基于Ok+Rxjava实现断点续传下载

/**
 * 开始下载
 * @param url 下载请求的网址
 * @param downFileCallback 用来回调的接口
 */
 public void download(final String url, final DownFileCallback downFileCallback) {
 if (url == null || downCalls.get(url) != null) {
 return;
 }
 Observable.just(url)
 .filter(new Predicate<String>() {
  @Override
  public boolean test(String s) throws Exception {
  //过滤条件 若map中存在，则这次不下载
  return !downCalls.containsKey(s);
  }
 })
 .flatMap(new Function<String, ObservableSource<DownloadInfo>>() {
  @Override
  public ObservableSource<DownloadInfo> apply(String s) throws Exception {
  //创建下载实体类
  return Observable.just(createDownInfo(s));
  }
 })
 .map(new Function<DownloadInfo, DownloadInfo>() {
  @Override
  public DownloadInfo apply(DownloadInfo s) throws Exception {
  //根据本地是否存在此文件，来设置文件名及文件初始下载大小
  return getRealFileName(s);
  }
 })
 .flatMap(new Function<DownloadInfo, ObservableSource<DownloadInfo>>() {
  @Override
  public ObservableSource<DownloadInfo> apply(DownloadInfo downloadInfo) throws Exception {
  //创建被观察者
  return Observable.create(new DownloadSubscribe(downloadInfo));
  }
 })//下载
 .observeOn(AndroidSchedulers.mainThread())//在主线程回调
 .subscribeOn(Schedulers.io())//在子线程执行
 .subscribe(new DownLoadObserver() {//添加观察者
  @Override
  public void onNext(DownloadInfo downloadInfo) {
  super.onNext(downloadInfo);
  downFileCallback.onProgress(downloadInfo.getTotal(), downloadInfo.getProgress());
  }
 
  @Override
  public void onError(Throwable e) {
  super.onError(e);
  if (!(e instanceof SocketException)) {
  downFileCallback.onFail(e.getMessage());
  }
 
  }
 
  @Override
  public void onComplete() {
  downFileCallback.onSuccess(url);
  }
 
 });
 }

/**
 * 根据url暂停下载操作
 * @param url
 */
 public void cancel(String url) {
 Call call = downCalls.get(url);
 if (call != null) {
 call.cancel();//取消
 }
 downCalls.remove(url);
 }

 /**
 * 创建被观察者DownloadSubscribe
 */
 private class DownloadSubscribe implements ObservableOnSubscribe<DownloadInfo> {
 private DownloadInfo downloadInfo;
 
 public DownloadSubscribe(DownloadInfo downloadInfo) {
 this.downloadInfo = downloadInfo;
 }
 
 @Override
 public void subscribe(ObservableEmitter<DownloadInfo> e) throws Exception {
 String url = downloadInfo.getUrl();
 long downloadLength = downloadInfo.getProgress();//已经下载好的长度
 long contentLength = downloadInfo.getTotal();//文件的总长度
 //初始进度信息
 e.onNext(downloadInfo);
 
 Request request = new Request.Builder()
  //断点续传的核心
  .addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
  .url(url)
  .build();
 Call call = mClient.newCall(request);
 //根据下载url，把call存放在map中，取消的时候就可以通过call.cancle()来实现
 downCalls.put(url, call);
 Response response = call.execute();
 
 File file = new File(getTemporaryPath(), downloadInfo.getFileName());
 InputStream is = null;
 FileOutputStream fileOutputStream = null;
 try {
 is = response.body().byteStream();
 fileOutputStream = new FileOutputStream(file, true);
 byte[] buffer = new byte[2048];//缓冲数组2kB
 int len;
 while ((len = is.read(buffer)) != -1) {
  fileOutputStream.write(buffer, 0, len);
  downloadLength += len;
  downloadInfo.setProgress(downloadLength);
  e.onNext(downloadInfo);
 }
 fileOutputStream.flush();
 downCalls.remove(url);
 } finally {
 //关闭IO流
 IOUtil.closeAll(is, fileOutputStream);
 
 }
 e.onComplete();//完成
 }
 }

/**
 * 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(本地存在地址).download(url1, new DownFileCallback() {
  @Override
  public void onProgress(long totalSize, long downSize) {
  progress1.setMax((int) totalSize);
  progress1.setProgress((int) downSize);
  }
 
  @Override
  public void onSuccess(String url) {
  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();
  }
 });