How to Conditionally Route Using One Button? (Flutter) - dart

Question

I have a scene (collections.dart) that takes an index of several other scenes/files in a PageView.builder. You can swipe between scenes from the collections.dart file. Also in collections.dart is a button.
I want it to be the case that if you click on the button, and the current scene being shown through collections.dart is, for example, FirstScreen, then I can route to a table I have built specifically for first.dart, with the same being true for all other scenes in the index.
I have tried to accomplish this by a conditional statement in the onPressed argument, but no success yet. There is no error, it just takes no action. Here is the code in its entirety for collections.dart (including the unsuccessful conditional statement for onPressed):
import 'package:flutter/material.dart';
import 'package:circle_indicator/circle_indicator.dart';
import 'first.dart';
import 'second.dart';
import 'third.dart';
import 'fourth.dart';
import 'fifth.dart';
import 'sixth.dart';
import 'seventh.dart';
import 'eighth.dart';
import 'ninth.dart';
import 'tenth.dart';
class CollectionsScreen extends StatelessWidget {
#override
Widget build(BuildContext context){
return Collections();
}
}
class Collections extends StatefulWidget {
#override
CollectionsState createState() => CollectionsState();
}
class CollectionsState extends State<Collections> {
FirstScreen one;
SecondScreen two;
ThirdScreen three;
FourthScreen four;
FifthScreen five;
SixthScreen six;
SeventhScreen seven;
EighthScreen eight;
NinthScreen nine;
TenthScreen ten;
List<Widget> pages;
#override
void initState() {
one = FirstScreen();
two = SecondScreen();
three = ThirdScreen();
four = FourthScreen();
five = FifthScreen();
six = SixthScreen();
seven = SeventhScreen();
eight = EighthScreen();
nine = NinthScreen();
ten = TenthScreen();
pages = [one, two, three, four, five, six, seven, eight, nine, ten];
super.initState();
}
final PageController controller = new PageController();
#override
Widget build(BuildContext context){
return new Stack(
children: <Widget>[
new Scaffold(
body: new Container(
child: new PageView.builder( //Swipe Between Pages
controller: controller,
itemCount: 10,
itemBuilder: (context, index){
return pages[index];
}
),
),
),
new Container( //CircleIndicator
child: new CircleIndicator(controller, 10, 8.0, Colors.white70, Colors.white,),
alignment: Alignment(0.0, 0.9),
),
new Container( //Button
alignment: Alignment(0.0, 0.65),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
new Container(
child: new RaisedButton(
elevation: 4.0,
child: new Text(
'SHOW ME',
style: new TextStyle(
fontWeight: FontWeight.w900,
fontSize: 22.0,
),
),
color: Color(0xFF70E0EF),
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(7.5)
),
//This is the conditional statement I'm talking about
onPressed: () {
new PageView.builder(
controller: controller,
itemBuilder: (context, index) {
if (pages[index] == one){
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new FirstTable()),
);
}
else if (pages[index] == two){
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new SecondTable()),
);
}
else {
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new ThirdTable()),
);
}
}
);
},
),
width: 150.0,
height: 60.0,
),
],
),
),
],
);
}
}
The "Table" classes I'm referring to in the conditional statement are in the files for first.dart, second.dart, etc. Here is the file for first.dart. For the moment, the code is identical between all these files (first.dart, second.dart, etc.):
import 'package:flutter/material.dart';
class FirstScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new First();
}
}
class First extends StatefulWidget {
#override
FirstState createState() => FirstState();
}
class FirstState extends State<First>{
#override
Widget build(BuildContext context) {
double fontSize = MediaQuery.of(context).size.height;
double fontSizeFractional = fontSize * 0.07;
return Scaffold(
body: new Stack(
fit: StackFit.passthrough,
children: [
new Container( //Background
decoration: new BoxDecoration(
image: new DecorationImage(
image: new AssetImage('assets/FirstBG.png'),
fit: BoxFit.cover
),
),
),
new Container( //Title
margin: EdgeInsets.all(40.0),
alignment: new Alignment(0.0, -0.70),
child: new Text(
'FIRST',
style: new TextStyle(
fontWeight: FontWeight.bold,
fontSize: fontSizeFractional,
color: Colors.white,
fontFamily: 'baron neue',
),
),
),
],
),
);
}
}
class FirstTable extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Table();
}
}
class Table extends StatefulWidget {
#override
TableState createState() => TableState();
}
class TableState extends State<Table>{
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: new RaisedButton(
onPressed: () {
Navigator.pop(context);
},
child: new Text(
'Go Back',
),
),
),
);
}
}
I have a theory that the reason it isn't working is that collections.dart isn't actually caching any data as to what page of the index it is on (that could be totally wrong, though). Curious to hear your ideas!

Answer 1

Your problem is that you should directly use controller.page inside the onPressed of your button. instead of instantiating a widget.
Although ultimately you should hide an abstract layer between your gallery class and the list of items.
To do that you can create a custom class which will hols all informations about a gallery item :
#immutable
class GalleryItem {
final Widget content;
final Widget details;
GalleryItem({#required this.content, this.details}) : assert(content != null);
}
Your gallery will then take a list of such class as parameter. And do it's job with these.
Ideally you want to use your gallery like this :
Gallery(
items: [
GalleryItem(
content: Container(
color: Colors.red,
),
details: Text("red"),
),
GalleryItem(
content: Container(
color: Colors.blue,
),
details: Text("blue"),
),
],
),
The code of such gallery would be :
class Gallery extends StatefulWidget {
final List<GalleryItem> items;
Gallery({#required this.items, Key key})
: assert(items != null),
super(key: key);
#override
_GalleryState createState() => _GalleryState();
}
class _GalleryState extends State<Gallery> {
final PageController pageController = PageController();
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
Expanded(
child: PageView(
children: widget.items.map((item) => item.content).toList(),
controller: pageController,
),
),
RaisedButton(
onPressed: showContentDetails,
child: Text("More info"),
)
],
);
}
void showContentDetails() {
final index = pageController.page.round();
if (widget.items[index]?.details != null) {
showDialog(
context: context,
builder: (_) =>
GalleryItemDetails(details: widget.items[index].details),
);
}
}
}
class GalleryItemDetails extends StatelessWidget {
final Widget details;
GalleryItemDetails({#required this.details, Key key})
: assert(details != null),
super(key: key);
#override
Widget build(BuildContext context) {
return Dialog(
child: details,
);
}
}