使用Java创建的下载管理器.rar_download manager_java swing_断点续传

import java.awt.*; import java.awt.event.*; import java.net.*; import java.util.*; import javax.swing.*; import javax.swing.event.*; // The Download Manager. public class DownloadManager extends JFrame implements Observer { // Add download text field. private JTextField addTextField; // Download table's data model. private DownloadsTableModel tableModel; // Table listing downloads. private JTable table; // These are the buttons for managing the selected download. private JButton pauseButton, resumeButton; private JButton cancelButton, clearButton; // Currently selected download. private Download selectedDownload; // Flag for whether or not table selection is being cleared. private boolean clearing; // Constructor for Download Manager. public DownloadManager() { // Set application title. setTitle("Download Manager"); // Set window size. setSize(640, 480); // Handle window closing events. addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { actionExit(); } }); // Set up file menu. JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); fileMenu.setMnemonic(KeyEvent.VK_F); JMenuItem fileExitMenuItem = new JMenuItem("Exit", KeyEvent.VK_X); fileExitMenuItem.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionExit(); } }); fileMenu.add(fileExitMenuItem); menuBar.add(fileMenu); setJMenuBar(menuBar); // Set up add panel. JPanel addPanel = new JPanel(); addTextField = new JTextField(30); addPanel.add(addTextField); JButton addButton = new JButton("Add Download"); addButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionAdd(); } }); addPanel.add(addButton); // Set up Downloads table. tableModel = new DownloadsTableModel(); table = new JTable(tableModel); table.getSelectionModel().addListSelectionListener(new ListSelectionListener() { public void valueChanged(ListSelectionEvent e) { tableSelectionChanged(); } }); // Allow only one row at a time to be selected. table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); // Set up ProgressBar as renderer for progress column. ProgressRenderer renderer = new ProgressRenderer(0, 100); renderer.setStringPainted(true); // show progress text table.setDefaultRenderer(JProgressBar.class, renderer); // Set table's row height large enough to fit JProgressBar. table.setRowHeight( (int) renderer.getPreferredSize().getHeight()); // Set up downloads panel. JPanel downloadsPanel = new JPanel(); downloadsPanel.setBorder( BorderFactory.createTitledBorder("Downloads")); downloadsPanel.setLayout(new BorderLayout()); downloadsPanel.add(new JScrollPane(table), BorderLayout.CENTER); // Set up buttons panel. JPanel buttonsPanel = new JPanel(); pauseButton = new JButton("Pause"); pauseButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionPause(); } }); pauseButton.setEnabled(false); buttonsPanel.add(pauseButton); resumeButton = new JButton("Resume"); resumeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionResume(); } }); resumeButton.setEnabled(false); buttonsPanel.add(resumeButton); cancelButton = new JButton("Cancel"); cancelButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionCancel(); } }); cancelButton.setEnabled(false); buttonsPanel.add(cancelButton); clearButton = new JButton("Clear"); clearButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionClear(); } }); clearButton.setEnabled(false); buttonsPanel.add(clearButton); // Add panels to display. getContentPane().setLayout(new BorderLayout()); getContentPane().add(addPanel, BorderLayout.NORTH); getContentPane().add(downloadsPanel, BorderLayout.CENTER); getContentPane().add(buttonsPanel, BorderLayout.SOUTH); } // Exit this program. private void actionExit() { System.exit(0); } // Add a new download. private void actionAdd() { URL verifiedUrl = verifyUrl(addTextField.getText()); if (verifiedUrl != null) { tableModel.addDownload(new Download(verifiedUrl)); addTextField.setText(""); // reset add text field } else { JOptionPane.showMessageDialog(this, "Invalid Download URL", "Error", JOptionPane.ERROR_MESSAGE); } } // Verify download URL. private URL verifyUrl(String url) { // Only allow HTTP URLs. if (!url.toLowerCase().startsWith("http://")) return null; // Verify format of URL. URL verifiedUrl = null; try { verifiedUrl = new URL(url); } catch (Exception e) { return null; } // Make sure URL specifies a file. if (verifiedUrl.getFile().length() < 2) return null; return verifiedUrl; } // Called when table row selection changes. private void tableSelectionChanged() { /* Unregister from receiving notifications from the last selected download. */ if (selectedDownload != null) selectedDownload.deleteObserver(DownloadManager.this); /* If not in the middle of clearing a download, set the selected download and register to receive notifications from it. */ if (!clearing) { selectedDownload = tableModel.getDownload(table.getSelectedRow()); selectedDownload.addObserver(DownloadManager.this); updateButtons(); } } // Pause the selected download. private void actionPause() { selectedDownload.pause(); updateButtons(); } // Resume the selected download. private void actionResume() { selectedDownload.resume(); updateButtons(); } // Cancel the selected download. private void actionCancel() { selectedDownload.cancel(); updateButtons(); } // Clear the selected download. private void actionClear() { clearing = true; tableModel.clearDownload(table.getSelectedRow()); clearing = false; selectedDownload = null; updateButtons(); } /* Update each button's state based off of the currently selected download's status. */ private void updateButtons() { if (selectedDownload != null) { int status = selectedDownload.getStatus(); switch (status) { case Download.DOWNLOADING: pauseButton.setEnabled(true); resumeButton.setEnabled(false); cancelButton.setEnabled(true); clearButton.setEnabled(false); break; case Download.PAUSED: pauseButton.setEnabled(false); resumeButton.setEnabled(true); cancelButton.setEnabled(true); clearButton.setEnabled(false); break; case Download.ERROR: pauseButton.setEnabled(false); resumeButton.setEnabled(true); cancelButton.setEnabled(false); clearButton.setEnabled(true); break; default: // COMPLETE or CANCELLED pauseButton.setEnabled(false); resumeButton.setEnabled(false); cancelButton.setEnabled(false); clearButton.setEnabled(true); } } else { // No download is selected in table. pauseButton.setEnabled(false); resumeButton.setEnabled(false); canc