如何 pause/resume 在 Android 中使用 okhttp 下载

Question

我在 android 中使用 okhttp 库下载文件。我下载成功了。但是当我暂停并恢复下载时出了点问题。

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

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

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

long totalByteSize = responseBody.contentLength();
byte[] data = new byte[1024];
int count = 0;

while ((count = input.read(data)) != -1) {
    downloadedSize += count;
    output.write(data, 0, count);   
}

问题是例如文件大小为 10MB。下载 3MB 时我暂停，然后继续下载，下载完成后文件大小变为 13MB。它不是从恢复时的下载大小开始，而是从字节流的开头开始下载。所以文件变成13MB。代码有什么问题？

Answer 1

第一种方式

我尝试了很多代码，最后我用 BufferedSource source = responseBody.source(); 解决了； source.skip(下载大小);

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);   
}

它运行成功。我觉得我很幸运:)

第二种方式

我添加了 header 以跳过下载的字节，它起作用了。

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);   
}

Answer 2

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()

根据您的请求恢复使用 "Range" header 并将流附加到已下载的文件。

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