我正在用Swing编写Java GUI程序。该界面如下所示：

当用户单击右侧的图片之一时，我希望它的一个小的预览显示在左上角的橙色区域中。我通过SwingWorker线程从计算机上的目录中提取所有图像文件。在SwingWorker的done()方法中，我向每个对象添加了mouseClicked侦听器(我创建的类中的TaggableImage对象。它具有BufferedImage并扩展了JComponent，覆盖了paintComponent()方法)。在mouseClicked侦听器中，我调用橙色面板的add()方法并将其传递给TaggableImage。

我的问题：

当我单击其中一张图像时，它不会被添加到橙色面板中，并且会从右侧面板中消失。如果单击所有图像，则会在右侧面板空白。为什么会这样？

这是我的整个SwingWorker线程：

SwingWorker, Void> loadImagesAsyncWorker = new SwingWorker, Void>() {

ArrayList img_list = new ArrayList();

@Override

protected ArrayList doInBackground() throws Exception {

File currentDirectory = new File(".");

getFileInDirectory(currentDirectory);

return null;

}

// recursively get all files in this directory and child directories

private void getFileInDirectory(File cd) {

File[] file_list = cd.listFiles();

for (File f : file_list) {

if (f.isDirectory()) {

getFileInDirectory(f);

} else if (f.isFile()) {

BufferedImage bf = null;

String extension ="";

int i = f.getName().lastIndexOf('.');

int p = Math.max(f.getName().lastIndexOf('/'), f.getName()

.lastIndexOf('\'));

if (i > p) {

extension = f.getName().substring(i + 1);

}

System.out.println(f.getName());

if (extension.equals("jpg")) {

try {

bf = ImageIO.read(f);

TaggableImage ti = new TaggableImage(bf);

img_list.add(ti);

} catch (IOException e) {

}

}

}

}

}

public void done() {

for (TaggableImage ti : img_list) {

final TaggableImage final_ti = ti;

ti.addMouseListener(new MouseAdapter() {

public void mouseClicked(MouseEvent e) {

final_ti.setMaximumSize(new Dimension(30, 30));

BorderLayout layout = (BorderLayout) getContentPane()

.getLayout();

if (layout.getLayoutComponent(BorderLayout.CENTER) != null) {

img_prev_panel.remove(layout

.getLayoutComponent(BorderLayout.CENTER));

}

//img_prev_panel = the orange panel

img_prev_panel.add(final_ti, BorderLayout.CENTER);

});

}

}

};

这是我的TaggableImage类：

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.awt.image.ColorModel;

import java.awt.image.WritableRaster;

import javax.swing.JComponent;

public class TaggableImage extends JComponent {

private static final long serialVersionUID = 1L;

private BufferedImage bufferedImage;

private int height;

private int width;

public TaggableImage(BufferedImage bufferedImage) {

this.bufferedImage = bufferedImage;

}

public TaggableImage(BufferedImage bufferedImage, int width, int height) {

this.bufferedImage = bufferedImage;

this.width = width;

this.height = height;

}

@Override

protected void paintComponent(Graphics g) {

super.paintComponent(g);

g.drawImage(bufferedImage, 0, 0, null);

}

}

考虑发布MCVE。 请注意，一个组件只能有一个父级。 重新设定父级时，将从旧父级中删除该组件。 因此，当您将组件添加到img_prev_panel时，将从另一个容器中将其删除。

有没有一种方法可以将一个组件复制到另一个组件，同时为副本提供新的父对象？

您可以共享图像，在一个组件中显示缩略图版本，在另一个组件中显示完整尺寸。

我为此找到了Thumbnailator。

考虑在右侧面板上使用JList来利用灵活的布局选项和选择处理，如下所示。

import java.awt.Component;

import java.awt.Dimension;

import java.awt.EventQueue;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.GridLayout;

import java.awt.RenderingHints;

import java.awt.image.BufferedImage;

import javax.swing.BorderFactory;

import javax.swing.DefaultListCellRenderer;

import javax.swing.DefaultListModel;

import javax.swing.Icon;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JList;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JSplitPane;

import javax.swing.ListSelectionModel;

import javax.swing.UIManager;

import javax.swing.event.ListSelectionEvent;

import javax.swing.event.ListSelectionListener;

/**

* @see https://stackoverflow.com/a/25170471/230513

*/

public class ListDisplayPanel {

private static final Icon icon = UIManager.getIcon("html.pendingImage");

private ListPanel listPanel = new ListPanel();

private DisplayPanel displayPanel = new DisplayPanel();

private class DisplayPanel extends JPanel {

private static final int SIZE = 256;

private JLabel label = new JLabel();

public DisplayPanel() {

this.add(label);

}

@Override

protected void paintComponent(Graphics g) {

super.paintComponent(g);

BufferedImage img = new BufferedImage(icon.getIconWidth(), icon.getIconHeight(), BufferedImage.TYPE_INT_ARGB);

Graphics2D temp = (Graphics2D) img.getGraphics();

icon.paintIcon(this, temp, 0, 0);

temp.dispose();

Graphics2D g2d = (Graphics2D) g;

g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

g2d.drawImage(img, 0, 0, getWidth(), getHeight(), this);

}

@Override

public Dimension getPreferredSize() {

return new Dimension(SIZE, SIZE);

}

}

private class ListPanel extends JPanel {

private static final int N = 5;

private DefaultListModel dlm = new DefaultListModel();

private JList list = new JList(dlm);

public ListPanel() {

super(new GridLayout());

for (int i = 0; i < N * N; i++) {

String name ="Cell-" + String.format("%02d", i);

dlm.addElement(name);

}

list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

list.setLayoutOrientation(JList.HORIZONTAL_WRAP);

list.setVisibleRowCount(N);

list.setCellRenderer(new ListRenderer());

list.addListSelectionListener(new SelectionHandler());

this.add(list);

}

private class ListRenderer extends DefaultListCellRenderer {

@Override

public Component getListCellRendererComponent(JList list,

Object value, int index, boolean isSelected, boolean cellHasFocus) {

JLabel label = (JLabel) super.getListCellRendererComponent(

list, value, index, isSelected, cellHasFocus);

label.setBorder(BorderFactory.createEmptyBorder(N, N, N, N));

label.setIcon(icon);

label.setHorizontalTextPosition(JLabel.CENTER);

label.setVerticalTextPosition(JLabel.BOTTOM);

return label;

}

}

private class SelectionHandler implements ListSelectionListener {

@Override

public void valueChanged(ListSelectionEvent e) {

if (!e.getValueIsAdjusting()) {

displayPanel.label.setText((String) dlm.getElementAt(e.getLastIndex()));

}

}

}

}

private void display() {

JFrame f = new JFrame("Test");

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JSplitPane jsp = new JSplitPane();

jsp.setRightComponent(new JScrollPane(listPanel));

jsp.setLeftComponent(displayPanel);

f.add(jsp);

f.pack();

f.setLocationRelativeTo(null);

f.setVisible(true);

}

public static void main(String[] args) {

EventQueue.invokeLater(() -> {

new ListDisplayPanel().display();

});

}

}

或者，让displayPanel包含SelectionHandler。