Navigator.push and pop in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens after Navigator.push is called?

In a Flutter app, when you call Navigator.push(context, MaterialPageRoute(builder: (context) => NewPage())), what is the immediate visible effect on the app UI?

Flutter

Navigator.push(context, MaterialPageRoute(builder: (context) => NewPage()));

A The app crashes because Navigator.push requires a pop before pushing.

B The app navigates to NewPage and displays its UI on top of the current page.

C The app reloads the current page without any navigation.

D The app closes the current page and returns to the previous page.

💡 Hint

Think about what 'push' means in navigation stacks.

Navigator.push adds a new page on top of the current stack, so the new page appears on screen.

❓ ui_behavior

intermediate

What is the effect of Navigator.pop(context)?

In Flutter, what happens when Navigator.pop(context) is called on a page that was pushed onto the stack?

Flutter

Navigator.pop(context);

A The current page is removed and the previous page becomes visible.

B The app closes completely.

C A new page is pushed on top of the current page.

D Nothing happens because pop requires a parameter.

💡 Hint

Pop means to remove the top page from the stack.

Navigator.pop removes the current route, revealing the one below it.

❓ lifecycle

advanced

What lifecycle method is called when a page is popped?

When you call Navigator.pop(context) to close a page in Flutter, which lifecycle method of the popped page is called just before it disappears?

A build()

B initState()

C dispose()

D didChangeDependencies()

💡 Hint

Think about cleaning up resources when a widget is removed.

dispose() is called when a StatefulWidget is removed from the widget tree, such as when popped.

❓ navigation

advanced

What is the result of this Navigator.push call with await?

Consider this Flutter code snippet: final result = await Navigator.push(context, MaterialPageRoute(builder: (context) => InputPage())); What does the variable 'result' contain after the pushed page is popped?

Flutter

final result = await Navigator.push(context, MaterialPageRoute(builder: (context) => InputPage()));

A The value passed to Navigator.pop(context, value) from InputPage.

B Always null because Navigator.push does not return a value.

C The current context object.

D An error because Navigator.push cannot be awaited.

💡 Hint

Navigator.push returns a Future that completes when the page is popped.

Navigator.push returns a Future that resolves to the value passed to pop on the pushed page.

🔧 Debug

expert

Why does this Navigator.pop call cause an error?

Given this Flutter code inside a widget: Navigator.pop(); Why might this cause a runtime error?

A Because Navigator.pop cannot be called inside a widget.

B Because Navigator.pop only works if there is more than one page in the stack.

C Because Navigator.pop requires a route name as a parameter.

D Because Navigator.pop requires a BuildContext parameter to know which navigator to pop.

💡 Hint

Navigator methods usually need context to find the right navigator.

Navigator.pop requires the BuildContext to find the Navigator in the widget tree to pop the current route.