我在单击按钮并在“选择文件对话框”中选择图像文件后尝试显示图像时遇到问题。
最初，我设法在 中显示所选图像JLabel，但后来我创建了一个单独的ActionListener，我认为从那时起它开始出错。无论我选择什么图像，JLabel都不会显示它。
我对其进行了调试，并确保文件选择器确实将图像传递给ImageIcon，JLabel确实从 获取值，但即使在和ImageIcon之后也不显示图像。revalidate()repaint()
在这里，我附上了我的代码供您参考！
（我修剪了代码以使外观干净，所以可能有一些括号没用）
package com.xxx.LoyalCardManager;
import java.awt.EventQueue;
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.sql.SQLException;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JSeparator;
import javax.swing.JTextField;
import javax.swing.filechooser.FileFilter;
public class LoyalCardManagerMain implements ActionListener{
private JFrame frame;
private DatabaseHandler db = new DatabaseHandler();
private JLabel labelPic;
private JButton buttonPic;
private File picFile = new File("");
private BufferedImage image;
/**
* Launch the application.
* @throws SQLException
* @throws ClassNotFoundException
*/
public static void main(String[] args) throws SQLException, ClassNotFoundException {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
LoyalCardManagerMain window = new LoyalCardManagerMain();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}
/**
* Create the application.
*/
public LoyalCardManagerMain() {
// Database initialisation
initDatabase();
// Draw GUI
frame = new JFrame();
frame.setBounds(100, 100, 619, 487);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
buttonPic = new JButton("Click to Choose Pic");
buttonPic.setBounds(415, 252, 166, 29);
frame.getContentPane().add(buttonPic);
buttonPic.setEnabled(false);
buttonPic.setActionCommand("ChoosePic");
buttonPic.addActionListener(this);
labelPic = new JLabel();
labelPic.setBounds(415, 30, 167, 210);
frame.getContentPane().add(labelPic);
}
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
if (command.equals("ChoosePic")) {
//TODO Label now cannot display images.
JFileChooser chooser = new JFileChooser();
chooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
chooser.setAcceptAllFileFilterUsed(false);
chooser.setFileFilter(new FileFilter() {
public boolean accept (File f) {
String extension = Utils.getExtension(f);
if(extension != null) {
if (extension.equals(Utils.gif) ||
extension.equals(Utils.jpeg) ||
extension.equals(Utils.jpg) ||
extension.equals(Utils.png) ||
extension.equals(Utils.tif) ||
extension.equals(Utils.tiff)) {
return true;
}else{
return false;
}
}
return false;
}
public String getDescription() {
return "Image File (*.gif, *.jpeg, *.jpg, *.png, *.tif, *.tiff)";
}
});
int retVal = chooser.showOpenDialog(frame);
if (retVal == JFileChooser.APPROVE_OPTION) {
picFile = chooser.getSelectedFile();
try {
image = ImageIO.read(picFile);
} catch (IOException e) {
e.printStackTrace();
}
// Calculate the pic's ratio and do re-scale
double ratio = (double) labelPic.getWidth() / (double) labelPic.getHeight();
// Do image scale, scaledW is the new Width, and LabelPic.getHeight is the new Height.
int scaledW = (int) (image.getHeight() * ratio);
image = new BufferedImage(scaledW, labelPic.getHeight(), BufferedImage.SCALE_FAST);
ImageIcon icon = new ImageIcon(image);
labelPic.setVisible(true);
labelPic.setIcon(icon);
labelPic.revalidate();
labelPic.repaint();
}
}
}
}
我还参考了其他类似的问题：
外部站点：JFIleChooser 将图像打开到 JLabel
以及 Java 教程文档 如何使用按钮、复选框和单选按钮
但我仍然无法弄清楚为什么 JLabel 不显示所选图像。
感谢热心帮忙的小伙伴们！