AzSumToshko
Reputation: 9
Flutter: getting Null check operator used on a null value error after navigating from widget to widget with BottomNavigationBar
I am currently building Flutter mobile shop application. I just did the home page where i store 4 pages in a list and call them depending on which bottom navigation bar item i chose. When i start the application all the widgets and stuff work fine, but when i go to another page from the bottom navigation bar and go back to the MainPage i get the null check operator used on a null value error and i dont know why. Just to note i am using GetX for state managment and firebase for database.
Here is the expanded error :
======== Exception caught by widgets library
=======================================================
The following _CastError was thrown building PageBody(state: _PageBodyState#e8ed4):
Null check operator used on a null value
The relevant error-causing widget was:
PageBody
PageBody:file:///C:/Users/s_dob/StudioProjects/
auto_point_mobile/lib/pages/home/main_page.dart:62:20
When the exception was thrown, this was the stack:
#0 GetBuilderState.initState
(package:get/get_state_manager/src/simple/get_state.dart:134:40)
#1 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:5101:55)
#2 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4944:5)
#3 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3953:16)
#4 Element.updateChild (package:flutter/src/widgets/framework.dart:3676:20)
#5 ComponentElement.performRebuild
(package:flutter/src/widgets/framework.dart:4993:16)
#6 StatefulElement.performRebuild
(package:flutter/src/widgets/framework.dart:5133:11)
#7 Element.rebuild (package:flutter/src/widgets/framework.dart:4690:5)
#8 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2743:19)
#9 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:863:21)
#10 RendererBinding._handlePersistentFrameCallback
(package:flutter/src/rendering/binding.dart:381:5)
#11 SchedulerBinding._invokeFrameCallback
(package:flutter/src/scheduler/binding.dart:1289:15)
#12 SchedulerBinding.handleDrawFrame
(package:flutter/src/scheduler/binding.dart:1218:9)
#13 SchedulerBinding._handleDrawFrame
(package:flutter/src/scheduler/binding.dart:1076:5)
#14 _invoke (dart:ui/hooks.dart:145:13)
#15 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:338:5)
#16 _drawFrame (dart:ui/hooks.dart:112:31)
========================================
============================================================
Line 62 in the MainPage widget is child: PageBody()
Here is the MainPage widget :
class MainPage extends StatefulWidget {
const MainPage({Key? key}) : super(key: key);
@override
State<MainPage> createState() => _State();
}
class _State extends State<MainPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
//header
Container(
child: Container(
margin: EdgeInsets.only(top: Dimensions.height30,bottom: Dimensions.height15),
padding: EdgeInsets.only(left: Dimensions.width20,right: Dimensions.width20),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Column(
children: [
BigText(text: "AutoPoint", color: AppColors.mainColor,size: 30),
Row(
children: [
SmallText(text: "AutoPoint", color: Colors.black),
const Icon(Icons.arrow_drop_down_rounded),
],
)
],
),
Center(
child: Container(
width: Dimensions.width45,
height: Dimensions.height45,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(Dimensions.radius15),
color: Colors.orange,
),
child: Icon(Icons.search, color:Colors.white,size: Dimensions.icon24),
),
)
],
),
),
),
//body
Expanded(child: SingleChildScrollView(
child: PageBody(),
)),
],
),
);
}
}
and this is the PageBody :
class PageBody extends StatefulWidget {
const PageBody({Key? key}) : super(key: key);
@override
State<PageBody> createState() => _PageBodyState();
}
class _PageBodyState extends State<PageBody> {
PageController pageController = PageController(viewportFraction: 0.85);
var _currentPageValue = 0.0;
double _scaleFactor = 0.8;
double _height = Dimensions.pageViewContainer;
late final directory;
Future<void> _initAppDir() async {
directory = await getApplicationDocumentsDirectory();
setState(() {});
}
@override
void initState(){
super.initState();
_initAppDir();
pageController.addListener(() {
setState(() {
_currentPageValue = pageController.page ?? _currentPageValue;
});
});
}
@override
void dispose(){
pageController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return GetBuilder<ProductController>(builder: (products){
return products.isLoaded ? Column(
children: [
//slider
Container(
height: Dimensions.pageView,
child: PageView.builder(
controller: pageController,
itemCount: products.productList.length >= 7 ? 7 : products.productList.length,
itemBuilder: (context, position){
return _buildPageItem(position, products.productList[position]);
}),
),
//dots
DotsIndicator(
dotsCount: products.productList.length <= 0 ? 1 : products.productList.length >= 7 ? 7 : products.productList.length,
position: _currentPageValue,
decorator: DotsDecorator(
activeColor: AppColors.mainColor,
size: const Size.square(9.0),
activeSize: const Size(18.0, 9.0),
activeShape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(5.0)),
),
),
//populat text
SizedBox(height: Dimensions.height30,),
Container(
margin: EdgeInsets.only(left: Dimensions.width30),
child: Row(
crossAxisAlignment: CrossAxisAlignment.end,
children: [
BigText(text: "All"),
SizedBox(width: Dimensions.width20,),
Container(
margin: const EdgeInsets.only(bottom: 3),
child: BigText(text: ".",color: Colors.black26,),
),
SizedBox(width: Dimensions.width20,),
Container(
child: SmallText(text: "products",),
),
],
),
),
//list of food and images
ListView.builder(
physics: NeverScrollableScrollPhysics(),
shrinkWrap: true,
itemCount: products.productList.length,
itemBuilder: (context, index){
return GestureDetector(
onTap: (){
Get.toNamed(RouteHelper.getRecommended(index, directory.path, "main"));
},
child: Container(
margin: EdgeInsets.only(left: Dimensions.width20, right: Dimensions.width20, bottom: Dimensions.height10),
child: Row(
children: [
//image section
Container(
width: Dimensions.listViewImgSize,
height: Dimensions.listViewImgSize,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(Dimensions.radius20),
color: AppColors.mainColor,
image: DecorationImage(
image: FileImage(File(directory.path+ "/image/" + products.productList[index].product.id + '.png')),
fit: BoxFit.cover,
),
),
),
//text container
Expanded(
child: Container(
height: Dimensions.listViewTextContSize,
decoration: BoxDecoration(
borderRadius: BorderRadius.only(
topRight: Radius.circular(Dimensions.radius20),
bottomRight: Radius.circular(Dimensions.radius20),
),
color: Colors.white,
),
child: Padding(
padding: EdgeInsets.only(left: Dimensions.width10, right: Dimensions.width10),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.center,
children: [
BigText(text: products.productList[index].product.name),
SizedBox(height: Dimensions.height10,),
Center(child: SmallText(text: "цена: ${products.productList[index].product.price}BGN.")),
SizedBox(height: Dimensions.height10,),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
IconAndTextWidget(icon: Icons.card_membership_outlined,
text: products.productList[index].product.typeOfProduct,
iconColor: AppColors.mainColor),
SizedBox(width: Dimensions.width3,),
IconAndTextWidget(icon: Icons.inventory,
text: "In Stock",
iconColor: AppColors.mainColor),
]
),
],
),
),
),
),
],
),
),
);
}),
],
): Column(
children: [
SizedBox(
width: Dimensions.width45 * 6.3,
height: Dimensions.height45 * 6.3,
),
//The loading animation
SizedBox(
width: Dimensions.width45 * 2,
height: Dimensions.height45 * 2,
child: CircularProgressIndicator(
color: AppColors.mainColor,
),
)
],
);
});
}
Widget _buildPageItem(int index, ProductModel product){
Matrix4 matrix = new Matrix4.identity();
if(index == _currentPageValue.floor()){
var currScale = 1 - (_currentPageValue - index) * (1 - _scaleFactor);
var currTrans = _height * (1 - currScale) /2;
matrix = Matrix4.diagonal3Values(1, currScale ,1);
matrix = Matrix4.diagonal3Values(1, currScale ,1)..setTranslationRaw(0, currTrans, 0);
}else if(index == _currentPageValue.floor() + 1){
var currScale = _scaleFactor + (_currentPageValue-index+1) * (1 - _scaleFactor);
var currTrans = _height * (1 - currScale) /2;
matrix = Matrix4.diagonal3Values(1, currScale ,1);
matrix = Matrix4.diagonal3Values(1, currScale ,1)..setTranslationRaw(0, currTrans, 0);
}else if(index == _currentPageValue.floor() - 1){
var currScale = 1 - (_currentPageValue - index) * (1 - _scaleFactor);
var currTrans = _height * (1 - currScale) /2;
matrix = Matrix4.diagonal3Values(1, currScale ,1);
matrix = Matrix4.diagonal3Values(1, currScale ,1)..setTranslationRaw(0, currTrans, 0);
}else{
var currScale = 0.8;
matrix = Matrix4.diagonal3Values(1, currScale ,1)..setTranslationRaw(0, _height * (1 - _scaleFactor)/2, 1);
}
return Transform(
transform: matrix,
child: Stack(
children: [
GestureDetector(
onTap: (){
Get.toNamed(RouteHelper.getDetails(index, directory.path, "main"));
},
child: Container(
height: _height,
margin: EdgeInsets.only(left: Dimensions.width5, right: Dimensions.width5),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(Dimensions.radius20),
color: AppColors.mainColor,
image: DecorationImage(
image: FileImage(File(directory.path+ "/image/" + product.product.id + '.png')),
fit: BoxFit.cover,
),
),
),
),
Align(
alignment: Alignment.bottomCenter,
child: Container(
height: Dimensions.pageViewTextContainer,
margin: EdgeInsets.only(left: Dimensions.width25, right: Dimensions.width25, bottom: Dimensions.height30),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(Dimensions.radius30),
color: Colors.white,
boxShadow: [
BoxShadow(
color: Color(0xFFe8e8e8),
blurRadius: 5.0,
offset: Offset(0, 5),
),
BoxShadow(
color: Colors.white,
offset: Offset(-5, 0),
),
BoxShadow(
color: Colors.white,
offset: Offset(5, 0),
),
]
),
child: Container(
padding: EdgeInsets.only(top: Dimensions.height15,left: Dimensions.width15,right: Dimensions.width15),
child: AppColumn(productModel: product),
),
),
),
],
),
);
}
}
Upvotes: 0
Views: 390
Answers (1)
AzSumToshko
Reputation: 9
So i fixed it. The thing was that in the GetBuilder of the PageBody when i do another initialization i had to put init:Get.find() and now it works perfectly.
Upvotes: 0