navigator setContentView

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/Navigator.java

 package com.reactnativenavigation.viewcontrollers;
 
 import android.app.Activity;
+import android.support.annotation.NonNull;
 import android.view.View;
 import android.widget.FrameLayout;
 
 		super(activity);
 	}
 
+	@NonNull
 	@Override
 	protected View createView() {
 		FrameLayout view = new FrameLayout(getActivity());

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/ViewController.java

 package com.reactnativenavigation.viewcontrollers;
 
 import android.app.Activity;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.view.View;
 
 		this.activity = activity;
 	}
 
+	@NonNull
 	protected abstract View createView();
 
 	public boolean handleBack() {
 		this.stackController = stackController;
 	}
 
+	@NonNull
 	public View getView() {
 		if (view == null) {
 			view = createView();

lib/android/app/src/test/java/com/reactnativenavigation/viewcontrollers/NavigatorTest.java

 	public void setsItselfAsContentView() throws Exception {
 		assertThat(Shadows.shadowOf(activity).getContentView()).isNull();
 		uut.onActivityCreated();
-		assertThat(Shadows.shadowOf(activity).getContentView()).isEqualTo(uut.getView());
-
+		assertThat(Shadows.shadowOf(activity).getContentView()).isNotNull().isEqualTo(uut.getView());
 	}
 }