假设我有一个带有以下代码的JList：
final JList<String> list = new JList<String>(model);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.setToolTipText("Choose Version");
list.setBounds(10, 150, 414, 23);
我想提供一种功能，用户可以从该JList上选择一个文件，该文件托管在网站上，然后下载。对于JList名称，我将使用托管文件的名称。 （我想通过使用JSoup来做到这一点）
到目前为止，我有以下代码来显示名称：
DefaultListModel<String> model = new DefaultListModel<String>();
Document doc = null;
try {
doc = Jsoup.connect("https://mega.nz/fm/rqwQRKyR").get();
} catch (IOException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
for (Element file : doc.select("td.right td a")) {
model.addElement(file.attr("href"));
}
在此示例代码中，我从网站获得文件名，并将文件名添加到DefaultListModel。然后，使用此模型创建一个新的JList。
但是，我如何使我的程序能够使用JSoup下载基于文件名选择的特定文件？
嗯，在阅读了有关如何使用JSoup下载图像的this问答之后，我得到了下面的代码。在您未指定要仅将图像下载到内存中还是将其保存在本地文件时，我实现了代码，使两者都可以（即先下载，然后提示用户将其保存）。他/她想要的）。
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.Window;
import java.awt.image.BufferedImage;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.util.Objects;
import javax.imageio.ImageIO;
import javax.swing.DefaultListModel;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import org.jsoup.Jsoup;
public class Main {
//A JDialog which allows the user to save the downloaded image locally...
private static class ImageDialog extends JDialog {
private final BufferedImage bimg;
private ImageDialog(final Window owner,
final String title,
final JFileChooser sharedChooser,
final BufferedImage bimg) {
super(owner, title, ModalityType.APPLICATION_MODAL);
this.bimg = Objects.requireNonNull(bimg);
final JLabel label = new JLabel(new ImageIcon(bimg), JLabel.CENTER);
final JScrollPane scroll = new JScrollPane(label);
scroll.setPreferredSize(new Dimension(600, 600));
final JList<String> options = new JList<>(ImageIO.getWriterFormatNames());
options.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
final JButton save = new JButton("Save");
save.addActionListener(e -> {
if (JOptionPane.OK_OPTION == JOptionPane.showConfirmDialog(ImageDialog.this, options, "Select image type", JOptionPane.OK_CANCEL_OPTION)) {
final String imageFormat = options.getSelectedValue();
if (imageFormat == null)
JOptionPane.showMessageDialog(ImageDialog.this, "You have to select an image type first!");
else if (sharedChooser.showSaveDialog(ImageDialog.this) == JFileChooser.APPROVE_OPTION) {
final File imagePath = sharedChooser.getSelectedFile();
if (imagePath.exists()) //I would avoid overwriting files.
JOptionPane.showMessageDialog(ImageDialog.this, "You cannot overwrite images! Delete them manually first.", "Oups!", JOptionPane.WARNING_MESSAGE);
else {
try {
ImageIO.write(bimg, imageFormat, imagePath);
JOptionPane.showMessageDialog(ImageDialog.this, "Saved image successfully under \"" + imagePath + "\".", "Ok", JOptionPane.INFORMATION_MESSAGE);
}
catch (final IOException iox) {
iox.printStackTrace();
JOptionPane.showMessageDialog(ImageDialog.this, "Failed to save image! " + iox, "Error!", JOptionPane.ERROR_MESSAGE);
}
}
}
}
});
final JPanel contents = new JPanel(new BorderLayout());
contents.add(scroll, BorderLayout.CENTER);
contents.add(save, BorderLayout.PAGE_END);
super.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
super.getContentPane().add(contents);
super.pack();
super.setLocationRelativeTo(owner);
}
}
public static void main(final String[] args) {
//This is where you fill the model:
final DefaultListModel<String> model = new DefaultListModel<>();
model.addElement("https://i.stack.imgur.com/PUMHY.png");
model.addElement("https://i.stack.imgur.com/PUMHY.png");
model.addElement("https://i.stack.imgur.com/PUMHY.png");
model.addElement("https://i.stack.imgur.com/PUMHY.png");
//List creation and initialization:
final JList<String> list = new JList<>(model);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
//JScrollPane for list:
final JScrollPane scroll = new JScrollPane(list);
scroll.setPreferredSize(new Dimension(400, 400));
final JFileChooser sharedChooser = new JFileChooser();
sharedChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
sharedChooser.setMultiSelectionEnabled(false);
final JProgressBar bar = new JProgressBar();
bar.setBorderPainted(false);
bar.setStringPainted(true);
bar.setString("Downloading, please wait...");
bar.setIndeterminate(true);
//Create an extra panel which will have the progress bar centered in it...
final JPanel centeredBar = new JPanel(new GridBagLayout());
centeredBar.add(bar);
final JButton button = new JButton("Download");
final JPanel contents = new JPanel(new BorderLayout());
contents.add(scroll, BorderLayout.CENTER);
contents.add(button, BorderLayout.PAGE_END);
//Creating the cards to add in the content pane of the jframe:
final String cardProgressBar = "PROGRESS_BAR",
cardList = "LIST";
final CardLayout cardl = new CardLayout();
final JPanel cards = new JPanel(cardl);
cards.add(contents, cardList);
cards.add(centeredBar, cardProgressBar);
cardl.show(cards, cardList);
final JFrame frame = new JFrame("JList for JSoup");
button.addActionListener(e -> {
cardl.show(cards, cardProgressBar);
new Thread(() -> {
final String imagePath = list.getSelectedValue();
if (imagePath == null)
JOptionPane.showMessageDialog(frame, "No image selected!");
else {
try {
//This is the actual downloading you requested:
try (final BufferedInputStream bis = Jsoup.connect(imagePath).ignoreContentType(true).execute().bodyStream()) {
final BufferedImage bimg = ImageIO.read(bis);
new ImageDialog(frame, imagePath, sharedChooser, bimg).setVisible(true);
}
}
catch (final IOException iox) {
iox.printStackTrace();
JOptionPane.showMessageDialog(frame, "Failed to download \"" + imagePath + "\"! " + iox);
}
finally {
cardl.show(cards, cardList);
}
}
}).start();
});
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(cards);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
您必须使用自己的代码显示方式来填充列表模型。在上面的示例代码中，我多次用一些随机值填充它。
您还可以将调用Jsoup.connect(imagePath).ignoreContentType(true).execute().bodyStream()替换为Jsoup.connect(imagePath).ignoreContentType(true).execute().bodyAsBytes()，这将允许最大2GB的文件（因为我想您不能在Java中分配大于Integer.MAX_VALUE的字节数组）。让我知道这是否是您想要的。