Exception on OnPressed function while using animateTo function In TabbarView - flutter

Question

I am Trying to write a code for my project which uses a TabBarView with 4 tabs and has a Global Key so that I can Use the Tab controller anywhere in the app,
however when I tried to Call the animateTo Function using an onpressed Function of Raised Button It Keeps Throwing Errors as follows:
Have Already Done This://Tried Creating a function in the same file as the controller to change the view
class MyTabsState extends State<MyTabs> with SingleTickerProviderStateMixin {
static final homePageKey=GlobalKey<MyTabsState>();
TabController tabcontroller;
#override
void initState() {
super.initState();
tabcontroller = new TabController(vsync: this, length: 4);
}
#override
void dispose() {
super.dispose();
tabcontroller.dispose();
}
#override
Widget build(BuildContext context) {
return new Scaffold(
key: homePageKey,
bottomNavigationBar: new Material(
color: mainUiColor,
child: new TabBar(
controller: tabcontroller,
unselectedLabelColor: Colors.grey,
labelColor: Colors.redAccent,
tabs: <Tab>[
new Tab(icon: new Icon(Icons.home)),
new Tab(icon: new Icon(Icons.photo_album)),
new Tab(icon: new Icon(Icons.arrow_back)),
new Tab(icon: new Icon(Icons.favorite)),
])),
body: new TabBarView(controller: tabcontroller, children: <Widget>[
new First(),
new PhotoGallery(),
new Third(),
new SocialMedia(),
]),
);
}
void changePage(){
tabcontroller.animateTo(2);
}
}
I/flutter ( 4993): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════ I/flutter ( 4993): The following NoSuchMethodError was thrown while handling a gesture: I/flutter ( 4993): The method 'changePage' was called on null. I/flutter ( 4993): Receiver: null I/flutter ( 4993): Tried calling: changePage() I/flutter ( 4993): I/flutter ( 4993): When the exception was thrown, this was the stack: I/flutter ( 4993): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5) I/flutter ( 4993): #1 _PhotoGalleryState.build.<anonymous closure> (package:myproject/screenTabs/SecondTab.dart:97:52) I/flutter ( 4993):
#2 _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:511:14) I/flutter ( 4993):
#3 _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:566:30) I/flutter ( 4993):
#4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:166:24) I/flutter ( 4993): #5 TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:240:9) I/flutter ( 4993): #6 TapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:211:7) I/flutter ( 4993): #7 GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:156:27) I/flutter ( 4993): #8
_WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:225:20) I/flutter ( 4993):
#9 _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:199:22) I/flutter ( 4993):
#10 _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7) I/flutter ( 4993):
#11 _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7) I/flutter ( 4993):
#12 _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7) I/flutter ( 4993):
#16 _invoke1 (dart:ui/hooks.dart:233:10) I/flutter ( 4993): #17 _dispatchPointerDataPacket (dart:ui/hooks.dart:154:5) I/flutter ( 4993): (elided 3 frames from package dart:async) I/flutter ( 4993): I/flutter ( 4993): Handler: onTap I/flutter ( 4993): Recognizer: I/flutter ( 4993): TapGestureRecognizer#bfc40(debugOwner: GestureDetector, state: ready, won arena, finalPosition: I/flutter ( 4993): Offset(126.9, 667.6), sent tap down)

Answer 1

If I were a betting man I'd bet you may be trying to call changePage() on one of the pages listed in your tabBarView. A global key doesn't really make the item available anywhere in the app, you'd have to store it somewhere higher up in the widget tree using an inherited widget or pass it down to its children as a property in order to actually use it. It looks like something you may want to consider looking into is a CupertinoTabScaffold. Then you could wrap that around the main views, and work with it there and have it show up across the entire app. This might be a bit easier than using the current setup.