Swing类包中有一个很有用的流过滤器，ProgressMonitorInputStream，它可以自动弹出一个对话框，监视已经读取了多少流。
进度监视器流使用InputStream类的available方法来确定流中的总字节数。不过available方法只报告流中可访问的、未中断的字节数。
进度监视器适用于文件以及HTTP URL,因为它们的长度都是事先可知道的，但它不适用于所有的流。
package swing.progress; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.util.Scanner; import javax.swing.JFileChooser; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JScrollPane; import javax.swing.JTextArea; import javax.swing.ProgressMonitorInputStream; import javax.swing.SwingUtilities; import javax.swing.SwingWorker; /*2015-7-6*/ public class ProgressMonitorInputStreamTest { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame frame = new TextFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); frame.setLocationRelativeTo(null); } }); } } class TextFrame extends JFrame { private static final long serialVersionUID = 1L; private JMenuItem openItem; private JMenuItem exitItem; private JTextArea textArea; private JFileChooser chooser; public static final int DEFAULT_WIDTH = 300; public static final int DEFAULT_HEIGHT = 200; public TextFrame() { setTitle("ProgressMonitorInputStreamTest"); setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); textArea = new JTextArea(); add(new JScrollPane(textArea)); chooser = new JFileChooser(); chooser.setCurrentDirectory(new File(".")); JMenuBar menuBar = new JMenuBar(); setJMenuBar(menuBar); JMenu fileMenu = new JMenu("File"); menuBar.add(fileMenu); openItem = new JMenuItem("Open"); openItem.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { try { openFile(); } catch (FileNotFoundException e1) { e1.printStackTrace(); } } }); fileMenu.add(openItem); exitItem = new JMenuItem("Exit"); exitItem.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.exit(0); } }); fileMenu.add(exitItem); } protected void openFile() throws FileNotFoundException { int r = chooser.showOpenDialog(this); if (r != JFileChooser.APPROVE_OPTION) { return; } File f = chooser.getSelectedFile(); FileInputStream fileIn = new FileInputStream(f); ProgressMonitorInputStream progressIn = new ProgressMonitorInputStream(this, "Reading " + f.getName(), fileIn); final Scanner in = new Scanner(progressIn); textArea.setText(""); SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() { @Override protected Void doInBackground() throws Exception { while (in.hasNextLine()) { String line = in.nextLine(); textArea.append(line); textArea.append("\n"); } in.close(); return null; } }; worker.execute(); } }
