ProgressMonitorInputStream

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();

    }

}