Retrofit文件下载

 String baseUrl="http://cdn.banmi.com/";
    @GET("banmiapp/apk/banmi_330.apk")
    @Streaming
    Observable<ResponseBody> down();

添加权限

  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.INTERNET" />

代码

private void retrofit() {
        Retrofit retrofit = new Retrofit.Builder().addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .baseUrl(ApiServicer.baseUrl)
                .build();

        Observable<ResponseBody> down = retrofit.create(ApiServicer.class).down();

        down.subscribeOn(Schedulers.io())
                //因为要写文件,所以Observer不切换到主线程
                .subscribe(new Observer<ResponseBody>() {

                    private int progrss;

                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(ResponseBody responseBody) {
                        InputStream inputStream = responseBody.byteStream();
                        long maxx = responseBody.contentLength();
                        String path = Environment.getExternalStorageDirectory() + File.separator + "banmi_330.apk";

                        File file = new File(path);

                        if (!file.exists()) {
                            try {
                                file.createNewFile();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }

                        try {
                            FileOutputStream fileOutputStream = new FileOutputStream(file);

                            byte[] bytes = new byte[1024];

                            int rendLength = 0;
                            long currLength = 0;

                            while ((rendLength = inputStream.read(bytes)) != -1) {
                                fileOutputStream.write(bytes, 0, rendLength);
                                currLength += rendLength;

                                progrss = (int) (currLength * 100 / maxx);
                                progressBar.setProgress(progrss);

                                runOnUiThread(new Runnable() {
                                    @Override
                                    public void run() {
                                        Result.setText(progrss+"%");
                                    }
                                });


//                                Message message = new Message();
//                                message.what=0;
//                                message.obj=progrss;
//                                handler.sendMessage(message);

                            }

                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    if (progrss == 100) {
                                        Toast.makeText(MainActivity.this, "下载成功", Toast.LENGTH_SHORT).show();

                                    }
                                }
                            });
                            inputStream.close();
                            fileOutputStream.close();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                });
    }