浏览图像文件并使用Java Swing显示它

Question

我的问题是，单击Browse按钮后，它会显示目录中的所有文件供选择，然后所选的图像会正确显示在GUI中。但是，当我第二次单击“浏览”按钮时，它仅显示旧图像，而不显示新图像。请帮助我。

作为参考，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 =![enter image description here][1]
            "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";
   }

} 

Answer 1

每次选择新图像时，都在这里不必要地创建了组件，并且错误地出现在这里：

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

相反，我建议你在选择任何文件/图像之前，从一开始就创建所有这些组件，然后在此方法中，根据图像创建一个ImageIcon，然后简单地使用此Icon来设置已经存在的JLabel，而不是新的JLabel。只需调用myLabel.setIcon(new ImageIcon(targetImg));