是否可以检查URLconnection.getInputStream（）的进度？ [英] Is it possible to check progress of URLconnection.getInputStream()?

问题描述

我想通过URLconnection检查下载文件的进度。是否可以或应该使用其他库？这是我的urlconnection函数：

I want to check progress of downloading file by URLconnection. Is it possible or should I use another library? This is my urlconnection function:

public static String sendPostRequest(String httpURL, String data) throws UnsupportedEncodingException, MalformedURLException, IOException {
    URL url = new URL(httpURL);

    URLConnection conn = url.openConnection();
    //conn.addRequestProperty("Content-Type", "text/html; charset=iso-8859-2");
    conn.setDoOutput(true);
    OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
    wr.write(data);
    wr.flush();

    BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream(), "ISO-8859-2"));
    String line, all = "";
    while ((line = rd.readLine()) != null) {
        all = all + line;
    }
    wr.close();
    rd.close();
    return all;
}

我知道整个文件都是在这行（或worng）下载的？：

I understand that whole file is downloaded in this line (or worng)?:

BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream(), "ISO-8859-2"));

那么可以在此代码中执行此操作吗？

So is it possible to do this in this code?

推荐答案

只需检查响应中是否存在HTTP Content-Length 标头。

Just check if the HTTP Content-Length header is present in the response.

int contentLength = connection.getContentLength();

if (contentLength != -1) {
    // Just do (readBytes / contentLength) * 100 to calculate the percentage.
} else {
    // You're lost. Show "Progress: unknown"
}

---

更新根据您的更新，您在 BufferedReader 中包装 InputStream 并且在循环中读取。您可以按如下方式计算字节数：

---

Update as per your update, you're wrapping the InputStream inside a BufferedReader and reading inside a while loop. You can count the bytes as follows:

int readBytes = 0;

while ((line = rd.readLine()) != null) {
    readBytes += line.getBytes("ISO-8859-2").length + 2; // CRLF bytes!!
    // Do something with line.
}

+ 2 是覆盖CRLF（回车和换行）字节，由 BufferedReader＃readLine（）吃掉。更简洁的方法是通过 InputStream #read（buffer）读取它，这样你就不需要按字符向前和向后按字节来计算读取的字节数。

The + 2 is to cover the CRLF (carriage return and linefeed) bytes which are eaten by BufferedReader#readLine(). More clean approach would be to just read it by InputStream#read(buffer) so that you don't need to massage the bytes forth and back from characters to calculate the read bytes.

• 如何使用 java.net.URLConnection 触发和处理HTTP请求？

• How to use java.net.URLConnection to fire and handle HTTP requests?

这篇关于是否可以检查URLconnection.getInputStream（）的进度？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！