title: The crash due to Facebook SDK 5.0 on Android 4.X
body: <p>Here is the crash log:</p>
  
  <pre><code>Fatal Exception: java.lang.AbstractMethodError
         at java.lang.reflect.Method.invokeNative(Method.java)
         at java.lang.reflect.Method.invoke(Method.java:515)
         at com.facebook.appevents.internal.InAppPurchaseEventManager.invokeMethod(InAppPurchaseEventManager.java:618)
         at com.facebook.appevents.internal.InAppPurchaseEventManager.isBillingSupported(InAppPurchaseEventManager.java:223)
         at com.facebook.appevents.internal.InAppPurchaseEventManager.getPurchases(InAppPurchaseEventManager.java:395)
         at com.facebook.appevents.internal.InAppPurchaseEventManager.getPurchasesInapp(InAppPurchaseEventManager.java:231)
         at com.facebook.appevents.internal.InAppPurchaseActivityLifecycleTracker$2$1.run(InAppPurchaseActivityLifecycleTracker.java:120)
         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
         at java.lang.Thread.run(Thread.java:841)
  </code></pre>
  
  <p>I only import <code>implementation 'com.facebook.android:facebook-login:5.0.0'</code> in gradle.build for Firebase Facebook Auth.</p>
  
  <p>Anyway I can let my app work with Android 4.X and also keep Facebook SDK for Auth? Thanks.</p>