Using Navigator inside setState - flutter

Question

I have a list of Strings (called questions).
I create a Text widget based on the current string in the list.
I have an index int that increases every time a button is pressed.
I increase the current index by 1 in the setState method.
I need to navigate to a different page when the current index reaches the length of the String list.
Otherwise, I will get an RangeError naturally.
setState(() {
this.currentIndex++;
if(this.currentIndex == questions.length) {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => Loser()),
);
}
});
Now based on the code above, the error page appears and disappears quickly.
It is replaced by the Loser() page quickly.
Why is that?
And how can I navigate to the Loser() page without the error page showing?
Edit: As requested, the error message:
════════ Exception caught by widgets library ═══════════════════════════════════
The following RangeError was thrown building LandingPage(dirty, state: _LandingPageState#a8efe):
RangeError (index): Invalid value: Not in inclusive range 0..10: 11
The relevant error-causing widget was
LandingPage
lib/main.dart:21
When the exception was thrown, this was the stack
#0 List.[] (dart:core-patch/growable_array.dart:153:60)
#1 _LandingPageState.build
package:testing_http_package/landing_page.dart:88
#2 StatefulElement.build
package:flutter/…/widgets/framework.dart:4628
#3 ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4511
#4 StatefulElement.performRebuild
package:flutter/…/widgets/framework.dart:4684
...
════════════════════════════════════════════════════════════════════════════════
Edit: The widget I think in the build method that is causing the error:
child: Center(
child: Text(
questions[currentIndex], // This line
style: style,
textAlign: TextAlign.center,
),
),
),
Shouldn't the setState method go straight to the page before rerunning the build method?
Edit: I added the didChangeDependencies method as per #Nuts suggestion but it did not work. Now only the error page appears and it does not proceeds to the other page:
#override
void didChangeDependencies() {
WidgetsBinding.instance.addPostFrameCallback((_) {
if(this.currentIndex == questions.length) {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => Loser()),
);
}
});
super.didChangeDependencies();
}

Answer 1

With setState - you are rebuilding the whole widget and while doing it - navigating. So you are trying to rebuild widgets with invalid params (in your case index)
this.currentIndex++;
if(this.currentIndex => questions.length) {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => Loser()),
);
}
else setState(() {}); // if currentIndex is valid, just rebuild