Android部分下载的文件报告文件大小错误 [英] Android Partially Downloaded Files Report Wrong File Size

问题描述

我正在整理一些代码以从Android中的HTTP地址下载文件。如果下载在途中失败，我想支持恢复下载。

I'm putting together some code to download files from an HTTP address in Android. I'd like to support download resumption if the download fails mid way.

开始下载时获得的输出，然后终止wifi连接并再次重新启动几次：以下内容：

The output I get when starting the download, then killing the wifi connection and restarting again several times is the following:

开始大小0
停止大小12333416
开始大小12333416
停止大小 16058200
开始大小 3724784

我不明白为什么在第一次恢复后，部分下载的文件的后续文件大小读数不匹配。

I cannot understand why after the first resumption, subsequent file size readings of the partially downloaded file do not match.

预先感谢！

public void download(String source, String target) throws IOException {
    BufferedOutputStream outputStream = null;
    InputStream inputStream = null;

    try {
        File targetFile = new File(target);
        currentBytes = targetFile.length();

        Log.i(TAG, "Start size " + String.valueOf(currentBytes));
        outputStream = new BufferedOutputStream(new FileOutputStream(targetFile));

        // create the input stream
        URLConnection connection = (new URL(source)).openConnection();
        connection.setConnectTimeout(mCoTimeout);
        connection.setReadTimeout(mSoTimeout);

        inputStream = connection.getInputStream();
        inputStream.skip(currentBytes);

        // calculate the total bytes
        totalBytes = connection.getContentLength();

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

        while ((bytesRead = inputStream.read(buffer)) > 0) {
            // write the bytes to file
            outputStream.write(buffer, 0, bytesRead);
            outputStream.flush();

            currentBytes += bytesRead;
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (outputStream != null) {
            // close the output stream
            outputStream.flush();
            outputStream.close();
        }

        if (inputStream != null) {
            // close the input stream
            inputStream.close();
        }

        Log.i(TAG, "Stop size " + String.valueOf(currentBytes));
    }
}

推荐答案

有您做错了两件事：

1. 要恢复下载到文件，您应该附加文件而不是重写文件。对输出流使用特殊的构造函数：

1. To resume download to file you should append, not rewrite the file. Use special constructor for output stream:

FileOutputStream（targetFile，true）

FileOutputStream(targetFile, true)

请求部分内容服务器上的文件，您应该使用HTTP 1.1属性 Range。您可以这样操作：

To request part of file from server you should use HTTP 1.1 property "Range". You can do it like this:

HttpURLConnection httpConnection =（HttpURLConnection）连接；
connection.setRequestProperty（ Range， bytes = + currentBytes +-）;

HttpURLConnection httpConnection = (HttpURLConnection) connection; connection.setRequestProperty("Range", "bytes=" + currentBytes + "-");

这篇关于Android部分下载的文件报告文件大小错误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！