Question

我正在从客户端向服务器传输文件。我不知道转移所需的时间。但是我的UI将简单地保持不变，而不会对用户有任何暗示。我需要保持一个进度条，它应该是进展直到文件上传。我怎么能实现这个目标。

我在.net中了解这种情况。但我们怎么能在java中做到这一点？

Answer 1

对于真正“不确定”的行为，

trashgod's回答是正确的。为什么您认为您的文件传输适合此类别？你有没有在互联网上下载一个与之相关的进度条？你能想象不那个吗？

请参阅How do I use JProgressBar to display file copy progress?

的答案中提供的以下示例

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;
}

Answer 2

如How to Use Progress Bars所示，您可以指定 indeterminate mode ，直到您有足够的数据来衡量进度或下载结束。确切的实现取决于转移的发生方式。理想情况下，发送方首先提供长度，但也可以在数据累积时动态计算速率。

进度条时间计算+ java

2 个答案: