Retrofit+RxJava实现带进度下载文件

compile 'io.reactivex:rxjava:1.1.0'
compile 'io.reactivex:rxandroid:1.1.0'
compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'
compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'
compile 'com.squareup.retrofit2:adapter-rxjava:2.0.0-beta4'

/**
 * Description: 下载进度回调
 * Created by jia on 2017/11/30.
 * 人之所以能，是相信能
 */
public interface JsDownloadListener {

 void onStartDownload();

 void onProgress(int progress);

 void onFinishDownload();

 void onFail(String errorInfo);

}

/**
 * Description: 带进度 下载请求体
 * Created by jia on 2017/11/30.
 * 人之所以能，是相信能
 */
public class JsResponseBody extends ResponseBody {

 private ResponseBody responseBody;

 private JsDownloadListener downloadListener;

 // BufferedSource 是okio库中的输入流，这里就当作inputStream来使用。
 private BufferedSource bufferedSource;

 public JsResponseBody(ResponseBody responseBody, JsDownloadListener downloadListener) {
 this.responseBody = responseBody;
 this.downloadListener = downloadListener;
 }

 @Override
 public MediaType contentType() {
 return responseBody.contentType();
 }

 @Override
 public long contentLength() {
 return responseBody.contentLength();
 }

 @Override
 public BufferedSource source() {
 if (bufferedSource == null) {
 bufferedSource = Okio.buffer(source(responseBody.source()));
 }
 return bufferedSource;
 }

 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);
 // read() returns the number of bytes read, or -1 if this source is exhausted.
 totalBytesRead += bytesRead != -1 ? bytesRead : 0;
 Log.e("download", "read: "+ (int) (totalBytesRead * 100 / responseBody.contentLength()));
 if (null != downloadListener) {
  if (bytesRead != -1) {
  downloadListener.onProgress((int) (totalBytesRead * 100 / responseBody.contentLength()));
  }

 }
 return bytesRead;
 }
 };

 }
}

/**
 * Description: 带进度 下载 拦截器
 * Created by jia on 2017/11/30.
 * 人之所以能，是相信能
 */
public class JsDownloadInterceptor implements Interceptor {

 private JsDownloadListener downloadListener;

 public JsDownloadInterceptor(JsDownloadListener downloadListener) {
 this.downloadListener = downloadListener;
 }

 @Override
 public Response intercept(Chain chain) throws IOException {
 Response response = chain.proceed(chain.request());
 return response.newBuilder().body(
 new JsResponseBody(response.body(), downloadListener)).build();
 }
}

/**
 * Description:
 * Created by jia on 2017/11/30.
 * 人之所以能，是相信能
 */
public interface DownloadService {

 @Streaming
 @GET
 Observable<ResponseBody> download(@Url String url);

}

/**
 1. Description: 下载工具类
 2. Created by jia on 2017/11/30.
 3. 人之所以能，是相信能
 */
public class DownloadUtils {

 private static final String TAG = "DownloadUtils";

 private static final int DEFAULT_TIMEOUT = 15;

 private Retrofit retrofit;

 private JsDownloadListener listener;

 private String baseUrl;

 private String downloadUrl;

 public DownloadUtils(String baseUrl, JsDownloadListener listener) {

 this.baseUrl = baseUrl;
 this.listener = listener;

 JsDownloadInterceptor mInterceptor = new JsDownloadInterceptor(listener);

 OkHttpClient httpClient = new OkHttpClient.Builder()
 .addInterceptor(mInterceptor)
 .retryOnConnectionFailure(true)
 .connectTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
 .build();

 retrofit = new Retrofit.Builder()
 .baseUrl(baseUrl)
 .client(httpClient)
 .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
 .build();
 }

 /**
 * 开始下载
 *
 * @param url
 * @param filePath
 * @param subscriber
 */
 public void download(@NonNull String url, final String filePath, Subscriber subscriber) {

 listener.onStartDownload();

 // subscribeOn()改变调用它之前代码的线程
 // observeOn()改变调用它之后代码的线程
 retrofit.create(DownloadService.class)
 .download(url)
 .subscribeOn(Schedulers.io())
 .unsubscribeOn(Schedulers.io())
 .map(new Func1<ResponseBody, InputStream>() {

  @Override
  public InputStream call(ResponseBody responseBody) {
  return responseBody.byteStream();
  }
 })
 .observeOn(Schedulers.computation()) // 用于计算任务
 .doOnNext(new Action1<InputStream>() {
  @Override
  public void call(InputStream inputStream) {

  writeFile(inputStream, filePath);

  }
 })
 .observeOn(AndroidSchedulers.mainThread())
 .subscribe(subscriber);

 }

 /**
 * 将输入流写入文件
 *
 * @param inputString
 * @param filePath
 */
 private void writeFile(InputStream inputString, String filePath) {

 File file = new File(filePath);
 if (file.exists()) {
 file.delete();
 }

 FileOutputStream fos = null;
 try {
 fos = new FileOutputStream(file);

 byte[] b = new byte[1024];

 int len;
 while ((len = inputString.read(b)) != -1) {
 fos.write(b,0,len);
 }
 inputString.close();
 fos.close();

 } catch (FileNotFoundException e) {
 listener.onFail("FileNotFoundException");
 } catch (IOException e) {
 listener.onFail("IOException");
 }

 }
}