Emit button pressed event for buttons bound to external components

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/externalcomponent/ExternalComponentViewController.java

@@ -4,8 +4,10 @@ import android.app.Activity;
 import android.support.v4.app.FragmentActivity;
 
 import com.facebook.react.ReactInstanceManager;
+import com.facebook.react.bridge.ReactContext;
 import com.reactnativenavigation.parse.ExternalComponent;
 import com.reactnativenavigation.parse.Options;
+import com.reactnativenavigation.react.EventEmitter;
 import com.reactnativenavigation.viewcontrollers.NoOpYellowBoxDelegate;
 import com.reactnativenavigation.viewcontrollers.ViewController;
 import com.reactnativenavigation.views.ExternalComponentLayout;
@@ -31,7 +33,10 @@ public class ExternalComponentViewController extends ViewController<ExternalComp
 
     @Override
     public void sendOnNavigationButtonPressed(String buttonId) {
-
+        ReactContext currentReactContext = reactInstanceManager.getCurrentReactContext();
+        if (currentReactContext != null) {
+            new EventEmitter(currentReactContext).emitOnNavigationButtonPressed(getId(), buttonId);
+        }
     }
 
     public FragmentActivity getActivity() {