navigator pop

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

 
 	@Override
 	public Collection<ViewController> getChildControllers() {
-		return Collections.singletonList(root);
+		return root == null ? Collections.<ViewController>emptyList() : Collections.singletonList(root);
 	}
 
 	/*
 		getView().addView(viewController.getView());
 	}
 
-	public void push(final String onId, final ViewController viewController) {
-		ViewController found = root.findControllerById(onId);
+	public void push(final String fromId, final ViewController viewController) {
+		ViewController found = findControllerById(fromId);
 		if (found == null) return;
 
 		StackController parentStackController = found.getParentStackController();
 
 		parentStackController.push(viewController);
 	}
+
+	public void pop(final String fromId) {
+		ViewController found = findControllerById(fromId);
+		if (found == null) return;
+
+		StackController parentStackController = found.getParentStackController();
+		if (parentStackController == null) return;
+
+		parentStackController.pop();
+	}
 }

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

 	private Navigator uut;
 	private ViewController child1;
 	private ViewController child2;
+	private ViewController child3;
 
 	@Override
 	public void beforeEach() {
 		uut = new Navigator(activity);
 		child1 = new SimpleViewController(activity, "child1");
 		child2 = new SimpleViewController(activity, "child2");
+		child3 = new SimpleViewController(activity, "child3");
 	}
 
 
 		stack1.push(child1);
 		stack2.push(child2);
 		bottomTabsController.setTabs(Arrays.<ViewController>asList(stack1, stack2));
-
 		uut.setRoot(bottomTabsController);
+
 		SimpleViewController newChild = new SimpleViewController(activity, "new child");
 		uut.push(child2.getId(), newChild);
 
 		assertThat(stack2.getChildControllers()).contains(newChild);
 	}
 
+	@Test
+	public void pop_InvalidDoesNothing() throws Exception {
+		uut.pop("123");
+		uut.setRoot(child1);
+		uut.pop(child1.getId());
+	}
+
+	@Test
+	public void pop_FromCorrectStackByFindingChildId() throws Exception {
+		BottomTabsController bottomTabsController = new BottomTabsController(activity, "tabsController");
+		StackController stack1 = new StackController(activity, "stack1");
+		StackController stack2 = new StackController(activity, "stack2");
+		stack1.push(child1);
+		stack2.push(child2);
+		stack2.push(child3);
+		bottomTabsController.setTabs(Arrays.<ViewController>asList(stack1, stack2));
+		uut.setRoot(bottomTabsController);
+
+		uut.pop(child2.getId());
+
+		assertThat(stack2.getChildControllers()).containsOnly(child2);
+	}
+
 	private void assertHasSingleChildViewOf(ViewController parent, ViewController child) {
 		assertThat(((ViewGroup) parent.getView()).getChildCount()).isEqualTo(1);
 		assertThat(((ViewGroup) parent.getView()).getChildAt(0)).isEqualTo(child.getView()).isNotNull();