如何使用ProgressMonitorInputStream

Question

我知道我必须遗漏一些非常明显的东西,但每当我在复制文件时尝试使用ProgressMonitorInputStream时,我都不会得到ProgressDialog弹出窗口.

我看到的示例除了将它们的输入流包装在ProgressMonitorInputStream中之外似乎没什么用处.

文档说:

这将创建一个进度监视器来监视读取输入流的进度.如果需要一段时间,将弹出ProgressDialog以通知用户.如果用户点击取消按钮,则下次读取时将抛出InterruptedIOException.在关闭流时完成所有正确的清理.

这是一个非常简单的例子,我把它放在一起,永远不会弹出带有大文件的对话框,即使我setMillisToPopup()是一个非常小的数字.

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？

Answer 1

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

尝试将呼叫置于其自己的Thread上下文中......

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

同样,你可以使用SwingWorker,这是矫枉过正的一点点,但你得到的利益PropertyChangeListener或它的done方法,它可以用来重新启用JButton,你应该想阻止人们点击按钮同时复制操作进行中

有关更多详细信息,请参阅Swing和工作线程中的并发和SwingWorker

更新了示例

在本地磁盘上复制371mb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,设置窗口和显示需要花费开销,这需要考虑因素.系统可能"想要"显示窗口,但是当系统设置好并准备显示它时,蒸汽可能已完成复制......

扩展示例

nb:我不太喜欢ProgressMonitorAPI,因为我无法找到UI与EDT同步的位置,这可能会导致Java 7和8中出现问题

你可以将这个想法形式化为一个自给自足的工人,例如......

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,但也处理方法ProgressMonitorInputStream内部的清理done,确保它在EDT内完成.我个人会附上一个PropertyChangeListener并监控该done属性,以确定工人何时完成并检查返回结果以便获取任何异常,这使您能够以自己的方式处理异常并将其分离.你的过程中的工人