基于Ok+Rxjava+retrofit实现断点续传下载

public class DownloadResponseBody extends ResponseBody {
 private ResponseBody responseBody;
 
 //进度回调接口
 private DownFileCallback downFileCallback;
 
 private BufferedSource bufferedSource;
 private String downUrl;
 
 
 public DownloadResponseBody(ResponseBody responseBody, DownFileCallback downFileCallback, String downUrl) {
 this.responseBody = responseBody;
 this.downFileCallback = downFileCallback;
 this.downUrl = downUrl;
 }
 
 @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;
 File file = new File(DownloadManager.getInstance().getTemporaryName(downUrl));
 
 @Override
 public long read(Buffer sink, long byteCount) throws IOException {
 long bytesRead = super.read(sink, byteCount);
 totalBytesRead += bytesRead != -1 ? bytesRead : 0;
 if (null != downFileCallback) {
 if (bytesRead != -1) {
 long loacalSize = file.length();//本地已下载的长度
 long trueTotal = loacalSize + responseBody.contentLength() - totalBytesRead;//文件真实长度
 downFileCallback.onProgress(trueTotal,loacalSize);
 } else {
 
 }
 
 }
 return bytesRead;
 }
 };
 
 }
}

public class Downloadinterceptor implements Interceptor {
 
 private DownFileCallback downFileCallback;
 
 private String downUrl;
 
 public Downloadinterceptor(DownFileCallback listener,String downUrl) {
 this.downFileCallback = listener;
 this.downUrl = downUrl;
 }
 
 @Override
 public Response intercept(Chain chain) throws IOException {
 Response response = chain.proceed(chain.request());
 
 return response.newBuilder()
 .body(new DownloadResponseBody(response.body(), downFileCallback,downUrl))
 .build();
 }
}

public interface HttpService {
 
 /*大文件需要加入Streaming这个判断，防止下载过程中写入到内存中,造成oom*/
 @Streaming
 @GET
 Observable<ResponseBody> download(@Header("range") String start, @Url String url);
}

 /**
 * 开始下载
 * @param url 下载地址
 * @param downFileCallback 进度回调接口
 */
 public void download(final String url, final DownFileCallback downFileCallback) {
 /*正在下载不处理*/
 if (url == null || submap.get(url) != null) {
 return;
 }
 
 Downloadinterceptor interceptor = new Downloadinterceptor(downFileCallback, url);
 okHttpClient = new OkHttpClient.Builder()
 .addInterceptor(interceptor)
 .build();
 Retrofit retrofit = new Retrofit.Builder()
 .client(okHttpClient)
 .baseUrl("http://imtt.dd.qq.com")
 .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
 .build();
 final HttpService httpservice = retrofit.create(HttpService.class);
 
 ProgressDownSubscriber subscriber =
 Observable.just(url)
 .flatMap(new Function<String, ObservableSource<DownloadInfo>>() {
 @Override
 public ObservableSource<DownloadInfo> apply(String s) throws Exception {
 return Observable.just(createDownInfo(s));
 }
 })
 .map(new Function<DownloadInfo, DownloadInfo>() {
 @Override
 public DownloadInfo apply(DownloadInfo s) throws Exception {
 return getRealFileName(s);
 }
 })
 .flatMap(new Function<DownloadInfo, Observable<ResponseBody>>() {
 @Override
 public Observable<ResponseBody> apply(DownloadInfo downInfo) throws Exception {
 return httpservice.download("bytes=" + downInfo.getProgress() + "-", downInfo.getUrl());
 }
 })//下载
 .map(new Function<ResponseBody, DownloadInfo>() {
 @Override
 public DownloadInfo apply(ResponseBody responsebody) {
 try {
 return writecache(responsebody, url);
 } catch (IOException e) {
 //*失败抛出异常*//
 e.printStackTrace();
 }
 return null;
 }
 })
 .observeOn(AndroidSchedulers.mainThread())//在主线程回调
 .subscribeOn(Schedulers.io())//在子线程执行
 .subscribeWith(new ProgressDownSubscriber<DownloadInfo>() {
 @Override
 public void onNext(DownloadInfo downInfo) {
 downFileCallback.onSuccess(downInfo);
 submap.remove(downInfo.getUrl());
 }
 
 @Override
 public void onError(Throwable t) {
 downFileCallback.onFail(t.getMessage());
 submap.remove(url);
 }
 });
 
 
 submap.put(url, subscriber);
 }

 /**
 * 暂停下载
 */
 public void stop(String url) {
 if (url == null) return;
 if (submap.containsKey(url)) {
 ProgressDownSubscriber subscriber = submap.get(url);
 subscriber.dispose();
 submap.remove(url);
 }
 }

/**
 * 从服务器获取文件长度
 *
 * @param downloadUrl
 * @return
 */
 private long getContentLength(String downloadUrl) {
 Request request = new Request.Builder()
 .url(downloadUrl)
 .build();
 try {
 Response response = mClient.newCall(request).execute();
 if (response != null && response.isSuccessful()) {
 long contentLength = response.body().contentLength();
 response.close();
 return contentLength == 0 ? DownloadInfo.TOTAL_ERROR : contentLength;
 }
 } catch (IOException e) {
 e.printStackTrace();
 }
 return DownloadInfo.TOTAL_ERROR;
 }

DownloadManager.getInstance().downloadPath(本地存放地址).download(url1, new DownFileCallback() {
 @Override
 public void onSuccess(DownloadInfo info) {
 
 Toast.makeText(MainActivity.this, url1 + "下载完成", Toast.LENGTH_SHORT).show();
 }
 
 @Override
 public void onFail(String msg) {
 Toast.makeText(MainActivity.this, url1 + "下载失败", Toast.LENGTH_SHORT).show();
 }
 
 @Override
 public void onProgress(final long totalSize, final long downSize) {
 // 需要注意的是，如果文件总大小为50M，已下载的大小为10M，
 // 再次下载时onProgress返回的totalSize是文件总长度
 // 减去 已下载大小 10M， 即40M，downSize为本次下载的已下载量
 // 好消息是，我已经在内部做过处理，放心使用吧，但是这个问题大家还是要知道的
 
 runOnUiThread(new Runnable() {
 @Override
 public void run() {
 int progress = (int) (downSize * 100 / totalSize);
 progress1.setProgress(progress);
 }
 });
 }
 });