val call = client.newCall(request)

call.enqueue(object : Callback {
    override fun onFailure(call: Call, e: IOException) {
        listener.onFail(e)
    }

    override fun onResponse(call: Call, response: Response) {
        // write the stream to a file (downloading happening)
        val stream = response.body?.byteStream()
    }
})

// this will stop the downloading
call.cancel()

恢复使用“范围”头与您的请求和附加流已经下载的文件.

根据 Alexandria 回答，我已经尝试了他推荐的两种方法。第一种方法在下载停止时产生错误，然后在应用程序重新启动后继续。我发现第二种方法更稳定。代码中还有一个语法错误。示例代码在这里。

File file = new File(path);
        long availableFileLength = file.exists() && file.isFile() ? file.length() :0;
        Request.Builder requestBuilder = new Request.Builder();
        requestBuilder.addHeader("Range", "bytes=" + String.valueOf(availableFileLength) + "-");
        Request request = requestBuilder.url(url).build();
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
            .readTimeout(30, TimeUnit.SECONDS)
            .connectTimeout(30, TimeUnit.SECONDS)
            .build();
        ResponseBody responseBody = okHttpClient.newCall(request).execute().body();

        InputStream input = new BufferedInputStream(responseBody.byteStream());
        OutputStream output = new FileOutputStream(downloadPath, true);

        long currentDownloadedSize = 0;
        long currentTotalByteSize = responseBody.contentLength();
        byte[] data = new byte[1024];
        int count = 0;
        while ((count = input.read(data)) != -1) {
             currentDownloadedSize += count;
             output.write(data, 0, count);   
        }

第一种方式

我试了很多代码，最后用BufferedSource source = responseBody.source（）; source.skip（downloadedSize）;

Response request = new Request.Builder().url(url).build();
ResponseBody responseBody = response.body();
BufferedSource source = responseBody.source();

if(isResume)
    source.skip(downloadedSize);

File file = new File(filePath);
BufferedInputStream input = new BufferedInputStream(responseBody.byteStream());
OutputStream output;

if (isResume) {
    output = new FileOutputStream(file, true);
} else {
    output = new FileOutputStream(file, false);    
}

long currentDownloadedSize = 0;
long currentTotalByteSize = responseBody.contentLength();
byte[] data = new byte[1024];
int count = 0;
while ((count = input.read(data)) != -1) {
    currentDownloadedSize += count;
    output.write(data, 0, count);   
}

成功了。我觉得我很幸运：）

第二条路

我添加了跳过下载字节的头，它的工作。

Request.Builder requestBuilder = new Request.Builder();
if (isResume) {
    requestBuilder.addHeader("Range", "bytes=" + String.valueOf(downloadedSize) + "-");
}
Response request = requestBuilder.url(url).build();
ResponseBody responseBody = response.body();
BufferedSource source = responseBody.source();

File file = new File(filePath);
BufferedInputStream input = new BufferedInputStream(responseBody.byteStream());
OutputStream output;

if (isResume) {
    output = new FileOutputStream(file, true);
} else {
    output = new FileOutputStream(file, false);    
}

long currentDownloadedSize = 0;
long currentTotalByteSize = responseBody.contentLength();
byte[] data = new byte[1024];
int count = 0;
while ((count = input.read(data)) != -1) {
    currentDownloadedSize += count;
    output.write(data, 0, count);   
}