How do I use JProgressBar to display file copy progress?

Question

我正在开发一个通过网络传输文件的项目，我想要合并一个JProgressBar来显示文件传输过程中的进度，但我需要帮助。

Answer 1

You probably would find a ProgressMonitorInputStream easiest, but if that doesn't do enough for you, look at its source code to get exactly what you want.

 InputStream in = new BufferedInputStream(
                     new ProgressMonitorInputStream(
                              parentComponent,
                              "Reading " + fileName,
                              new FileInputStream(fileName)
                     )
                  );

To use a different transfer method then substitute an appropriate stream for FileInputStream.

Answer 2

It sounds like you should be using a SwingWorker , as described in this Core Java Tech Tip . See also Using a Swing Worker Thread .

Answer 3

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import javax.swing.JProgressBar;

....

public OutputStream loadFile(URL remoteFile, JProgressBar progress) throws IOException
{
    URLConnection connection = remoteFile.openConnection(); //connect to remote file
    InputStream inputStream = connection.getInputStream(); //get stream to read file

    int length = connection.getContentLength(); //find out how long the file is, any good webserver should provide this info
    int current = 0;

    progress.setMaximum(length); //we're going to get this many bytes
    progress.setValue(0); //we've gotten 0 bytes so far

    ByteArrayOutputStream out = new ByteArrayOutputStream(); //create our output steam to build the file here

    byte[] buffer = new byte[1024];
    int bytesRead = 0;

    while((bytesRead = inputStream.read(buffer)) != -1) //keep filling the buffer until we get to the end of the file 
    {   
        out.write(buffer, current, bytesRead); //write the buffer to the file offset = current, length = bytesRead
        current += bytesRead; //we've progressed a little so update current
        progress.setValue(current); //tell progress how far we are
    }
    inputStream.close(); //close our stream

    return out;
}

I'm pretty sure this will work.

Answer 4

那么这里是JProgressBar的教程，也许这会有所帮助。