Add back button before view is created

This prevents the back button from being added too early when pushing screens.
If the back button is added before the actual push (current behaviour) the the previous screen's
title moves unexpectedly to make space for the back button.

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

@@ -101,7 +101,7 @@ public abstract class ViewController<T extends ViewGroup> implements ViewTreeObs
     @CallSuper
     public void mergeOptions(Options options) {
         this.options = this.options.mergeWith(options);
-        applyOptions(this.options);
+        if (view != null) applyOptions(this.options);
         this.options.clearOneTimeOptions();
     }
 

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/stack/BackButtonHelper.java

@@ -5,8 +5,8 @@ import com.reactnativenavigation.parse.params.Bool;
 import com.reactnativenavigation.viewcontrollers.ViewController;
 
 public class BackButtonHelper {
-    public void addToPushedChild(StackController stack, ViewController child) {
-        if (stack.size() <= 1 || child.options.topBar.buttons.left != null || child.options.topBar.buttons.back.visible.isFalse()) return;
+    public void addToPushedChild(ViewController child) {
+        if (child.options.topBar.buttons.left != null || child.options.topBar.buttons.back.visible.isFalse()) return;
         Options options = new Options();
         options.topBar.buttons.back.setVisible();
         child.mergeOptions(options);

lib/android/app/src/main/java/com/reactnativenavigation/viewcontrollers/stack/StackController.java

@@ -129,9 +129,9 @@ public class StackController extends ParentController<StackLayout> {
 
     public void push(ViewController child, CommandListener listener) {
         final ViewController toRemove = stack.peek();
+        backButtonHelper.addToPushedChild(child);
         child.setParentController(this);
         stack.push(child.getId(), child);
-        backButtonHelper.addToPushedChild(this, child);
         Options resolvedOptions = resolveCurrentOptions(presenter.getDefaultOptions());
         addChildToStack(child, child.getView(), resolvedOptions);
 

lib/android/app/src/test/java/com/reactnativenavigation/viewcontrollers/stack/BackButtonHelperTest.java

@@ -41,9 +41,9 @@ public class BackButtonHelperTest extends BaseTest {
     }
 
     @Test
-    public void addToChild_doesNotAddIfStackContainsOneChild() {
-        uut.addToPushedChild(stack, child1);
-        verify(child1, times(0)).mergeOptions(any());
+    public void addToChild() {
+        uut.addToPushedChild(child1);
+        verify(child1).mergeOptions(any());
     }
 
     @Test

lib/android/app/src/test/java/com/reactnativenavigation/viewcontrollers/stack/StackControllerTest.java

@@ -38,6 +38,7 @@ import org.assertj.core.api.iterable.Extractor;
 import org.json.JSONObject;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
+import org.mockito.InOrder;
 import org.mockito.Mockito;
 
 import java.util.ArrayList;
@@ -48,6 +49,7 @@ import java.util.List;
 import static org.assertj.core.api.Java6Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
@@ -65,11 +67,13 @@ public class StackControllerTest extends BaseTest {
     private NavigationAnimator animator;
     private TopBarController topBarController;
     private StackOptionsPresenter presenter;
+    private BackButtonHelper backButtonHelper;
 
     @Override
     public void beforeEach() {
         super.beforeEach();
         animator = Mockito.mock(NavigationAnimator.class);
+        backButtonHelper = spy(new BackButtonHelper());
         activity = newActivity();
         childRegistry = new ChildControllersRegistry();
         presenter = spy(new StackOptionsPresenter(activity, new TitleBarReactViewCreatorMock(), new Options()));
@@ -121,18 +125,6 @@ public class StackControllerTest extends BaseTest {
         verify(listener, times(1)).onSuccess(child1.getId());
     }
 
-    @Test
-    public void push_backButtonIsAddedIfStackContainsMoreThenOneScreen() {
-        uut.push(child1, new CommandListenerAdapter());
-        verify(child1, times(0)).mergeOptions(any());
-        assertThat(child1.options.topBar.buttons.back.visible.isFalseOrUndefined()).isTrue();
-
-        uut.push(child2, new CommandListenerAdapter());
-        ArgumentCaptor<Options> captor = ArgumentCaptor.forClass(Options.class);
-        verify(child2, times(1)).mergeOptions(captor.capture());
-        assertThat(captor.getValue().topBar.buttons.back.visible.get()).isTrue();
-    }
-
     @Test
     public void push_backButtonIsNotAddedIfScreenContainsLeftButton() {
         disablePushAnimation(child1, child2);
@@ -157,6 +149,18 @@ public class StackControllerTest extends BaseTest {
         verify(child1, times(0)).mergeOptions(any());
     }
 
+    @Test
+    public void push_backButtonAddedBeforeChildViewIsCreated() {
+        disablePopAnimation(child1, child2);
+        uut.push(child1, new CommandListenerAdapter());
+        uut.push(child2, new CommandListenerAdapter());
+
+        InOrder inOrder = inOrder(backButtonHelper, child2);
+        inOrder.verify(backButtonHelper).addToPushedChild(child2);
+        inOrder.verify(child2).setParentController(uut);
+        inOrder.verify(child2).getView(); // creates view
+    }
+
     @Test
     public void push_waitForRender() {
         disablePushAnimation(child1);
@@ -845,6 +849,7 @@ public class StackControllerTest extends BaseTest {
                 .setChildRegistry(childRegistry)
                 .setAnimator(animator)
                 .setStackPresenter(presenter)
+                .setBackButtonHelper(backButtonHelper)
                 .build();
     }