Flutter - How to change index of BottomNavigationBar if NavigationBar is not visible? - flutter

Question

This is my setup:
Home.dart
final List<Widget> _pages = [
Screen1(),
Screen2(),
Screen3(),
Screen4(),
];
int _selectedPageIndex = 0;
void _selectPage(int index) {
setState(() {
_selectedPageIndex = index;
});}
#override
Widget build(BuildContext context) {
return Scaffold(
extendBodyBehindAppBar: true,
body: _pages[_selectedPageIndex],
bottomNavigationBar: _selectedPageIndex != 2
? Column(mainAxisSize: MainAxisSize.min, children: <Widget>[
...
Now when we navigate to Screen3() I'm hiding the complete BottomNavigationBar and show the Screen in Fullscreen. With a button I want to navigate back to any other position. How to do this? I don't want to use any Routes to close. How can we access _selectedPageIndex or do you have another good idea?
Would appreciate any ideas.

Answer 1

You can copy paste run full code below
Step 1: keep previous index, needed when go back from full screen page
void _onItemTapped(int index) {
setState(() {
_previousIndex = _selectedPageIndex;
_selectedPageIndex = index;
});
}
Step 2: pass refresh() callback to full screen page here is Setting()
void refresh() {
setState(() {
_selectedPageIndex = _previousIndex;
});
}
...
case 2:
{
print("settings");
return Settings(
callback: refresh,
);
}
Step 3: In full screen page's Raised Button call this callback
RaisedButton(
onPressed: () {
widget.callback();
},
child: Text("Go back"),
)
working demo
full code
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
/// This Widget is the main application widget.
class MyApp extends StatelessWidget {
static const String _title = 'Flutter Code Sample';
#override
Widget build(BuildContext context) {
return MaterialApp(
title: _title,
home: MyStatefulWidget(),
);
}
}
class MyStatefulWidget extends StatefulWidget {
MyStatefulWidget({Key key}) : super(key: key);
#override
_MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
int _selectedPageIndex = 0;
int _previousIndex = 0;
void refresh() {
setState(() {
_selectedPageIndex = _previousIndex;
});
}
void _onItemTapped(int index) {
setState(() {
_previousIndex = _selectedPageIndex;
_selectedPageIndex = index;
});
}
Widget pageCaller(int index) {
print(index);
switch (index) {
case 0:
{
return Category();
}
case 1:
{
return Feed();
}
case 2:
{
print("settings");
return Settings(
callback: refresh,
);
}
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Home'),
),
body: Center(
child: pageCaller(_selectedPageIndex),
),
bottomNavigationBar: _selectedPageIndex == 2
? null
: BottomNavigationBar(
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.home),
title: Text('Category'),
),
BottomNavigationBarItem(
icon: Icon(Icons.business),
title: Text('Feed'),
),
BottomNavigationBarItem(
icon: Icon(Icons.school),
title: Text('Settings'),
),
],
currentIndex: _selectedPageIndex,
selectedItemColor: Colors.amber[800],
onTap: _onItemTapped,
),
);
}
}
class Category extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Text("Category"),
),
);
}
}
class Feed extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Text("Feed"),
),
);
}
}
class Settings extends StatefulWidget {
VoidCallback callback;
Settings({this.callback});
#override
_SettingsState createState() => _SettingsState();
}
class _SettingsState extends State<Settings> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
Text("This is setting page"),
RaisedButton(
onPressed: () {
widget.callback();
},
child: Text("Go back"),
),
],
));
}
}