java编写的文件下载管理器Manager代码

import java.awt.BorderLayout; import java.awt.Component; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.util.ArrayList; import java.util.Observable; import java.util.Observer; import javax.swing.BorderFactory; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JProgressBar; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.JTextField; import javax.swing.ListSelectionModel; import javax.swing.event.ListSelectionEvent; import javax.swing.event.ListSelectionListener; import javax.swing.table.AbstractTableModel; import javax.swing.table.TableCellRenderer; public class DownloadManager extends JFrame implements Observer { private JTextField addTextField = new JTextField(30); private DownloadsTableModel tableModel = new DownloadsTableModel(); private JTable table; private JButton pauseButton = new JButton("Pause"); private JButton resumeButton = new JButton("Resume"); private JButton cancelButton, clearButton; private Download selectedDownload; private boolean clearing; public DownloadManager() { setTitle("Download Manager"); setSize(640, 480); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); 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) { System.exit(0); } }); fileMenu.add(fileExitMenuItem); menuBar.add(fileMenu); setJMenuBar(menuBar); // Set up add panel. JPanel addPanel = new JPanel(); 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. table = new JTable(tableModel); table.getSelectionModel().addListSelectionListener(new ListSelectionListener() { public void valueChanged(ListSelectionEvent e) { tableSelectionChanged(); } }); table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); ProgressRenderer renderer = new ProgressRenderer(0, 100); renderer.setStringPainted(true); // show progress text table.setDefaultRenderer(JProgressBar.class, renderer); table.setRowHeight((int) renderer.getPreferredSize().getHeight()); JPanel downloadsPanel = new JPanel(); downloadsPanel.setBorder(BorderFactory.createTitledBorder("Downloads")); downloadsPanel.setLayout(new BorderLayout()); downloadsPanel.add(new JScrollPane(table), BorderLayout.CENTER); JPanel buttonsPanel = new JPanel(); pauseButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { actionPause(); } }); pauseButton.setEnabled(false); buttonsPanel.add(pauseButton); 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); getContentPane().setLayout(new BorderLayout()); getContentPane().add(addPanel, BorderLayout.NORTH); getContentPane().add(downloadsPanel, BorderLayout.CENTER); getContentPane().add(buttonsPanel, BorderLayout.SOUTH); } 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); } } private URL verifyUrl(String url) { if (!url.toLowerCase().startsWith("http://")) return null; URL verifiedUrl = null; try { verifiedUrl = new URL(url); } catch (Exception e) { return null; } if (verifiedUrl.getFile().length() < 2) return null; return verifiedUrl; } private void tableSelectionChanged() { if (selectedDownload != null) selectedDownload.deleteObserver(DownloadManager.this); if (!clearing && table.getSelectedRow() > -1) { selectedDownload = tableModel.getDownload(table.getSelectedRow()); selectedDownload.addObserver(DownloadManager.this); updateButtons(); } } private void actionPause() { selectedDownload.pause(); updateButtons(); } private void actionResume() { selectedDownload.resume(); updateButtons(); } private void actionCancel() { selectedDownload.cancel(); updateButtons(); } private void actionClear() { clearing = true; tableModel.clearDownload(table.getSelectedRow()); clearing = false; selectedDownload = null; updateButtons(); } 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 { pauseButton.setEnabled(false); resumeButton.setEnabled(false); cancelButton.setEnabled(false); clearButton.setEnabled(false); } } public void update(Observable o, Object arg) { // Update buttons if the selected download has changed. if (selectedDownload != null && selectedDownload.equals(o)) updateButtons(); } // Run the Download Manager. public static void main(String[] args) { DownloadManager manager = new DownloadManager(); manager.setVisible(true); } } class Download extends Observable implements Runnable { private static final int MAX_BUFFER_SIZE = 1024; public static final String STATUSES[] = { "Downloading", "Paused", "Complete", "Cancelled", "Error" }; public static final int DOWNLOADING = 0; publi