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

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@Multipart @POST("fileService") Call<User> uploadFile(@Part MultipartBody.Part file);

构造请求体上传

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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

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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

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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

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/** * 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

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//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

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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

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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

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/** * 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

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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