Make it possible to save/load fitness measurements

This required me wrapping the new Activity APIs
as well as adding the missing pubspec.yaml

@abarth

examples/fitness/lib/fitness_item.dart

@@ -9,11 +9,15 @@ typedef void FitnessItemHandler(FitnessItem item);
 const double kFitnessItemHeight = 79.0;
 
 abstract class FitnessItem {
+  FitnessItem.fromJson(Map json) : when = DateTime.parse(json['when']);
+
   FitnessItem({ this.when }) {
     assert(when != null);
   }
   final DateTime when;
 
+  Map toJson() => { 'when' : when.toIso8601String() };
+
   // TODO(jackson): Internationalize
   String get displayDate => "${when.year.toString()}-${when.month.toString().padLeft(2,'0')}-${when.day.toString().padLeft(2,'0')}";
 

examples/fitness/lib/main.dart

@@ -8,6 +8,7 @@ import 'package:sky/editing/input.dart';
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/theme/colors.dart' as colors;
 import 'package:sky/widgets.dart';
+import 'user_data.dart';
 
 part 'feed.dart';
 part 'fitness_item.dart';
@@ -19,10 +20,21 @@ part 'settings.dart';
 class FitnessApp extends App {
 
   NavigationState _navigationState;
-  final List<FitnessItem> _userData = [
-    new Measurement(weight: 180.0, when: new DateTime.now().add(const Duration(days: -1))),
-    new Measurement(weight: 160.0, when: new DateTime.now()),
-  ];
+  final List<FitnessItem> _userData = [];
+
+  void didMount() {
+    super.didMount();
+    loadFitnessData().then((List<Measurement> list) {
+      setState(() {
+        _userData.addAll(list);
+      });
+    }).catchError((e) => print("Failed to load data: $e"));
+  }
+
+  void save() {
+    saveFitnessData(_userData)
+      .catchError((e) => print("Failed to load data: $e"));
+  }
 
   void initState() {
     _navigationState = new NavigationState([
@@ -71,12 +83,14 @@ class FitnessApp extends App {
     setState(() {
       _userData.add(item);
       _userData.sort((a, b) => a.when.compareTo(b.when));
+      save();
     });
   }
 
   void _handleItemDeleted(FitnessItem item) {
     setState(() {
       _userData.remove(item);
+      saveFitnessData(_userData);
     });
   }
 

examples/fitness/lib/measurement.dart

@@ -6,12 +6,20 @@ part of fitness;
 
 class Measurement extends FitnessItem {
   Measurement({ DateTime when, this.weight }) : super(when: when);
+  Measurement.fromJson(Map json) : super.fromJson(json), weight = json['weight'];
 
   final double weight;
 
   // TODO(jackson): Internationalize
   String get displayWeight => "${weight.toStringAsFixed(2)} lbs";
 
+  @override
+  Map toJson() {
+    Map json = super.toJson();
+    json['weight'] = weight;
+    return json;
+  }
+
   FitnessItemRow toRow({ FitnessItemHandler onDismissed }) {
     return new MeasurementRow(measurement: this, onDismissed: onDismissed);
   }

examples/fitness/lib/user_data.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io';
+import 'dart:async';
+
+import 'package:path/path.dart' as path;
+
+import 'main.dart';
+import 'package:sky/mojo/activity.dart';
+
+String cachedDataFilePath = null;
+
+Future<String> dataFilePath() async {
+  if (cachedDataFilePath == null) {
+    String dataDir = await getFilesDir();
+    cachedDataFilePath = path.join(dataDir, 'data.json');
+  }
+  return cachedDataFilePath;
+}
+
+Future<List<Measurement>> loadFitnessData() async {
+  List<Measurement> items = [];
+  String dataPath = await dataFilePath();
+  print("Loading from $dataPath");
+  JsonDecoder decoder = new JsonDecoder();
+  var data = await decoder.convert(await new File(dataPath).readAsString());
+  data.forEach((item) {
+    items.add(new Measurement.fromJson(item));
+  });
+  return items;
+}
+
+// Intentionally synchronous for execution just before shutdown.
+Future saveFitnessData(List<Measurement> data) async {
+  String dataPath = await dataFilePath();
+  print("Saving to $dataPath");
+  JsonEncoder encoder = new JsonEncoder();
+  String contents = await encoder.convert(data);
+  File dataFile = await new File(dataPath).writeAsString(contents);
+  print("Success! $dataFile");
+}

examples/fitness/pubspec.yaml

+name: fitness
+dependencies:
+  sky: any
+  sky_tools: any
+dependency_overrides:
+  path: "^1.3.6"
+  material_design_icons:
+    path: ../../sky/packages/material_design_icons
+  sky:
+    path: ../../sky/packages/sky

packages/flutter/lib/mojo/activity.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:sky';
+import 'dart:async';
 
 import 'package:sky/mojo/shell.dart' as shell;
 import 'package:sky_services/activity/activity.mojom.dart';
@@ -53,3 +54,7 @@ void updateTaskDescription(String label, Color color) {
 
   _activity.ptr.setTaskDescription(description);
 }
+
+Future<String> getFilesDir() async => (await _activity.ptr.getFilesDir()).path;
+
+Future<String> getCacheDir() async => (await _activity.ptr.getCacheDir()).path;