浏览图像文件并使用Java Swing显示它
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";
}
}
回答：
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));
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