Question

我正在用Swing编写Java GUI程序。界面如下所示：

program

当用户点击右侧的其中一张图片时，我希望它的小预览显示在左上角的橙色区域中。我通过SwingWorker thread从计算机上的目录中提取所有图像文件。在SwingWorker的done() method中，我为每个对象添加了一个mouseClicked侦听器（来自我创建的类的TaggableImage对象。它有一个BufferedImage并扩展了JComponent，覆盖了paintComponent()方法）。在mouseClicked监听器中，我调用橙色面板的add（）方法并将其传递给TaggableImage。

我的问题：

当我点击其中一个图像时，它不会被添加到橙色面板，它会从右侧的面板中消失。如果我点击所有图像，我将留下一个空白的右侧面板。为什么会这样？

这是我的整个SwingWorker主题：

SwingWorker<ArrayList<TaggableImage>, Void> loadImagesAsyncWorker = new SwingWorker<ArrayList<TaggableImage>, Void>() {

    ArrayList<TaggableImage> img_list = new ArrayList<TaggableImage>();

    @Override
    protected ArrayList<TaggableImage> 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);
    }
}

Answer 1

考虑使用JList右侧面板来利用灵活的布局选项和选择处理，如here及以下所示。

enter image description here

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();
        });
    }
}

调用mouseClicked（）后JComponents消失

我的问题：

1 个答案: