java - 如何使用ProgressMonitorInputStream

我知道我肯定会遗漏一些非常明显的东西，但是每当我在复制文件时尝试使用ProgressMonitorInputStream时，都不会出现ProgressDialog弹出窗口。

我看到的示例除了将其输入流包装在ProgressMonitorInputStream中外似乎没有做其他事情。

文档说:

这将创建一个进度监视器，以监视读取输入流的进度。如果需要一些时间，将弹出一个ProgressDialog通知用户。如果用户单击“取消”按钮，则下次读取时将引发InterruptedIOException。关闭流后，便会执行所有正确的清除操作。

这是我放在一起的一个非常简单的示例，即使将setMillisToPopup()设置为一个非常小的数字，也永远不会弹出带有大文件的对话框。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingWorker;

public class ProgressBarDemo extends JFrame {

   private static final long serialVersionUID = 1L;

   private JButton button;

   ProgressBarDemo()
   {
      button = new JButton("Click me!");
      ButtonActionListener bal = new ButtonActionListener();
      button.addActionListener(bal);

      this.getContentPane().add(button);
   }

   private class ButtonActionListener implements ActionListener
   {

      @Override
      public void actionPerformed(ActionEvent e) {
         // TODO Auto-generated method stub
         Worker worker = new Worker();
         worker.execute();
         button.setEnabled(false);
      }
   }

   public void go() {

      this.setLocationRelativeTo(null);
      this.setVisible(true);
      this.pack();
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   }

   private class Worker extends SwingWorker<Void, Void>
   {

      private void copyFile() {

         File file = new File("/Users/mypath/Desktop/WirelessDiagnostics.tar.gz");

         BufferedInputStream bis;
         BufferedOutputStream baos;
         try {
            bis = new BufferedInputStream(new FileInputStream(file));
            ProgressMonitorInputStream pmis = new ProgressMonitorInputStream(
                  ProgressBarDemo.this,
                  "Reading... " + file.getAbsolutePath(),
                  bis);

            pmis.getProgressMonitor().setMillisToPopup(10);
            baos = new BufferedOutputStream(new FileOutputStream("/Users/mypath/Desktop/NewWirelessDiagnostics.tar.gz"));

            byte[] buffer = new byte[2048];
            int nRead = 0;

            while((nRead = pmis.read(buffer)) != -1) {
               baos.write(buffer, 0, nRead);
            }

            pmis.close();
            baos.flush();
            baos.close();
         } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
      }

      @Override
      protected Void doInBackground() throws Exception {
         // TODO Auto-generated method stub
         copyFile();
         return null;
      }

      @Override
      protected void done() {
         button.setEnabled(true);
      }
   }
}

public class TestProj {

   public static void main(String[] args) {
      ProgressBarDemo demo = new ProgressBarDemo();
      demo.go();
   }
}

有什么建议？

最佳答案

您正在事件调度线程的上下文中调用copyFile，这意味着EDT在方法返回之前无法响应新事件或绘制请求。

尝试将呼叫放在自己的Thread上下文中...

Thread t = new Thread(new Runnable(
    public void run() {
        copyFile();
    }
));
t.start();

同样，您可以使用SwingWorker，这有点过大了，但是您可以从PropertyChangeListener或done方法中受益，如果您想防止人们在按下按钮的同时点击该按钮，可以重新启用JButton复制操作正在进行中

有关更多详细信息，请参见Concurrency in Swing和Worker Threads and SwingWorker。

更新为示例

在本地磁盘上复制一个371mb的文件...

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingWorker;

public class ProgressBarDemo extends JFrame {

    private static final long serialVersionUID = 1L;

    private JButton button;

    ProgressBarDemo() {
        button = new JButton("Click me!");
        ButtonActionListener bal = new ButtonActionListener();
        button.addActionListener(bal);

        this.getContentPane().add(button);
    }

    public void go() {

        this.setLocationRelativeTo(null);
        this.setVisible(true);
        this.pack();
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    private void copyFile() {

        File file = new File("...");

        BufferedInputStream bis;
        BufferedOutputStream baos;
        try {
            bis = new BufferedInputStream(new FileInputStream(file));
            ProgressMonitorInputStream pmis = new ProgressMonitorInputStream(
                            this,
                            "Reading... " + file.getAbsolutePath(),
                            bis);

            pmis.getProgressMonitor().setMillisToPopup(10);
            baos = new BufferedOutputStream(new FileOutputStream("..."));

            byte[] buffer = new byte[2048];
            int nRead = 0;

            while ((nRead = pmis.read(buffer)) != -1) {
                baos.write(buffer, 0, nRead);
            }

            pmis.close();
            baos.flush();
            baos.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private class ButtonActionListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {

            button.setEnabled(false);
            SwingWorker worker = new SwingWorker() {

                @Override
                protected Object doInBackground() throws Exception {
                    copyFile();
                    return null;
                }

                @Override
                protected void done() {
                    button.setEnabled(true);
                }

            };

            worker.execute();
        }

    }

    public static void main(String[] args) {
        ProgressBarDemo demo = new ProgressBarDemo();
        demo.go();
    }
}

请记住，设置窗口和显示会涉及一些开销，这需要考虑在内。系统可能会“想”显示一个窗口，但是当系统设置好并准备显示它时， Steam可能已完成复制...

扩展示例

nb:我不太喜欢ProgressMonitor API，因为我无法找到UI与EDT同步的地方，这可能会导致Java 7和8出现问题

例如，您可以将这个想法正式化为一个独立的工作者。

public class CopyWorker extends SwingWorker {

    private File source;
    private File dest;
    private Component parent;

    private ProgressMonitorInputStream pmis;

    public CopyWorker(Component parent, File source, File dest) {
        this.parent = parent;
        this.source = source;
        this.dest = dest;
    }

    @Override
    protected Object doInBackground() throws Exception {
        try (InputStream is = new FileInputStream(source)) {
            try (OutputStream os = new FileOutputStream(dest)) {
                pmis = new ProgressMonitorInputStream(
                        parent,
                        "Copying...",
                        is);

                pmis.getProgressMonitor().setMillisToPopup(10);

                byte[] buffer = new byte[2048];
                int nRead = 0;

                while ((nRead = pmis.read(buffer)) != -1) {
                    os.write(buffer, 0, nRead);
                }
            }
        }
        return null;
    }

    @Override
    protected void done() {
        try {
            pmis.close();
        } catch (Exception e) {
        }
    }

}

这试图包含功能，但也要处理ProgressMonitorInputStream方法中的done，以确保它在EDT中完成。我个人会附加一个PropertyChangeListener并监视done属性，以确定工作人员何时完成并检查返回结果以获取任何异常，这使您能够以自己的方式处理异常并取消使您的过程中的工人