Add Singleton LanguageContext and Dependency Injection to constructor

* Add Singleton pattern to LanguageContext class
* Add OSSharedPreference dependency to LanguageProviderAppDefined constructor
* Add OSSharedPreference dependency to LanguageContext constructor

Author: tanaynigam

OneSignalSDK/onesignal/src/main/java/com/onesignal/OneSignal.java

@@ -739,7 +739,7 @@ public static void init(Context context, String googleProjectNumber, String oneS
          mGoogleProjectNumber = googleProjectNumber;
 
       // Set Language Context to null
-      languageContext = new LanguageContext();
+      languageContext = new LanguageContext(preferences);
 
       subscribableStatus = osUtils.initializationChecker(context, oneSignalAppId);
       if (isSubscriptionStatusUninitializable())
@@ -1608,7 +1608,7 @@ public void run() {
          return;
       }
 
-      LanguageProviderAppDefined languageProviderAppDefined = new LanguageProviderAppDefined();
+      LanguageProviderAppDefined languageProviderAppDefined = new LanguageProviderAppDefined(preferences);
       languageProviderAppDefined.setLanguage(language);
       languageContext.setStrategy(languageProviderAppDefined);
    }

OneSignalSDK/onesignal/src/main/java/com/onesignal/language/LanguageContext.java

@@ -1,5 +1,5 @@
 package com.onesignal.language;
-import com.onesignal.OneSignal;
+import com.onesignal.OSSharedPreferences;
 import static com.onesignal.language.LanguageProviderAppDefined.PREFS_OS_LANGUAGE;
 
 /*
@@ -8,11 +8,17 @@
  */
 public class LanguageContext {
     private LanguageProvider strategy;
+    private static LanguageContext instance = null;
 
-    public LanguageContext() {
-        if ( OneSignal.preferences.getString(
-                OneSignal.preferences.getPreferencesName(), PREFS_OS_LANGUAGE, null) != null) {
-            this.strategy = new LanguageProviderAppDefined();
+    public static LanguageContext getInstance() {
+        return instance;
+    }
+
+    public LanguageContext(OSSharedPreferences preferences) {
+        instance = this;
+        if ( preferences.getString(
+                preferences.getPreferencesName(), PREFS_OS_LANGUAGE, null) != null) {
+            this.strategy = new LanguageProviderAppDefined(preferences);
         }
         else {
             this.strategy = new LanguageProviderDevice();

OneSignalSDK/onesignal/src/main/java/com/onesignal/language/LanguageProviderAppDefined.java

@@ -1,18 +1,23 @@
 package com.onesignal.language;
-import com.onesignal.OneSignal;
+import com.onesignal.OSSharedPreferences;
 
 public class LanguageProviderAppDefined implements LanguageProvider{
     public static final String PREFS_OS_LANGUAGE = "PREFS_OS_LANGUAGE";
+    private OSSharedPreferences preferences;
+
+    public LanguageProviderAppDefined(OSSharedPreferences preferences) {
+        this.preferences = preferences;
+    }
 
     public void setLanguage(String language) {
-        OneSignal.preferences.saveString(
-                OneSignal.preferences.getPreferencesName(),
+        preferences.saveString(
+                preferences.getPreferencesName(),
                 PREFS_OS_LANGUAGE,
                 language);
     }
 
     public String getLanguage() {
-        return OneSignal.preferences.getString(
-                OneSignal.preferences.getPreferencesName(), PREFS_OS_LANGUAGE, "en");
+        return preferences.getString(
+                preferences.getPreferencesName(), PREFS_OS_LANGUAGE, "en");
     }
 }