[Feature] iOS: initial support for Restore State

README.md

@@ -598,7 +598,11 @@ Add the following to your `Info.plist`
 
 When this key-value pair is included in the app’s Info.plist file, the system wakes up your app to process ble `read`, `write`, and `subscription` events.
 
-You may also have to use https://pub.dev/packages/workmanager
+To wake up your app even after it is killed by the OS, set the `restoreIosState` option to true **before** starting any FBP work**:
+
+```
+FlutterBluePlus.setOptions(restoreIosState: true);
+```
 
 **Note**: Upon being woken up, an app has around 10 seconds to complete a task. Apps that spend too much time executing in the background can be throttled back by the system or killed.
 

ios/Classes/FlutterBluePlusPlugin.m

@@ -54,6 +54,7 @@ @interface FlutterBluePlusPlugin ()
 @property(nonatomic) NSTimer *checkForMtuChangesTimer;
 @property(nonatomic) LogLevel logLevel;
 @property(nonatomic) NSNumber *showPowerAlert;
+@property(nonatomic) NSNumber *restoreState;
 @end
 
 @implementation FlutterBluePlusPlugin
@@ -75,6 +76,7 @@ + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar
     instance.scanCounts = [NSMutableDictionary new];
     instance.logLevel = LDEBUG;
     instance.showPowerAlert = @(YES);
+    instance.restoreState = @(NO);
 
     [registrar addMethodCallDelegate:instance channel:methodChannel];
 }
@@ -104,10 +106,19 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
     {
         Log(LDEBUG, @"handleMethodCall: %@", call.method);
 
+        if ([@"setLogLevel" isEqualToString:call.method])
+        {
+            NSNumber *idx = [call arguments];
+            self.logLevel = (LogLevel)[idx integerValue];
+            result(@YES);
+            return;
+        }
+
         if ([@"setOptions" isEqualToString:call.method])
         {
             NSDictionary *args = (NSDictionary*) call.arguments;
             self.showPowerAlert = args[@"show_power_alert"];
+            self.restoreState = args[@"restore_state"];
             result(@YES);
             return;
         }
@@ -117,11 +128,18 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
         {
             Log(LDEBUG, @"initializing CBCentralManager");
 
-            NSDictionary *options = @{
-                CBCentralManagerOptionShowPowerAlertKey: self.showPowerAlert
-            };
+            NSMutableDictionary *options = [NSMutableDictionary dictionary];
 
-            Log(LDEBUG, @"show power alert: %@", [self.showPowerAlert boolValue] ? @"yes" : @"no");
+            if ([self.showPowerAlert boolValue]) {
+                options[CBCentralManagerOptionShowPowerAlertKey] = self.showPowerAlert;
+            }
+
+            if ([self.restoreState boolValue]) {
+                options[CBCentralManagerOptionRestoreIdentifierKey] = @"flutterBluePlusRestoreIdentifier";
+            }
+
+            Log(LDEBUG, @"showPowerAlert: %@", [self.showPowerAlert boolValue] ? @"yes" : @"no");
+            Log(LDEBUG, @"restoreState: %@", [self.restoreState boolValue] ? @"yes" : @"no");
 
             self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil options:options];
         }
@@ -185,13 +203,6 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result
             result(@(self.connectedPeripherals.count));
             return;
         }
-        else if ([@"setLogLevel" isEqualToString:call.method])
-        {
-            NSNumber *idx = [call arguments];
-            self.logLevel = (LogLevel)[idx integerValue];
-            result(@YES);
-            return;
-        }
         else if ([@"isSupported" isEqualToString:call.method])
         {
             result(self.centralManager != nil ? @(YES) : @(NO));
@@ -1026,6 +1037,46 @@ - (void)checkForMtuChangesCallback
 // ██   ██  ██       ██       ██       ██    ██  ██   ██     ██     ██               
 // ██████   ███████  ███████  ███████   ██████   ██   ██     ██     ███████ 
 
+- (void)centralManager:(CBCentralManager *)central
+      willRestoreState:(NSDictionary *)state {
+
+    // restore adapter state
+    [self centralManagerDidUpdateState:central];
+
+    NSArray *peripherals = state[CBCentralManagerRestoredStatePeripheralsKey];
+
+    for (CBPeripheral *peripheral in peripherals) {
+
+        // Set the delegate to self to receive the peripheral callbacks
+        peripheral.delegate = self;
+
+        // skip if not connected
+        if (peripheral.state != CBPeripheralStateConnected) {
+            continue;
+        }
+
+        // update connection state
+        [self centralManager:central didConnectPeripheral:peripheral];
+
+        for (CBService *service in peripheral.services) {
+
+            // restore services
+            [self peripheral:peripheral didDiscoverServices:nil];
+
+            for (CBCharacteristic *characteristic in service.characteristics) {
+
+                // restore characteristics
+                [self peripheral:peripheral didDiscoverCharacteristicsForService:service error:nil];
+
+                // restore notidications
+                if (characteristic.isNotifying) {
+                    [self peripheral:peripheral didUpdateNotificationStateForCharacteristic:characteristic error:nil];
+                }
+            }
+        }
+    }
+}
+
 - (void)centralManagerDidUpdateState:(nonnull CBCentralManager *)central
 {
     Log(LDEBUG, @"centralManagerDidUpdateState %@", [self cbManagerStateString:self.centralManager.state]);

lib/src/flutter_blue_plus.dart

@@ -105,10 +105,14 @@ class FlutterBluePlus {
   ///       To set this option you must call this method before any other method in this package.
   ///       See: https://developer.apple.com/documentation/corebluetooth/cbcentralmanageroptionshowpoweralertkey
   ///       This option has no effect on Android.
+  ///   - [restoreState] Whether to opt into state restoration (iOS & MacOS only). i.e. CBCentralManagerOptionRestoreIdentifierKey
+  ///       To set this option you must call this method before any other method in this package.
+  ///       See Apple Documentation for more details. This option has no effect on Android.    
   static Future<void> setOptions({
     bool showPowerAlert = true,
+    bool restoreState = false,
   }) async {
-    await _invokeMethod('setOptions', {"show_power_alert": showPowerAlert});
+    await _invokeMethod('setOptions', {"show_power_alert": showPowerAlert, "restore_state": restoreState});
   }
 
   /// Turn on Bluetooth (Android only),
@@ -592,7 +596,7 @@ class FlutterBluePlus {
 
     try {
       // initialize
-      if (method != "setOptions") {
+      if (method != "setOptions" && method != "setLogLevel") {
         _initFlutterBluePlus();
       }