
        
        panel_1 = new JPanel();
        panel_1.setBorder(new javax.swing.border.LineBorder(new java.awt.Color(0, 0, 0), 1, true));

        GroupLayout gl_panel = new GroupLayout(panel);
        gl_panel.setHorizontalGroup(
            gl_panel.createParallelGroup(Alignment.LEADING)
                .addGroup(gl_panel.createSequentialGroup()
                    .addGap(6)
                    .addGroup(gl_panel.createParallelGroup(Alignment.LEADING)
                        .addGroup(gl_panel.createSequentialGroup()
                            .addComponent(lblSelectTargetPicture)
                            .addGap(6)
                            .addComponent(btnBrowse))
                        .addGroup(gl_panel.createSequentialGroup()
                            .addGap(10)
                            .addComponent(btnDetect)
                            .addGap(18)
                            .addComponent(btnAddDigit))))
                .addGroup(gl_panel.createSequentialGroup()
                    .addGap(50)
                    .addComponent(button))
                .addGroup(gl_panel.createSequentialGroup()
                    .addContainerGap()
                    .addComponent(panel_1, GroupLayout.PREFERRED_SIZE, 182, GroupLayout.PREFERRED_SIZE))
        );
        gl_panel.setVerticalGroup(
            gl_panel.createParallelGroup(Alignment.LEADING)
                .addGroup(gl_panel.createSequentialGroup()
                    .addGroup(gl_panel.createParallelGroup(Alignment.LEADING)
                        .addGroup(gl_panel.createSequentialGroup()
                            .addGap(7)
                            .addComponent(lblSelectTargetPicture))
                        .addGroup(gl_panel.createSequentialGroup()
                            .addGap(3)
                            .addComponent(btnBrowse)))
                    .addGap(18)
                    .addComponent(panel_1, GroupLayout.PREFERRED_SIZE, 199, GroupLayout.PREFERRED_SIZE)
                    .addGap(22)
                    .addGroup(gl_panel.createParallelGroup(Alignment.BASELINE)
                        .addComponent(btnDetect)
                        .addComponent(btnAddDigit))
                    .addGap(18)
                    .addComponent(button)
                    .addContainerGap())
        );
        
        panel.setLayout(gl_panel);
    }
    public BufferedImage rescale(BufferedImage originalImage)
    {
        BufferedImage resizedImage = new BufferedImage(baseSize, baseSize, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = resizedImage.createGraphics();
        g.drawImage(originalImage, 0, 0, baseSize, baseSize, null);
        g.dispose();
        return resizedImage;
    }
    public void setTarget(File reference)
    {
        try {
            targetFile = reference;
            targetImg = rescale(ImageIO.read(reference));
        } catch (IOException ex) {
            Logger.getLogger(MainAppFrame.class.getName()).log(Level.SEVERE, null, ex);
        }
        
        panel_1.setLayout(new BorderLayout(0, 0));
        panel_1.add(new JLabel(new ImageIcon(targetImg))); 
        setVisible(true);
    }
    private void browseButtonActionPerformed(java.awt.event.ActionEvent evt) {
        JFileChooser fc = new JFileChooser(basePath);
        fc.setFileFilter(new JPEGImageFileFilter());
        int res = fc.showOpenDialog(null);
        // We have an image!
        try {
            if (res == JFileChooser.APPROVE_OPTION) {
                File file = fc.getSelectedFile();
                setTarget(file);
            } // Oops!
            else {
                JOptionPane.showMessageDialog(null,
                        "You must select one image to be the reference.", "Aborting...",
                        JOptionPane.WARNING_MESSAGE);
            }
        } catch (Exception iOException) {
        }
    
    }
}




//JPEGImageFileFilter.java

package GUI;

import java.io.File;

import javax.swing.filechooser.FileFilter;

/*
* This class implements a generic file name filter that allows the listing/selection
* of JPEG files.
*/
public class JPEGImageFileFilter extends FileFilter implements java.io.FileFilter
 {
 public boolean accept(File f)
   {
   if (f.getName().toLowerCase().endsWith(".jpeg")) return true;
   if (f.getName().toLowerCase().endsWith(".jpg")) return true;
   if(f.isDirectory())return true;
   return false;
  }
 public String getDescription()
   {
   return "JPEG files";
   }

} 

- user1844951

---

你能更新一下你的工作代码吗？ - Java Man

1个额外建议，软件包名称始终使用小写。 - Dharmendrasinh Chudasama

Answer 1

每次选择新图片时，您都会在这里不必要地创建组件并出现错误：

public void setTarget(File reference) {
    //....
    panel_1.setLayout(new BorderLayout(0, 0));
    panel_1.add(new JLabel(new ImageIcon(targetImg))); 
    setVisible(true);

相反，我建议您在选择任何文件/图像之前，就从一开始就创建所有这些组件，然后使用此方法从图像创建ImageIcon，然后仅使用此图标将已存在的JLabel的图标设置为图标，而不是新的JLabel。要做到这一点，只需调用myLabel.setIcon(new ImageIcon(targetImg));

- Hovercraft Full Of Eels

---

非常感谢您的回复 :) 您说的方法很有效。但是图像没有居中显示。您能帮我吗？ 我像这样做了... label = new JLabel(); panel_1.add(label); ..... label.setIcon(new ImageIcon(targetImg)); - user1844951

label.setHorizontalAlignment(SwingConstants.CENTER);我使用了上述代码行，谢谢 @Hovercraft Full Of Eels 的帮助。 - user1844951

@HovercraftFullOfEels 在设置图像后第一次无法工作？你能更新你的代码吗？ - Java Man

Answer 2

使用类似于 ImageViewer.setImage(Image) 的方法创建一个 ImageViewer，在 JLabel 中显示图片。

ImageViewer

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.util.Random;

public class ImageViewer {
    
    JPanel gui;
    /** Displays the image. */
    JLabel imageCanvas;

    /** Set the image as icon of the image canvas (display it). */
    public void setImage(Image image) {
        imageCanvas.setIcon(new ImageIcon(image));
    }
    
    public void initComponents() {
        if (gui==null) { 
            gui = new JPanel(new BorderLayout());
            gui.setBorder(new EmptyBorder(5,5,5,5));
            imageCanvas = new JLabel();
            
            JPanel imageCenter = new JPanel(new GridBagLayout());
            imageCenter.add(imageCanvas);
            JScrollPane imageScroll = new JScrollPane(imageCenter);
            imageScroll.setPreferredSize(new Dimension(300,100));
            gui.add(imageScroll, BorderLayout.CENTER);
        }
    }
    
    public Container getGui() {
        initComponents();
        return gui;
    }
    
    public static Image getRandomImage(Random random) {
        int w = 100 + random.nextInt(400);
        int h = 50 + random.nextInt(200);
        BufferedImage bi = new BufferedImage(
                w,h,BufferedImage.TYPE_INT_RGB);
        
        return bi;
    }

    public static void main(String[] args) throws Exception {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame("Image Viewer");
                // TODO Fix kludge to kill the Timer
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            
                final ImageViewer viewer = new ImageViewer();
                f.setContentPane(viewer.getGui());
                
                f.pack();
                f.setLocationByPlatform(true);
                f.setVisible(true);

                ActionListener animate = new ActionListener() {

                    Random random = new Random();
                    
                    @Override
                    public void actionPerformed(ActionEvent arg0) {
                        viewer.setImage(getRandomImage(random));
                    }
                };
                Timer timer = new Timer(1500,animate);
                timer.start();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

- Andrew Thompson

Answer 3

我修改了你的代码，希望它能够满足你的要求。我使用MigLayout（这是一个布局管理器）来排列组件。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import net.miginfocom.swing.MigLayout;

public class MyFileChooser
{

JFrame frame; 
JPanel panel;
JButton btnBrowse;
JButton change;
JLabel imglabel;

File targetFile;
BufferedImage targetImg;
private static final int baseSize = 128;
private static final String basePath ="/images/fimage";
JPanel panel_1;
ImageIcon icon;
public MyFileChooser() 
{
    // TODO Auto-generated constructor stub
    frame =new JFrame();
    frame.setLayout(new MigLayout());

    frame.setSize(300, 300);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

     panel=new JPanel(new MigLayout());
     panel_1 = new JPanel();
     panel_1.setBorder(new javax.swing.border.LineBorder(new java.awt.Color(5, 5, 5), 1, true));

     panel_1.setBackground(Color.pink);

     btnBrowse=new JButton("browse");
     btnBrowse.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            browseButtonActionPerformed(e);
        }
    });

    change=new JButton("Delete");
    change.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) 
        {
            // TODO Auto-generated method stub
            changeButtonActionPerformed(e);

        }

        private void changeButtonActionPerformed(ActionEvent e) 
        {
            // TODO Auto-generated method stub

               imglabel.revalidate(); //ADD THIS AS WELL
               imglabel.repaint();  //ADD THIS AS WELL
               imglabel.setIcon(null);
               System.out.println("delete button activated");

        }
    });


    imglabel=new JLabel("Image");
    imglabel.setSize(100, 100);
    imglabel.setBackground(Color.yellow);
    frame.add(panel_1,"span,pushx,pushy,growx,growy");
    frame.add(btnBrowse);
    frame.add(change,"");

    //frame.pack();



}

protected void browseButtonActionPerformed(ActionEvent e) 
{


    JFileChooser fc = new JFileChooser(basePath);
    fc.setFileFilter(new JPEGImageFileFilter());
    int res = fc.showOpenDialog(null);
    // We have an image!
    try {
        if (res == JFileChooser.APPROVE_OPTION) {
            File file = fc.getSelectedFile();
            imglabel.setIcon(null);
           setTarget(file);
        } // Oops!
        else {
            JOptionPane.showMessageDialog(null,
                    "You must select one image to be the reference.", "Aborting...",
                    JOptionPane.WARNING_MESSAGE);
        }
    } catch (Exception iOException) {
    }

}

public BufferedImage rescale(BufferedImage originalImage)
{
    BufferedImage resizedImage = new BufferedImage(baseSize, baseSize, BufferedImage.TYPE_INT_RGB);
    Graphics2D g = resizedImage.createGraphics();
    g.drawImage(originalImage, 0, 0, baseSize, baseSize, null);
    g.dispose();
    return resizedImage;
}
public void setTarget(File reference)
{

    try {
        targetFile = reference;
        targetImg = rescale(ImageIO.read(reference));
    } catch (IOException ex) {
       // Logger.getLogger(MainAppFrame.class.getName()).log(Level.SEVERE, null, ex);
    }

    panel_1.setLayout(new BorderLayout(0, 0));

    icon=new ImageIcon(targetImg);
    imglabel=new JLabel(icon);
    panel_1.add(imglabel); 

    frame.setVisible(true);
}
public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub

            new MyFileChooser();

        }
    });
}

}

JPEGImageFileFilter类，您可以将此类保留在同一包中

import java.io.File;

import javax.swing.filechooser.FileFilter;

public class JPEGImageFileFilter extends FileFilter implements    FileFilter           
{
public boolean accept(File f)
{
  if (f.getName().toLowerCase().endsWith(".jpeg")) return true;
  if (f.getName().toLowerCase().endsWith(".jpg")) return true;
 if(f.isDirectory())return true;
 return false;
}
public String getDescription()
{
  return "JPEG files";
}

} 

- Sachindra N. Pandey