Some Code

public class SomeCode extends AppCompatActivity {

    private final static long intervalTime = 3000;
    static ArrayList<String> result = new ArrayList<String>();
    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */


    private static String TAG = "FP_" + SomeCode.class.getSimpleName();
    private static String fileCount;
    private static ArrayList<String> imageResult = new ArrayList<>();
    private static ArrayList<SurveyAnsVersionModel> imageResultList = new ArrayList<>();
    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;
    private TabLayout tabLayout;
    private LogisticTaskTabs context;
    private String customFieldData;
    private String userEmail;
    private JSONObject custom_columns;
    private String userID;
    private Handler handler;
    private Runnable updateDataCount;
    private String dirPath;
    private Menu menu;
    private ApiService apiService;
    private CompositeDisposable disposable;

    private static String getFilesCount(String dirPath, int numberOfFiles) {
        File dir = new File(dirPath);
        if (dir.exists()) {
            if (dir.listFiles() == null) {
                numberOfFiles = 0;
                return String.valueOf(numberOfFiles);
            } //it never execute this line even though its null
            else {
                File childfile[] = dir.listFiles();
                Log.i("file no is ", Integer.toString(childfile.length));
                if (childfile.length == 0) {
                    numberOfFiles = 0;
                    return String.valueOf(numberOfFiles);
                } else {
                    numberOfFiles = childfile.length;
                    return String.valueOf(numberOfFiles);
                }
            }
        } else {
            Log.e(TAG, "getFilesCount: Directory doesn't exits", new IOException());
            numberOfFiles = 0;
            return String.valueOf(numberOfFiles);
        }
    }

    private static void getFilesContent(String dirPath) throws FileNotFoundException, JSONException {
        File dir = new File(dirPath);
        result.clear();
        imageResultList.clear();
        if (dir.exists()) {
            if (dir.listFiles() == null) {
                result.clear();
            } //it never execute this line even though its null
            else {
                File childfile[] = dir.listFiles();
                //Log.i("file no is ", Integer.toString(childfile.length));
                if (childfile.length == 0) {
                    result.clear();
                } else {
                    for (File aChildfile : childfile) {

                        String fileOutput = new Scanner(aChildfile).useDelimiter("\\A").next();
                        JSONObject dataObj = new JSONObject(fileOutput);
                        JSONArray dataArr = dataObj.getJSONArray("data");
                        SurveyAnsVersionModel model = new Gson().fromJson(dataObj.toString(), SurveyAnsVersionModel.class);
                        for (int i = 0; i < dataArr.length(); i++) {
                            JSONObject ansObj = dataArr.getJSONObject(i);
                            String type = ansObj.getString("type");
                            String imagePath = ansObj.getString("answer");
                            if (type.equalsIgnoreCase("image") && !TextUtils.isEmpty(imagePath)) {
                                File file = new File(imagePath);
                                if (file.exists()) {
                                    model.setImageFile(file);
                                }
                            }

                        }
                        imageResultList.add(model);
                        result.add(fileOutput);
                    }
                }
            }
        } else {
            Log.e(TAG, "getFilesCount: Directory doesn't exits", new IOException());
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_logistic_task_tabs);

        context = this;
        userEmail = PrefUtils.getUserEmail(context);
        userID = PrefUtils.getUserID(context);
        customFieldData = PrefUtils.getCustomFieldData(context);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        Objects.requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);


        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.viewPager);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        setupViewPager(mViewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);


        tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                //tabLayout.setTitle(tab.getText().toString());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });
        dirPath = context.getExternalFilesDir(null) + "/Answers/u" + userID + "/";
        handler = new Handler();
        updatingFileCountEverySec();

        apiService = ApiClient.getClient(context).create(ApiService.class);
    }

    private void updatingFileCountEverySec() {
        updateDataCount = new Runnable() {
            @Override
            public void run() {

                try {
                    fileCount = getFilesCount(dirPath, 0);
                    MenuItem item = menu.findItem(R.id.action_data_sync);

                    //String dirPath=context.getExternalFilesDir(null) + "/Answers/" + userID +"/";
                    //String count=getFilesCount(dirPath,0);
                    LayerDrawable icon = (LayerDrawable) item.getIcon();
                    setBadgeCount(context, icon, fileCount);
                    invalidateOptionsMenu();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                //Do something after 20 seconds
                handler.postDelayed(updateDataCount, intervalTime);
            }
        };
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_logistic_task_tabs, menu);
        this.menu = menu;
        MenuItem item = menu.findItem(R.id.action_data_sync);
        if (!Data.workOrderType.equalsIgnoreCase(Data.SURVEY))
            item.setVisible(false);
        //String dirPath=context.getExternalFilesDir(null) + "/Answers/" + userID +"/";
        //String count=getFilesCount(dirPath,0);
        LayerDrawable icon = (LayerDrawable) item.getIcon();
        setBadgeCount(this, icon, fileCount);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_data_sync) {
            try {
                getFilesContent(dirPath);
            } catch (FileNotFoundException | JSONException e) {
                e.printStackTrace();
            }
            if (result != null && result.size() > 0) {
                uploadImage();
//                for (int i = 0; i < result.size(); i++) {
//                    String contents = result.get(i);
//
//                }
            }
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        .
        .
        .
        viewPager.setAdapter(adapter);
    }

    @Override
    protected void onResume() {
        super.onResume();
        handler.postDelayed(updateDataCount, intervalTime);
    }

    @Override
    protected void onPause() {
        super.onPause();
        handler.removeCallbacks(updateDataCount);
    }
  

    private JSONObject buildQuestAndAnsJson2(SurveyAnsVersionModel sAVModel) {
        JSONObject object = null;
        try {
            object = new JSONObject();

            int userId = Integer.parseInt(PrefUtils.getUserID(context));
            object.put("company_code", sAVModel.getCompanyCode());
            object.put("type", "submitSurvey");
            object.put("versionid", sAVModel.getVersionid());
            object.put("resubmit", sAVModel.getResubmit());
            JSONArray versionArr = new JSONArray();
            for (SurveyOfflineAnswerModel offlineAnsModel : sAVModel.getAnswers()) {

                JSONObject questObj = new JSONObject();
                questObj.put("slno", offlineAnsModel.getSlno());
                questObj.put("question", offlineAnsModel.getQid());
                questObj.put("type", offlineAnsModel.getType());
                questObj.put("qid", offlineAnsModel.getQid());
                questObj.put("optionId", offlineAnsModel.getOptionId());
                questObj.put("answer", offlineAnsModel.getAnswer());
                questObj.put("skipped", offlineAnsModel.getSkipped());
                versionArr.put(questObj);
            }
            //Log.d(TAG, "onBtnNextClicked: FinalFrom -> \n" + versionArr);
            object.put("data", versionArr);


        } catch (JSONException e) {
            e.printStackTrace();
        }
        return object;
    }

    private ObservableSource<ResponseBody> getSubmitResponse(JSONObject datajson) {

        RequestBody body = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), (datajson.toString()));
        return apiService.submitSurvey2(body);

    }

    void resetData(String imageURL, SurveyAnsVersionModel ansVersionModel) {
        int quesOrderNo = -1;
        Pattern pattern = Pattern.compile("_Q(.*?)_");
        Matcher matcher = pattern.matcher(imageURL);
        if (matcher.find()) {
            quesOrderNo = Integer.parseInt(matcher.group(1));
        }

        if (quesOrderNo != -1) {
            File file = ansVersionModel.getImageFile();
            if (file.exists()) {
                boolean isFileDeleted = file.delete();
                Log.d(TAG, "resetData() isFileDeleted: " + isFileDeleted);
            }
            for (SurveyOfflineAnswerModel offlineAnswerModel :
                    ansVersionModel.getAnswers()) {
                if (offlineAnswerModel.getQid().equals(quesOrderNo)) {
                    offlineAnswerModel.setAnswer(imageURL);
                }
            }
        }

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    void uploadImage() {
        for (int i = 0; i < imageResultList.size(); i++) {
            SurveyAnsVersionModel ansVersionModel = imageResultList.get(i);
            Observable<ResponseBody> getuploadMultiFile2 = apiService.uploadMultiFile2(buildImageReqJSon(ansVersionModel));
            getuploadMultiFile2
                    .concatMap(new Function<ResponseBody, ObservableSource<ResponseBody>>() {
                        @Override
                        public ObservableSource<ResponseBody> apply(ResponseBody responseBody) throws Exception {
                            String res1 = responseBody.string();
                            JSONObject resObj = new JSONObject(res1);
                            if (resObj.optBoolean("success")) {
                                resetData(resObj.getString("imageURL"), ansVersionModel);
                            } else {
                                throw new RuntimeException("Unable to upload image"); // this will be thorwn to onError
                            }
                            JSONObject obj = buildQuestAndAnsJson2(ansVersionModel);
                            return getSubmitResponse(obj);
                        }
                    }).map(new Function<ResponseBody, String>() {
                @Override
                public String apply(ResponseBody responseBody) throws Exception {
                    String res = responseBody.string();
                    Log.d(TAG, "apply() returned: " + res);
                    return res;
                }
            })
                    .subscribeOn(Schedulers.newThread())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new Observer<String>() {
                        @Override
                        public void onSubscribe(Disposable d) {
                            Log.d(TAG, " onSubscribe : " + d.isDisposed());
                        }

                        @Override
                        public void onNext(String s) {
                            Log.d(TAG, "onNext() returned: " + s);
                            try {
                                JSONObject sObj = new JSONObject(s);
                                boolean isSuccess = sObj.getBoolean("success");

                                if (isSuccess) {
                                    int uid = sObj.getInt("uid");
                                    int versionid = sObj.getInt("versionid");
                                    int woid = sObj.getInt("woid");
                                    int cid = sObj.getInt("cid");
                                    deletefile(uid, versionid, woid, cid);
                                }

                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }

                        @Override
                        public void onError(Throwable e) {
                            e.printStackTrace();
                        }

                        @Override
                        public void onComplete() {
                            Log.d(TAG, " onComplete");
                        }
                    });
        }

    }

    private MultipartBody buildImageReqJSon2(ArrayList<SurveyAnsVersionModel> versionModels) {
        MultipartBody requestBody = null;
        for (int i = 0; i < versionModels.size(); i++) {
            SurveyAnsVersionModel ansVersionModel = versionModels.get(i);

            try {
                MultipartBody.Builder builder = new MultipartBody.Builder();
                builder.setType(MultipartBody.FORM);


                JSONObject formObj = new JSONObject();


                File file = ansVersionModel.getImageFile();
                builder.addFormDataPart("filename[]", file.getName(), RequestBody.create(MediaType.parse("multipart/form-data"), file));
                formObj.put("description", ansVersionModel.getdesc());
                builder.addFormDataPart("data", formObj.toString());

                requestBody = builder.build();

            } catch (JSONException e) {
                e.printStackTrace();
            }
        }

        return requestBody;

    }

    private MultipartBody buildImageReqJSon(SurveyAnsVersionModel ansVersionModel) {
        MultipartBody requestBody = null;
        try {
            MultipartBody.Builder builder = new MultipartBody.Builder();
            builder.setType(MultipartBody.FORM);


            JSONObject formObj = new JSONObject();


            File file = ansVersionModel.getImageFile();
            builder.addFormDataPart("filename[]", file.getName(), RequestBody.create(MediaType.parse("multipart/form-data"), file));
            //formObj.put("qid", questionModel.getId());

            //            builder.addFormDataPart("qid", String.valueOf(questionModel.getId()));
            //            builder.addFormDataPart("slno", String.valueOf(questionModel.getQuesOrderNo()));

            formObj.put("versionid", ansVersionModel.getVersionid());
            formObj.put("company_code", ansVersionModel.getCompanyCode());
            formObj.put("woid", ansVersionModel.getWoid());
            builder.addFormDataPart("data", formObj.toString());

            requestBody = builder.build();

        } catch (JSONException e) {
            e.printStackTrace();
        }
        return requestBody;
    }

    void deletefile(int uid, int vid, int woid, int cid) {
        String dirPath = context.getExternalFilesDir(null) + "/Answers/u" + uid + "/";
        final File folder = new File(dirPath);
        String filename = "survey_v" + vid + "_c" + cid + "_w" + woid + ".json";
        final File[] files = folder.listFiles(new FilenameFilter() {
            @Override
            public boolean accept(final File dir,
                                  final String name) {
                return name.matches(filename);
            }
        });
        for (final File file : files) {
            if (!file.delete()) {
                Log.d(TAG, "deletefile() returned: Can't remove" + file.getAbsolutePath());
            }
        }
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}