Nullsafety (#586)

* Work in progress

* lib/** nullability compliant;
added linter exceptions for string single quotes and pedantic local variable type rule

* Example:: updated to nullsafe-ready dependencies

* Example:: nullsafety + refactor WIP

* Example:: nullsafe ready

* Example/test:: nullsafe ready

* test:: using new mocking mechanism
additional fixes

* Java: added some null checks to make the calls to stop and destroy reentrant

* Example:: additional cleanup and refactor
Lib:: enchanced error handling, refined nullability on certain types

* TestFix:: the injected manager instance is not part of the Characteristic POD so should be ignored when checking for equallity

* ble_error seem to have rather nullable fields

* TestFix: little refactor on characteristic_mixin regarding clearity and type annotations

* TestFix:: lib_core_test::  tests now passing

* Example:: removed comment-disabled code

* Test:: all tests Passing now! 🎉

* Enhanced BleError nullability, so that reason always has a default value;
made fields final

* Travis fix

* disabled analysis for tests

* Travis:: still fixing ios build

* vscode:: stopped tracking settings file

* travis:: removed my additions to ios example script

* Characteristic:: Service field is now final

* gitignored andoid related staff
xcode noise

* Add bluetooth-central key to README.md (#562)

* Add bluetooth-central key to README.md

Based on #530

* Update README.md

* Travis: updated xcode version to 12.2

* BleError:: default reason text added

* ScanResult::
added final qualifiers
isConnectable is back to nullable since it's only available on iOS on android it will be null which does not mean false!!

* CharacteristicsMixin::
_parseCharacteristicWithValueWithTransactionIdResponse()::
signature is now type safe
moved the rawJsonValue String checking to the caller side

* Test:: removed dummy print

* ScanningMixin:: _prepareScanEventsStream() renamed to just _scanEvents
also _resetScanEvents introduced to null the underlying scream out

* ScanningMixin:: small refinement on naming stuff

* Characteristic:: refactor on Futures to always complete with something even if withResponse is false
additional type safety on invokeMethod calls

* Revert "Characteristic:: refactor on Futures to always complete with something even if withResponse is false"

This reverts commit 86dafd6.

Co-authored-by: Yauheni Pakala <[email protected]>

.gitignore

@@ -14,4 +14,8 @@ lib/generated/
 example/lib/generated/
 example/.flutter-plugins-dependencies
 .dart_tool/
-example/ios/Podfile.lock
+example/ios/Podfile.lock
+.vscode/settings.json
+org.eclipse.buildship.core.prefs
+.project
+.classpath

.travis.yml

@@ -47,7 +47,7 @@ _android_job_template: &android_job_template
 _ios_job_template: &ios_job_template
   language: objective-c
   os: osx
-  osx_image: xcode11.6
+  osx_image: xcode12.2
   xcode_workspave: example/ios/Runner.xcworkspace
   xcode_scheme: Runner
   before_script:

README.md

@@ -49,6 +49,19 @@ Add [Privacy - Bluetooth Always Usage Description](https://developer.apple.com/d
 ...
 ```
 
+#### Background mode
+
+To support background capabilities add [The `bluetooth-central` Background Execution Mode](https://developer.apple.com/library/archive/documentation/NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/CoreBluetoothBackgroundProcessingForIOSApps/PerformingTasksWhileYourAppIsInTheBackground.html#//apple_ref/doc/uid/TP40013257-CH7-SW6) key to `[project]/ios/Runner/Info.plist` file.
+
+```xml
+...
+<key>UIBackgroundModes</key>
+<array>
+  <string>bluetooth-central</string>
+</array>
+...
+```
+
 ## Usage
 
 The library is organised around a few base entities, which are:

analysis_options.yaml

@@ -1 +1,10 @@
-include: package:pedantic/analysis_options.yaml
+include: package:pedantic/analysis_options.yaml
+
+analyzer:
+  exclude: [test/**]
+
+linter:
+  rules:
+    prefer_single_quotes: false
+    omit_local_variable_types: false
+    unawaited_futures: false

android/src/main/java/com/polidea/flutter_ble_lib/FlutterBleLibPlugin.java

@@ -149,7 +149,9 @@ public void onEvent(Integer restoreStateIdentifier) {
     }
 
     private void destroyClient(Result result) {
-        bleAdapter.destroyClient();
+        if (bleAdapter != null) {
+            bleAdapter.destroyClient();
+        }
         scanningStreamHandler.onComplete();
         connectionStateStreamHandler.onComplete();
         bleAdapter = null;
@@ -177,13 +179,17 @@ public void onError(BleError error) {
     }
 
     private void stopDeviceScan(Result result) {
-        bleAdapter.stopDeviceScan();
+        if (bleAdapter != null) {
+            bleAdapter.stopDeviceScan();
+        }
         scanningStreamHandler.onComplete();
         result.success(null);
     }
 
     private void cancelTransaction(MethodCall call, Result result) {
-        bleAdapter.cancelTransaction(call.<String>argument(ArgumentKey.TRANSACTION_ID));
+        if (bleAdapter != null) {
+            bleAdapter.cancelTransaction(call.<String>argument(ArgumentKey.TRANSACTION_ID));
+        }
         result.success(null);
     }
 }

example/lib/device_details/device_detail_view.dart

@@ -13,8 +13,8 @@ class DeviceDetailsView extends StatefulWidget {
 }
 
 class DeviceDetailsViewState extends State<DeviceDetailsView> {
-  DeviceDetailsBloc _deviceDetailsBloc;
-  StreamSubscription _appStateSubscription;
+  DeviceDetailsBloc? _deviceDetailsBloc;
+  StreamSubscription? _appStateSubscription;
 
   bool _shouldRunOnResume = true;
 
@@ -33,9 +33,9 @@ class DeviceDetailsViewState extends State<DeviceDetailsView> {
 
   void _onResume() {
     Fimber.d("onResume");
-    _deviceDetailsBloc.init();
+    _deviceDetailsBloc?.init();
     _appStateSubscription =
-        _deviceDetailsBloc.disconnectedDevice.listen((bleDevice) async {
+        _deviceDetailsBloc?.disconnectedDevice.listen((bleDevice) async {
       Fimber.d("navigate to details");
       _onPause();
       Navigator.pop(context);
@@ -46,8 +46,8 @@ class DeviceDetailsViewState extends State<DeviceDetailsView> {
 
   void _onPause() {
     Fimber.d("onPause");
-    _appStateSubscription.cancel();
-    _deviceDetailsBloc.dispose();
+    _appStateSubscription?.cancel();
+    _deviceDetailsBloc?.dispose();
   }
 
   @override
@@ -59,9 +59,13 @@ class DeviceDetailsViewState extends State<DeviceDetailsView> {
 
   @override
   Widget build(BuildContext context) {
+    final deviceDetailsBloc = _deviceDetailsBloc;
     return WillPopScope(
       onWillPop: () {
-        return _deviceDetailsBloc.disconnect().then((_) {
+        if (deviceDetailsBloc == null) {
+          return Future<bool>.value(true);
+        }
+        return deviceDetailsBloc.disconnect().then((_) {
           return false;
         });
       },
@@ -86,8 +90,10 @@ class DeviceDetailsViewState extends State<DeviceDetailsView> {
             ),
             body: TabBarView(
               children: <Widget>[
-                AutoTestView(_deviceDetailsBloc),
-                ManualTestView(_deviceDetailsBloc),
+                if (deviceDetailsBloc != null)
+                  AutoTestView(deviceDetailsBloc),
+                if (deviceDetailsBloc != null)
+                  ManualTestView(deviceDetailsBloc),
               ],
             )),
       ),