private <T> T getRetrofit(Class<T> T) {
    retrofit = new Retrofit.Builder()
            .client(getOkHttpClient())
            .baseUrl(url)
            .addConverterFactory(GsonConverterFactory.create())
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build();
    return retrofit.create(T);
}

private OkHttpClient getOkHttpClient(){
    OkHttpClient okHttpClient = new OkHttpClient.Builder()
            .connectTimeout(20 * 1000, TimeUnit.MILLISECONDS)
            .addNetworkInterceptor(new Interceptor() {
                @Override
                public okhttp3.Response intercept(Chain chain) throws IOException {
                    okhttp3.Response orginalResponse = chain.proceed(chain.request());
                    return orginalResponse.newBuilder()
                            .body(new ProgressResponseBody(orginalResponse.body(), new ProgressListener() {
                                @Override
                                public void onProgress(long progress, long total, boolean done) {
                                    Logger.i(TAG + " %s"+" %s", "onProgress: " + "total ----> " + total
                                            + " done ---->" + progress,progress * 100 / total, Looper.myLooper());
                                    updateNotification(progress * 100 / total);
                                }
                            }))
                            .build();
                }
            })
            .build();
    return okHttpClient;
}

    /**
     * 初始化Notification通知
     */
    public void initNotification() {
        builder = new NotificationCompat.Builder(mContext)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentText("0%")
                .setContentTitle("App更新")
                .setProgress(100, 0, false);
        notificationManager = (NotificationManager) mContext
                .getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(NOTIFY_ID, builder.build());
    }

    /**
     * 更新通知
     */
    public void updateNotification(long progress) {
        int currProgress = (int) progress;
        if (preProgress < currProgress) {
            builder.setContentText(progress + "%");
            builder.setProgress(100, currProgress, false);
            notificationManager.notify(NOTIFY_ID, builder.build());
        }
        preProgress =  currProgress;
    }

    /**
     * 取消通知
     */
    public void cancelNotification() {
        notificationManager.cancel(NOTIFY_ID);
    }

    IDownloadApi iDownloadApi = getRetrofit(IDownloadApi.class);
    iDownloadApi.loadFile()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Observer<ResponseBody>() {
                @Override
                public void onSubscribe(@NonNull Disposable d) {
                    Logger.i(TAG,"onSubscribe");
                    mCompositeDisposable.add(d);
                }

                @Override
                public void onNext(@NonNull ResponseBody responseBody) {
                    Logger.i(TAG,"onNext");
                    File file = null;
                    try {
                        file = DownloadUtils.getInstance(fileDir,fileName).saveFile(responseBody);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    installApk(file);
                    cancelNotification();
                }

                @Override
                public void onError(@NonNull Throwable e) {
                    Logger.e(TAG +" %s","onError "+e.getMessage(),e);
                    cancelNotification();
                }

                @Override
                public void onComplete() {
                    Logger.i(TAG,"onComplete");
                }
            });

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org>