GraphView React-Native CSV reader module

CSVGraph.java

import android.graphics.Color;

import com.facebook.react.bridge.ReadableArray;
import com.facebook.react.bridge.ReadableMap;
import com.facebook.react.modules.core.DeviceEventManagerModule;
import com.facebook.react.uimanager.SimpleViewManager;
import com.facebook.react.uimanager.ThemedReactContext;
import com.facebook.react.uimanager.annotations.ReactProp;
import com.jjoe64.graphview.GraphView;
import com.jjoe64.graphview.GridLabelRenderer;
import com.jjoe64.graphview.helper.DateAsXAxisLabelFormatter;
import com.jjoe64.graphview.series.DataPoint;
import com.jjoe64.graphview.series.LineGraphSeries;
import com.jjoe64.graphview.Viewport;
import com.univocity.parsers.csv.CsvParser;
import com.univocity.parsers.csv.CsvParserSettings;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileFilter;
import java.io.FileReader;
import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.annotation.Nullable;

import org.apache.commons.lang3.time.DurationFormatUtils;
import org.apache.commons.io.comparator.LastModifiedFileComparator;
import org.apache.commons.io.filefilter.WildcardFileFilter;

// Created by Vasyl 25/01/2019
/*
** NOTE: Even though I implemented fastest csv parser on the market, GraphView still struggles to display correctly data greater than 200-300 lines.
** Optimally save to .csv not often than every 3 minutes (assuming really long night sleep: 20 logs per hour x 10 hours of sleep = 200 lines)
*/
// If you want to use it with RN add this file as module.

public class CSVGraph extends SimpleViewManager<GraphView> {
    private final static String REACT_CLASS = "CSV_GRAPH";
    public @Nullable int number;
    ThemedReactContext appContext;

    // Count files in provided directory
    public int getFilesCount(File file) {
      File[] files = file.listFiles();
      int count = 0;
      for (File f : files)
        if (f.isDirectory())
          count += getFilesCount(f);
        else
          count++;

      return count;
    }

    @Override
    public String getName() {
        return REACT_CLASS;
    }

    @Override
    public GraphView createViewInstance(ThemedReactContext reactContext) {
        appContext = reactContext;
        GraphView graphView = new GraphView(reactContext);
        return graphView;
    }

    private void sendData(String eventName, String fileData) {
        appContext
            .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
            .emit(eventName, fileData);
    }

    @ReactProp(name = "graphNumber")
    public void setData(GraphView graphView, @Nullable int number){
        // Get chosen .csv file and if it exists and is not empty, read two first columns: timestamp,value
        // Depending on 'graphNumber' in JS file: the newest file - 0; second - 1; third - 2; ...tenth - 9
        String directoryString = "/storage/emulated/0/SleepTracker/nights/";
        File directory = new File(directoryString);
        graphView.removeAllSeries();
        if (getFilesCount(directory) > 0) {
            FileFilter fileFilter = new WildcardFileFilter("*.csv");
            File[] files = directory.listFiles(fileFilter);
            Arrays.sort(files, LastModifiedFileComparator.LASTMODIFIED_REVERSE);
            String stringFile = directoryString + files[number].getName();
            File file = new File(stringFile);
            if (file.length() > 0) {
                List<String[]> data = new ArrayList<>();
                String[] content = null;
                CsvParserSettings settings = new CsvParserSettings();
                CsvParser parser = new CsvParser(settings);
                String[] rows;
                parser.beginParsing(file);
                String[] firstRow = parser.parseNext();
                while ((rows = parser.parseNext()) != null) {
                    String lastRow = rows[0];
                    content = rows;
                    data.add(content);
                    DataPoint[] points = new DataPoint[data.size()];
                    for (int i = 0; i < data.size(); i++){
                        rows = data.get(i);
                        points[i] = new DataPoint(Long.parseLong(rows[0]), Integer.parseInt(rows[1]));
                    }
                    LineGraphSeries<DataPoint> series = new LineGraphSeries<>(points);
                    graphView.getViewport().setXAxisBoundsManual(true);  
                    graphView.getViewport().setMinX(Long.parseLong(firstRow[0]));
                    graphView.getViewport().setMaxX(Long.parseLong(lastRow));
                    SimpleDateFormat hoursFormat = new SimpleDateFormat("HH':00'");
                    graphView.getGridLabelRenderer().setLabelFormatter(new DateAsXAxisLabelFormatter(appContext, hoursFormat));
                    graphView.getGridLabelRenderer().setNumHorizontalLabels(4);
                    graphView.getGridLabelRenderer().setHorizontalLabelsAngle(135);
                    graphView.getViewport().setScalableY(true);     
                    series.setColor(Color.parseColor("#587F4A"));
                    graphView.addSeries(series);                                              
                    // Change time format depending on scale 
                    graphView.getViewport().setOnXAxisBoundsChangedListener(new Viewport.OnXAxisBoundsChangedListener() {
                        @Override
                        public void onXAxisBoundsChanged(double minX, double maxX, Viewport.OnXAxisBoundsChangedListener.Reason reason) {
                            maxX = graphView.getViewport().getMaxX(false);
                            minX = graphView.getViewport().getMinX(false);
                            Long view = (Double.valueOf(maxX).longValue() / 1000) - (Double.valueOf(minX).longValue() / 1000);
                            SimpleDateFormat hoursFormat;
                            if (view < 100) {
                                hoursFormat = new SimpleDateFormat("HH:mm");
                            } else {
                                hoursFormat = new SimpleDateFormat("HH':00'");
                            }
                            graphView.getGridLabelRenderer().setLabelFormatter(new DateAsXAxisLabelFormatter(appContext, hoursFormat));
                        }
                    });
                    // Send data info
                    String eventName = "INFO_" + String.valueOf(number);
                    String duration = DurationFormatUtils.formatDuration((Long.parseLong(lastRow) - Long.parseLong(firstRow[0])), "HH'h' mm'm'");
                    sendData(eventName, duration);
                }
            } 
        }
    }
}