Java JFrame为什么不显示图片？

Question

在createWorkPanel()方法中，我创建了一个Label并在其中放置了图片，但是该图片未显示在屏幕上。也许有人知道为什么，请告诉我？

Here is my code：

import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;

public class MainWindow extends JFrame {

    private JButton button1;

    public MainWindow() throws IOException
    {

        setLayout(new BorderLayout());
        createWorkPanel();
        setTitle("Графический дизайнер");
        //setDefaultLookAndFeelDecorated(true);
         setSize(1000,600);
       // setLocation(400,100);
       // setVisible(true);
       // pack(); // automatically size the window to fit its components
        setLocationRelativeTo(null); // center this window on the screen
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public void createWorkPanel() throws IOException
    {

        setLayout(new FlowLayout());
        button1 = new JButton("Load Images");
        button1.setActionCommand("Button 1 was prassed!");
        add(button1);
        ActionListener  actionListener = new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {

                File fImg = MyFileChooser.chooseFile("Image Files (png & jpg)", "png", "jpg");
                if (fImg != null)
                {
                    JLabel background=new JLabel(new ImageIcon(fImg.getAbsolutePath()));
                   // background.setLayout(new FlowLayout());
                    add(background);
                    System.out.println(" файл создан");
                }
            }
        };

        button1.addActionListener(actionListener);

    }

    public static  void main (String [] args) throws IOException {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    new MainWindow ().setVisible(true);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}


class MyFileChooser {
    public static File chooseFile(String description, String... extensions) {
        JFileChooser chooser = new JFileChooser();
        FileNameExtensionFilter filter = new FileNameExtensionFilter(description, extensions);
        chooser.setFileFilter(filter);
        int returnVal = chooser.showOpenDialog(null);
        if(returnVal == JFileChooser.APPROVE_OPTION) {
            File selectedFile = chooser.getSelectedFile();
            System.out.println("You chose to open this file: " + selectedFile.getAbsolutePath());
            return selectedFile;
        } else {
            return null;
        }
    }
}

Answer 1

遵循以下代码。

if (fImg != null) {
    JLabel background = new JLabel(new ImageIcon(fImg.getAbsolutePath()));
    add(background);
    MainWindow.this.revalidate();
}

添加MainWindow.this.revalidate();应该会有所帮助。