Retrofit2文件上传下载及其进度显示

序

前面一篇文章介绍了Retrofit2的基本使用，这篇文章接着介绍使用Retrofit2实现文件上传和文件下载，以及上传下载过程中如何实现进度的显示。

文件上传

定义接口

@Multipart
@POST("fileService")
Call<User> 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<User> call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);

这样就可以将这个文件上传到服务器，但就这样上传操作不够友好，最好加上文件上传进度。而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OkHttp来实现文件上传进度。

我的做法是直接扩展一个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<User> callback = new RetrofitCallback<User>() {
   @Override
    public void onSuccess(Call<User> call, Response<User> response) {

        runOnUIThread(activity, response.body().toString());
        //进度更新结束
    }

    @Override
    public void onFailure(Call<User> 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<User> call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);

回调RetrofitCallback

public abstract class RetrofitCallback<T> implements Callback<T> {

    @Override
    public void onResponse(Call<T> call, Response<T> response) {

        if(response.isSuccessful()) {
            onSuccess(call, response);
        } else {
            onFailure(call, new Throwable(response.message()));
        }
    }

    public abstract void onSuccess(Call<T> call, Response<T> 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 <T>
 */
public final class FileRequestBody<T> extends RequestBody {
  /**
   * 实际请求体
   */
  private RequestBody requestBody;
  /**
   * 上传回调接口
   */
  private RetrofitCallback<T> callback;
  /**
   * 包装完成的BufferedSink
   */
  private BufferedSink bufferedSink;

  public FileRequestBody(RequestBody requestBody, RetrofitCallback<T> 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);
      }
    };
  }
}

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<ResponseBody> downloadFile(@Field("param") String param);

发起请求

RetrofitCallback<ResponseBody> callback = new RetrofitCallback<ResponseBody>() {
    @Override
    public void onSuccess(Call<ResponseBody> call, Response<ResponseBody> 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<ResponseBody> call, Throwable t) {

        runOnUIThread(activity, t.getMessage());
    }
};

Call<ResponseBody> 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（稍后介绍），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。

扩展ResponseBody设置OkHttp拦截器

private <T> RetrofitService getRetrofitService(final RetrofitCallback<T> 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<T>(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 <T>
 */
public final class FileResponseBody<T> extends ResponseBody {
  /**
   * 实际请求体
   */
  private ResponseBody mResponseBody;
  /**
   * 下载回调接口
   */
  private RetrofitCallback<T> mCallback;
  /**
   * BufferedSource
   */
  private BufferedSource mBufferedSource;

  public FileResponseBody(ResponseBody responseBody, RetrofitCallback<T> 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;
      }
    };
  }
}

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<ResponseBody> callback = new RetrofitCallback<ResponseBody>() {
    @Override
    public void onSuccess(Call<ResponseBody> call, Response<ResponseBody> 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<ResponseBody> call, Throwable t) {

        runOnUIThread(activity, t.getMessage());
    }
};

以上就是Retrofit中文件上传下载及其进度更新显示的实现，有疑问的可以加我微信和QQ与我联系，联系方式在这关于