Complete all IoT Monitoring functions

- Add methods for retrieving previous/historical telemetry data
- Use timestamp from Realtime Database to update reload time instead of using timestamp generated on device

lib/data/IoT/models/telemetry_data.dart

@@ -12,4 +12,11 @@ class TelemetryData {
  value: data.value,
  );
  }
+
+ factory TelemetryData.from(String timestamp, String value) {
+ return TelemetryData(
+ timestamp: DateTime.fromMillisecondsSinceEpoch(int.parse(timestamp)),
+ value: value,
+ );
+ }
 }

lib/data/IoT/repositories/telemetry_data_repository.dart

@@ -17,8 +17,43 @@ class TelemetryDataRepository {
  Stream<TelemetryData> readData(String data) {
  return _telemetryDb
  .child(data)
- .orderByValue()
+ .orderByKey()
  .onChildAdded
  .map((event) => TelemetryData.fromRealtimeDatabase(event.snapshot));
  }
+
+ TelemetryData readPreviousReading(String data) {
+ TelemetryData telemetryData;
+ _telemetryDb
+ .child(data)
+ .orderByKey()
+ .limitToLast(1)
+ .onChildAdded
+ .forEach((event) {
+ if (event.snapshot != null) {
+ telemetryData = TelemetryData.fromRealtimeDatabase(event.snapshot);
+ }
+ });
+ return telemetryData;
+ }
+
+ List<TelemetryData> readPreviousReadings(String data, int num) {
+ List<TelemetryData> telemetryDataList = List();
+ _telemetryDb
+ .child(data)
+ .orderByKey()
+ .limitToLast(num)
+ .onValue
+ .forEach((event) {
+ if (event.snapshot != null && event.snapshot.value != null) {
+ Map<dynamic, dynamic> map = event.snapshot.value;
+ map = Map.fromEntries(map.entries.toList()
+ ..sort((e1, e2) => int.parse(e1.key).compareTo(int.parse(e2.key))));
+ map.forEach((key, value) {
+ telemetryDataList.add(TelemetryData.from(key, value));
+ });
+ }
+ });
+ return telemetryDataList;
+ }
 }

lib/ui/IoT/reload_time.dart

@@ -6,8 +6,8 @@ class ReloadTime extends ChangeNotifier {
 
  String get reloadTime => _reloadTime;
 
- void update() {
- _reloadTime = DateFormat('dd-MM-yyyy HH:mm:ss').format(DateTime.now());
+ void update(DateTime timestamp) {
+ _reloadTime = DateFormat('dd-MM-yyyy HH:mm:ss').format(timestamp);
  notifyListeners();
  }
 }

lib/ui/IoT/telemetry_data_card.dart

@@ -98,6 +98,7 @@ class TelemetryDataCard extends StatelessWidget {
  Expanded(
  flex: 2,
  child: TelemetryDataReading(
+ data: cardItem.data,
  reloadTime: reloadTime,
  ),
  ),
@@ -135,6 +136,7 @@ class TelemetryDataCard extends StatelessWidget {
  bottom: 12,
  ),
  child: TelemetryDataChart(
+ data: cardItem.data,
  numData: 6,
  cardItem: cardItem,
  ),

lib/ui/IoT/telemetry_data_chart.dart

@@ -7,12 +7,17 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:intl/intl.dart';
 
 class TelemetryDataChart extends StatelessWidget {
- TelemetryDataChart({Key key, @required this.numData, @required this.cardItem})
- : spots = LineChartSpots(numData),
+ TelemetryDataChart({
+ Key key,
+ @required this.data,
+ @required this.numData,
+ @required this.cardItem,
+ }) : spots = LineChartSpots(numData),
  bottomTitles = FixedSizedQueue(numData),
  xIndexes = Iterable<int>.generate(numData).toList(),
  super(key: key);
 
+ final String data;
  final int numData;
  final LineChartSpots spots;
  final FixedSizedQueue<String> bottomTitles;
@@ -23,9 +28,31 @@ class TelemetryDataChart extends StatelessWidget {
  Widget build(BuildContext context) {
  TelemetryData telemetryData = context.watch<TelemetryData>();
 
+ // If real-time telemetry data is not available,
  if (telemetryData == null) {
- return Container();
- } else {
+ // Tries to read previous telemetry data.
+ // Use Provider.of() method due to stricter restrictions imposed by
+ // context.read() method when it is called inside a build function.
+ List<TelemetryData> telemetryDataList =
+ RepositoryProvider.of<TelemetryDataRepository>(
+ context,
+ listen: false,
+ ).readPreviousReadings(data, numData);
+
+ // Returns an empty container if previous telemetry data is also not available.
+ if (telemetryDataList.length == 0) {
+ return Container();
+ }
+ // Adds previous data into line chart points.
+ else {
+ telemetryDataList.forEach((telemetryData) {
+ spots.add(telemetryData.value);
+ bottomTitles.add(DateFormat.ms().format(telemetryData.timestamp));
+ });
+ }
+ }
+ // If real-time telemetry data is available, add data into line chart points.
+ else {
  spots.add(telemetryData.value);
  bottomTitles.add(DateFormat.ms().format(telemetryData.timestamp));
  }

lib/ui/IoT/telemetry_data_reading.dart

@@ -1,22 +1,40 @@
 import 'package:farmassist/app_theme.dart';
 import 'package:farmassist/data/IoT/models/telemetry_data.dart';
+import 'package:farmassist/data/IoT/repositories/telemetry_data_repository.dart';
 import 'package:farmassist/ui/IoT/reload_time.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:provider/provider.dart';
 
 class TelemetryDataReading extends StatelessWidget {
- const TelemetryDataReading({this.reloadTime});
+ const TelemetryDataReading({@required this.data, this.reloadTime});
 
+ final String data;
  final ReloadTime reloadTime;
 
  @override
  Widget build(BuildContext context) {
  TelemetryData telemetryData = context.watch<TelemetryData>();
 
+ // If real-time telemetry data is not available,
  if (telemetryData == null) {
- return _buildReading('N/A');
+ // Tries to read previous telemetry data.
+ // Use Provider.of() method due to stricter restrictions imposed by
+ // context.read() method when it is called inside a build function.
+ telemetryData = RepositoryProvider.of<TelemetryDataRepository>(
+ context,
+ listen: false,
+ ).readPreviousReading(data);
+ }
+
+ // Returns "N/A" if previous telemetry data is also not available.
+ if (telemetryData == null) {
+ return _buildReading("N/A");
  } else {
- Future.delayed(Duration.zero, () => reloadTime.update());
+ Future.delayed(
+ Duration.zero,
+ () => reloadTime.update(telemetryData.timestamp),
+ );
  return _buildReading(telemetryData.value);
  }
  }