Retrofit2文件上传下载及其进度显示

一.文件上传
第一种方法

//接口
@Multipart
@POST("fileService")
Call uploadFile(@Part MultipartBody.Part file);

构造请求体上传

File file = new File(filePath);
RequestBody body = RequestBody.create(MediaType.parse("application/otcet-stream", file);
MultipartBody.Part part = MultipartBody.Part.createFormData("file", file.getName(), body);
Call call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);

第二种方法

//接口
@Multipart
@POST("fileService")
Call uploadFile(@Part("file\"; filename=\"image.png\"") RequestBody imgs);

构造请求体上传

File file = new File(filePath);
RequestBody body = RequestBody.create(MediaType.parse("multipart/form-data"), file);
Call call = getRetrofitService().uploadOneFile(body );
call.enqueue(callback);

知识点
"application/otcet-stream" ：八进制数据流的形式传输的。
"multipart/form-data" ： 以Form表单的形式上传文件。
"file"; filename="image.png"" ： file 为服务端接收文件的参数，此时文件名固定为image.png 。
("file", file.getName(), body) ：file 为服务端接收文件的参数，此时文件名为文件自身的名字。

这样就可以将这个文件上传到服务器，但Retrofit本身是不支持文件上传进度显示的，所以就需要我们自己扩展一个RequestBody来实现进度显示，实现完成之后只需要将上面body进行包装转换即可
上传进度显示

RetrofitCallback callback = new RetrofitCallback() {
  @Override
public void onSuccess(Call call, Response response) {
runOnUIThread(activity, response.body().toString());
//进度更新结束
}
@Override
public void onFailure(Call call, Throwable t) {
runOnUIThread(activity, t.getMessage());
//进度更新结束
}
@Override
public void onLoading(long total, long progress) {
super.onLoading(total, progress);
//此处进行进度更新
}
};
RequestBody body1 = RequestBody.create(MediaType.parse("application/otcet-stream"), file);
//通过该行代码将RequestBody转换成特定的FileRequestBody
FileRequestBody body = new FileRequestBody(body1, callback);
MultipartBody.Part part = MultipartBody.Part.createFormData("file", file.getName(), body);
Call call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);

回调RetrofitCallback

public abstract class RetrofitCallback implements Callback {
@Override
public void onResponse(Call call, Response response) {
if(response.isSuccessful()) {
onSuccess(call, response);
} else {
onFailure(call, new Throwable(response.message()));
}
}
public abstract void onSuccess(Call call, Response response);
public void onLoading(long total, long progress) {
}
}

FileRequestBody

/**
* 扩展OkHttp的请求体，实现上传时的进度提示
*
* @param 
*/
public final class FileRequestBody extends RequestBody {
/**
* 实际请求体
*/
private RequestBody requestBody;
/**
* 上传回调接口
*/
private RetrofitCallback callback;
/**
* 包装完成的BufferedSink
*/
private BufferedSink bufferedSink;
public FileRequestBody(RequestBody requestBody, RetrofitCallback callback) {
super();
this.requestBody = requestBody;
this.callback = callback;
}

@Override
public long contentLength() throws IOException {
return requestBody.contentLength();
}
@Override
public MediaType contentType() {
return requestBody.contentType();
}
@Override
public void writeTo(BufferedSink sink) throws IOException {
if (bufferedSink == null) {
//包装
bufferedSink = Okio.buffer(sink(sink));
}
//写入
requestBody.writeTo(bufferedSink);
//必须调用flush，否则最后一部分数据可能不会被写入
bufferedSink.flush();
}
/**
* 写入，回调进度接口
* @param sink Sink
* @return Sink
*/
private Sink sink(Sink sink) {
return new ForwardingSink(sink) {
//当前写入字节数
long bytesWritten = 0L;
//总字节长度，避免多次调用contentLength()方法
long contentLength = 0L;
@Override
public void write(Buffer source, long byteCount) throws IOException {
super.write(source, byteCount);
if (contentLength == 0) {
//获得contentLength的值，后续不再调用
contentLength = contentLength();
}
//增加当前写入的字节数
bytesWritten += byteCount;
//回调
callback.onLoading(contentLength, bytesWritten);
}
};
}
}

二.文件下载
接口定义
文件下载请求与普通的Get和Post请求是一样的，只是他们的返回值不一样而已，文件下载请求的返回值一般定义成ResponseBody

//这里只举例POST方式进行文件下载
@FormUrlEncoded
@POST("fileService")
Call downloadFile(@Field("param") String param);

发起请求

RetrofitCallback callback = new RetrofitCallback() {
@Override
public void onSuccess(Call call, Response response) {
try {
InputStream is = response.body().byteStream();
String path = Util.getSdCardPath();
File file = new File(path, "download.jpg");
FileOutputStream fos = new FileOutputStream(file);
BufferedInputStream bis = new BufferedInputStream(is);
byte[] buffer = new byte[1024];
int len;
while ((len = bis.read(buffer)) != -1) {
fos.write(buffer, 0, len);
}
fos.flush();
fos.close();
bis.close();
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void onFailure(Call call, Throwable t) {
runOnUIThread(activity, t.getMessage());
}
};

Call call = getRetrofitService(callback).downloadFile(param);
call.enqueue(callback);

下载进度显示
下载进度显示有两种方式实现，一种是通过OkHttp设置拦截器将ResponseBody进行转换成我们扩展后的ResponseBody，另外一种则是在上面的回调Callback中将ResponseBody的流写入到文件时进行进度处理，下面分别进行介绍。
1.扩展ResponseBody设置OkHttp拦截器

private  RetrofitService getRetrofitService(final RetrofitCallback callback) {
OkHttpClient.Builder clientBuilder = new OkHttpClient.Builder();
clientBuilder.addInterceptor(new Interceptor() {
@Override
public okhttp3.Response intercept(Chain chain) throws IOException {
okhttp3.Response response = chain.proceed(chain.request());
//将ResponseBody转换成我们需要的FileResponseBody
return response.newBuilder().body(new FileResponseBody(response.body(), callback)).build();
}
});
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(clientBuilder.build())
.addConverterFactory(GsonConverterFactory.create())
.build();
RetrofitService service = retrofit.create(RetrofitService.class);
return service ;
}

通过上面的设置后，我们需要在回调RetrofitCallback中实现onLoading方法来进行进度的更新操作，与上传文件的方法相同

FileResponseBody

/**
* 扩展OkHttp的请求体，实现上传时的进度提示
*
* @param 
*/
public final class FileResponseBody extends ResponseBody {
/**
* 实际请求体
*/
private ResponseBody mResponseBody;
/**
* 下载回调接口
*/
private RetrofitCallback mCallback;
/**
* BufferedSource
*/
private BufferedSource mBufferedSource;
public FileResponseBody(ResponseBody responseBody, RetrofitCallback callback) {
super();
this.mResponseBody = responseBody;
this.mCallback = callback;
}
@Override
public BufferedSource source() {
if (mBufferedSource == null) {
mBufferedSource = Okio.buffer(source(mResponseBody.source()));
}
return mBufferedSource;
}
@Override
public long contentLength() {
return mResponseBody.contentLength();
}
@Override
public MediaType contentType() {
return mResponseBody.contentType();
}
/**
* 回调进度接口
* @param source
* @return Source
*/
private Source source(Source source) {
return new ForwardingSource(source) {
long totalBytesRead = 0L;
@Override
public long read(Buffer sink, long byteCount) throws IOException {
long bytesRead = super.read(sink, byteCount);
totalBytesRead += bytesRead != -1 ? bytesRead : 0;
mCallback.onLoading(mResponseBody.contentLength(), totalBytesRead);
return bytesRead;
}
};
}
}

2.直接在回调中进行进度更新
上面介绍了通过扩展ResponseBody同时设置OkHttp拦截器来实现进度条更新显示，另外也可以直接在请求回调onSuccess中将流转换成文件时实现进度更新，下面给出大致实现

RetrofitCallback callback = new RetrofitCallback() {
@Override
public void onSuccess(Call call, Response response) {
try {
InputStream is = response.body().byteStream();
//获取文件总长度
long totalLength = is.available();

String path = Util.getSdCardPath();
File file = new File(path, "download.jpg");
FileOutputStream fos = new FileOutputStream(file);
BufferedInputStream bis = new BufferedInputStream(is);
byte[] buffer = new byte[1024];
int len;
while ((len = bis.read(buffer)) != -1) {
fos.write(buffer, 0, len);
//此处进行更新操作
//len即可理解为已下载的字节数
//onLoading(len, totalLength);
}
fos.flush();
fos.close();
bis.close();
is.close();
//此处就代表更新结束
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void onFailure(Call call, Throwable t) {
runOnUIThread(activity, t.getMessage());
}
};