fix crash with WorkManager helper for initialization

* Before using WorkManager, check for its existence. Else, in rare cases that were crashing, initialize it ourselves.
* Provides a method to check if WorkManager is initialized in this process.
  - This is effectively the `WorkManager.isInitialized()` public method introduced in `androidx.work:work-*:2.8.0-alpha02`.
  - Please see https://android-review.googlesource.com/c/platform/frameworks/support/+/1941186 for the library's implementation

* Please see issue this aims to address: #1672

OneSignalSDK/onesignal/src/main/java/com/onesignal/OSFocusHandler.kt

@@ -32,7 +32,6 @@ import androidx.work.Constraints
 import androidx.work.ExistingWorkPolicy
 import androidx.work.NetworkType
 import androidx.work.OneTimeWorkRequest
-import androidx.work.WorkManager
 import androidx.work.Worker
 import androidx.work.WorkerParameters
 import java.util.concurrent.TimeUnit
@@ -87,7 +86,8 @@ class OSFocusHandler {
             .setInitialDelay(delay, TimeUnit.MILLISECONDS)
             .addTag(tag)
             .build()
-        WorkManager.getInstance(context)
+
+        OSWorkManagerHelper.getInstance(context)
             .enqueueUniqueWork(
                 tag,
                 ExistingWorkPolicy.KEEP,
@@ -96,7 +96,7 @@ class OSFocusHandler {
     }
 
     fun cancelOnLostFocusWorker(tag: String, context: Context) {
-        WorkManager.getInstance(context).cancelAllWorkByTag(tag)
+        OSWorkManagerHelper.getInstance(context).cancelAllWorkByTag(tag)
     }
 
     private fun resetStopState() {

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

@@ -9,7 +9,6 @@
 import androidx.annotation.NonNull;
 import androidx.work.ExistingWorkPolicy;
 import androidx.work.OneTimeWorkRequest;
-import androidx.work.WorkManager;
 import androidx.work.Worker;
 import androidx.work.WorkerParameters;
 
@@ -45,7 +44,7 @@ public static void beginEnqueueingWork(Context context, boolean shouldDelay) {
                 .setInitialDelay(restoreDelayInSeconds, TimeUnit.SECONDS)
                 .build();
 
-        WorkManager.getInstance(context)
+        OSWorkManagerHelper.getInstance(context)
                 .enqueueUniqueWork(NOTIFICATION_RESTORE_WORKER_IDENTIFIER, ExistingWorkPolicy.KEEP, workRequest);
     }
 

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

@@ -6,7 +6,6 @@
 import androidx.work.Data;
 import androidx.work.ExistingWorkPolicy;
 import androidx.work.OneTimeWorkRequest;
-import androidx.work.WorkManager;
 import androidx.work.Worker;
 import androidx.work.WorkerParameters;
 
@@ -63,8 +62,9 @@ static void beginEnqueueingWork(Context context, String osNotificationId, int an
                 .build();
 
         OneSignal.Log(OneSignal.LOG_LEVEL.DEBUG, "OSNotificationWorkManager enqueueing notification work with notificationId: " + osNotificationId + " and jsonPayload: " + jsonPayload);
-        WorkManager.getInstance(context)
-                .enqueueUniqueWork(osNotificationId, ExistingWorkPolicy.KEEP, workRequest);
+
+        OSWorkManagerHelper.getInstance(context).
+                enqueueUniqueWork(osNotificationId, ExistingWorkPolicy.KEEP, workRequest);
     }
 
     public static class NotificationWorker extends Worker {

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

@@ -35,7 +35,6 @@
 import androidx.work.ExistingWorkPolicy;
 import androidx.work.NetworkType;
 import androidx.work.OneTimeWorkRequest;
-import androidx.work.WorkManager;
 import androidx.work.Worker;
 import androidx.work.WorkerParameters;
 
@@ -82,7 +81,7 @@ void beginEnqueueingWork(Context context, String osNotificationId) {
 
         OneSignal.Log(OneSignal.LOG_LEVEL.DEBUG, "OSReceiveReceiptController enqueueing send receive receipt work with notificationId: " + osNotificationId + " and delay: " + delay + " seconds");
 
-        WorkManager.getInstance(context)
+        OSWorkManagerHelper.getInstance(context)
                 .enqueueUniqueWork(osNotificationId + "_receive_receipt", ExistingWorkPolicy.KEEP, workRequest);
     }
 

OneSignalSDK/onesignal/src/main/java/com/onesignal/OSWorkManagerHelper.kt

@@ -0,0 +1,68 @@
+/**
+ * Modified MIT License
+ * <p>
+ * Copyright 2023 OneSignal
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * 1. The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 2. All copies of substantial portions of the Software may only be used in connection
+ * with services provided by OneSignal.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.onesignal
+
+import android.annotation.SuppressLint
+import android.content.Context
+import androidx.work.Configuration
+import androidx.work.WorkManager
+import androidx.work.impl.WorkManagerImpl
+
+object OSWorkManagerHelper {
+    /**
+     * Helper method to provide a way to check if WorkManager is initialized in this process.
+     *
+     * This is effectively the `WorkManager.isInitialized()` public method introduced in androidx.work:work-*:2.8.0-alpha02.
+     * Please see https://android-review.googlesource.com/c/platform/frameworks/support/+/1941186.
+     *
+     * @return `true` if WorkManager has been initialized in this process.
+     */
+    @SuppressWarnings("deprecation")
+    @SuppressLint("RestrictedApi")
+    private fun isInitialized(): Boolean {
+        val instance = WorkManagerImpl.getInstance()
+        return instance != null
+    }
+
+    /**
+     * If there is an instance of WorkManager available, use it. Else, in rare cases, initialize it ourselves.
+     *
+     * Calling `WorkManager.getInstance(context)` directly can cause an exception if it is null.
+     *
+     * @return an instance of WorkManager
+     */
+    @JvmStatic
+    fun getInstance(context: Context): WorkManager {
+        return if (isInitialized()) {
+            WorkManager.getInstance(context)
+        } else {
+            WorkManager.initialize(context, Configuration.Builder().build())
+            WorkManager.getInstance(context)
+        }
+    }
+}