如何在Android中使用okhttp暂停/继续下载

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现问题.

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是10MB.下载3MB然后恢复下载时暂停,下载完成后文件大小变成13MB.它不是从恢复时的下载大小开始,它从字节流开始下载.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,最后用BufferedSource解决了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);   
}

它运作成功.我想我很幸运:)

第二种方式

我为跳过下载的字节添加了标题,它工作正常.

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);   
}