Add user state observer

Author: jennantilla

android/src/main/java/com/onesignal/flutter/OneSignalSerializer.java

@@ -2,6 +2,8 @@
 
 import android.util.Log;
 
+import com.onesignal.user.state.UserChangedState;
+import com.onesignal.user.state.UserState;
 import com.onesignal.user.subscriptions.ISubscription;
 import com.onesignal.user.subscriptions.IPushSubscription;
 import com.onesignal.user.subscriptions.PushSubscriptionChangedState;
@@ -187,6 +189,18 @@ static HashMap<String, Object> convertPushSubscriptionState(PushSubscriptionStat
         return hash;
     }
 
+    static HashMap<String, Object> convertUserState(UserState state) throws JSONException {
+        HashMap<String, Object> hash = new HashMap<>();
+    
+        String onesignalId = setNullIfEmpty(state.getOnesignalId());
+        String externalId = setNullIfEmpty(state.getExternalId());
+    
+        hash.put("onesignalId", onesignalId);
+        hash.put("externalId", externalId);
+    
+        return hash;
+    }
+
     static HashMap<String, Object> convertOnPushSubscriptionChange(PushSubscriptionChangedState changedState) throws JSONException {
         HashMap<String, Object> hash = new HashMap<>();
 
@@ -197,6 +211,14 @@ static HashMap<String, Object> convertOnPushSubscriptionChange(PushSubscriptionC
         return hash;
     }
 
+    static HashMap<String, Object> convertOnUserStateChange(UserChangedState changedState) throws JSONException {
+        HashMap<String, Object> hash = new HashMap<>();
+
+        
+        hash.put("current", convertUserState(changedState.getCurrent()));
+    
+        return hash;
+    }
 
     static HashMap<String, Object> convertJSONObjectToHashMap(JSONObject object) throws JSONException {
         HashMap<String, Object> hash = new HashMap<>();
@@ -242,4 +264,9 @@ else if (val instanceof JSONObject)
 
         return list;
     }
+
+    /** Helper method to return null value if string is empty **/
+    static String setNullIfEmpty(String value) {
+        return value.isEmpty() ? null : value;
+    }
 }

android/src/main/java/com/onesignal/flutter/OneSignalUser.java

@@ -2,6 +2,9 @@
 
 import com.onesignal.OneSignal;
 import com.onesignal.debug.LogLevel;
+import com.onesignal.debug.internal.logging.Logging;
+import com.onesignal.user.state.IUserStateObserver;
+import com.onesignal.user.state.UserChangedState;
 
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -18,8 +21,7 @@
 import io.flutter.plugin.common.PluginRegistry;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
 
-public class OneSignalUser extends FlutterRegistrarResponder implements MethodCallHandler {
-    private MethodChannel channel;
+public class OneSignalUser extends FlutterRegistrarResponder implements MethodCallHandler, IUserStateObserver {
 
     static void registerWith(BinaryMessenger messenger) {
         OneSignalUser controller = new OneSignalUser();
@@ -54,6 +56,8 @@ else if (call.method.contentEquals("OneSignal#removeTags"))
             this.removeTags(call, result);
         else if (call.method.contentEquals("OneSignal#getTags"))
             this.getTags(call, result);
+        else if (call.method.contentEquals("OneSignal#lifecycleInit"))
+            this.lifecycleInit();
         else
             replyNotImplemented(result);
     }
@@ -67,6 +71,10 @@ private void setLanguage(MethodCall call, Result result) {
         replySuccess(result, null);
     }
 
+    private void lifecycleInit() {
+        OneSignal.getUser().addObserver(this);
+    }
+
     private void getOnesignalId(MethodCall call, Result result) {
         String onesignalId = OneSignal.getUser().getOnesignalId();
         if (onesignalId.isEmpty()) {
@@ -150,4 +158,14 @@ private void removeTags(MethodCall call, Result result) {
     private void getTags(MethodCall call, Result result) {
         replySuccess(result, OneSignal.getUser().getTags());
     }
+
+    @Override
+    public void onUserStateChange(UserChangedState userChangedState) {
+        try {
+            invokeMethodOnUiThread("OneSignal#onUserStateChange", OneSignalSerializer.convertOnUserStateChange(userChangedState));
+        } catch (JSONException e) {
+            e.getStackTrace();
+            Logging.error("Encountered an error attempting to convert UserChangedState object to hash map:" + e.toString(), null);
+        }
+    }
 }

ios/Classes/OSFlutterUser.m

@@ -69,7 +69,8 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
         [self addSms:call withResult:result];
     else if ([@"OneSignal#removeSms" isEqualToString:call.method])
         [self removeSms:call withResult:result];
-    
+    else if ([@"OneSignal#lifecycleInit" isEqualToString:call.method])
+        [self lifecycleInit:call withResult:result];
     else
         result(FlutterMethodNotImplemented);
 }
@@ -136,11 +137,41 @@ - (void)removeSms:(FlutterMethodCall *)call withResult:(FlutterResult)result {
     result(nil);
 }
 
+- (void)lifecycleInit:(FlutterMethodCall *)call withResult:(FlutterResult)result {
+    [OneSignal.User addObserver:self];
+    result(nil);
+}
+
+- (void)onUserStateDidChangeWithState:(OSUserChangedState *)state {
+    NSString *onesignalId = [self getStringOrNSNull:state.current.onesignalId];
+    NSString *externalId = [self getStringOrNSNull:state.current.externalId];
+
+    NSMutableDictionary *result = [NSMutableDictionary new];
+    
+    NSMutableDictionary *currentObject = [NSMutableDictionary new];
+    
+    currentObject[@"onesignalId"] = onesignalId;
+    currentObject[@"externalId"] = externalId;
+    result[@"current"] = currentObject;
+
+    [self.channel invokeMethod:@"OneSignal#onUserStateChange" arguments:result];
+}
+
 - (void)getOnesignalId:(FlutterMethodCall *)call withResult:(FlutterResult)result {
     result(OneSignal.User.onesignalId);
 }
 
 - (void)getExternalId:(FlutterMethodCall *)call withResult:(FlutterResult)result {
     result(OneSignal.User.externalId);
 }
+
+/** Helper method to return NSNull if string is empty or nil **/
+- (NSString *)getStringOrNSNull:(NSString *)string {
+    // length method can be used on nil and strings
+    if (string.length > 0) {
+        return string;
+    } else {
+        return [NSNull null];
+    }
+}
 @end

lib/onesignal_flutter.dart

@@ -48,6 +48,7 @@ class OneSignal {
   static void initialize(String appId) {
     _channel.invokeMethod('OneSignal#initialize', {'appId': appId});
     InAppMessages.lifecycleInit();
+    User.lifecycleInit();
     User.pushSubscription.lifecycleInit();
     Notifications.lifecycleInit();
   }

lib/src/user.dart

@@ -1,8 +1,45 @@
 import 'dart:async';
 import 'package:flutter/services.dart';
 
+import 'package:onesignal_flutter/src/utils.dart';
 import 'package:onesignal_flutter/src/pushsubscription.dart';
 
+typedef void OnUserChangeObserver(OSUserChangedState stateChanges);
+
+/// Represents the current user state with OneSignal.
+class OSUserState extends JSONStringRepresentable {
+  String? onesignalId;
+  String? externalId;
+
+  OSUserState(Map<String, dynamic> json) {
+    if (json.containsKey('onesignalId'))
+      this.onesignalId = json['onesignalId'] as String?;
+    if (json.containsKey('externalId'))
+      this.externalId = json['externalId'] as String?;
+  }
+
+  String jsonRepresentation() {
+    return convertToJsonString(
+        {'onesignalId': this.onesignalId, 'externalId': this.externalId});
+  }
+}
+
+/// An instance of this class describes a change in the user state.
+class OSUserChangedState extends JSONStringRepresentable {
+  late OSUserState current;
+
+  OSUserChangedState(Map<String, dynamic> json) {
+    if (json.containsKey('current'))
+      this.current = OSUserState(json['current'].cast<String, dynamic>());
+  }
+
+  String jsonRepresentation() {
+    return convertToJsonString(<String, dynamic>{
+      'current': current.jsonRepresentation(),
+    });
+  }
+}
+
 class OneSignalUser {
   static OneSignalPushSubscription _pushSubscription =
       new OneSignalPushSubscription();
@@ -12,6 +49,12 @@ class OneSignalUser {
   // private channels used to bridge to ObjC/Java
   MethodChannel _channel = const MethodChannel('OneSignal#user');
 
+  List<OnUserChangeObserver> _observers = <OnUserChangeObserver>[];
+  // constructor method
+  OneSignalUser() {
+    this._channel.setMethodCallHandler(_handleMethod);
+  }
+
   /// Sets the user's language.
   ///
   /// Sets the user's language to [language] this also applies to
@@ -125,4 +168,35 @@ class OneSignalUser {
         await _channel.invokeMethod("OneSignal#getOnesignalId");
     return onesignalId;
   }
+
+  /// Add an observer that fires when the OneSignal User state changes.
+  /// *Important* When using the observer to retrieve the onesignalId, check the
+  /// externalId as well to confirm the values are associated with the expected user.*
+  void addObserver(OnUserChangeObserver observer) {
+    _observers.add(observer);
+  }
+
+  // Remove a user state observer that has been previously added.
+  void removeObserver(OnUserChangeObserver observer) {
+    _observers.remove(observer);
+  }
+
+  Future<void> lifecycleInit() async {
+    return await _channel.invokeMethod("OneSignal#lifecycleInit");
+  }
+
+  // Private function that gets called by ObjC/Java
+  Future<Null> _handleMethod(MethodCall call) async {
+    if (call.method == 'OneSignal#onUserStateChange') {
+      this._onUserStateChange(
+          OSUserChangedState(call.arguments.cast<String, dynamic>()));
+    }
+    return null;
+  }
+
+  void _onUserStateChange(OSUserChangedState stateChanges) async {
+    for (var observer in _observers) {
+      observer(stateChanges);
+    }
+  }
 }