我的顫振小部件出現以下錯誤。地址是可以為空的串列，并且僅獲得該小部件中的索引。我可以知道我該如何解決這個問題。
用于空值的空檢查運算子
對于這條線
Address address = systemData.addresses![index];
地址標題.dart
import 'package:auto_size_text/auto_size_text.dart';
import 'package:flutter/material.dart';
import 'package:thitsarparami/helper/constants.dart';
import 'package:thitsarparami/models/models.dart';
class AddressTile extends StatelessWidget {
final SystemData systemData;
final int index;
const AddressTile({required this.systemData, required this.index, Key? key})
: super(key: key);
@override
Widget build(BuildContext context) {
Address address = systemData.addresses![index];
return Container(
padding: const EdgeInsets.symmetric(
horizontal: 10,
),
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(bottom: 12, top: 12),
child: Container(
padding: const EdgeInsets.all(5),
// width: SizeConfig.screenWidth * 0.78,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(16),
color: Theme.of(context).backgroundColor),
child: Row(children: [
Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
const Icon(
Icons.location_pin,
//size: 30,
),
const SizedBox(width: 4),
Flexible(
child: AutoSizeText(
address.line1Address!,
style: const TextStyle(
fontSize: 18,
fontWeight: FontWeight.bold,
),
),
),
],
),
const SizedBox(
height: 10,
),
Container(
padding: const EdgeInsets.only(left: 20),
child: Column(
children: [
AutoSizeText(
'${address.line2Address!} ${address.township!} ${address.state!} ${address.country!} ${address.postalCode}',
//maxLines: 1,
style: const TextStyle(fontSize: 16),
),
],
),
),
const SizedBox(
height: 10,
),
Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
const Icon(
Icons.phone_outlined,
//size: 30,
),
const SizedBox(width: 4),
Row(
children: [
//const SizedBox(height: 30),
TextButton(
style: TextButton.styleFrom(
textStyle: const TextStyle(fontSize: 16),
),
onPressed: () {
launchURL("tel:${address.phone1!}");
},
child: Text(address.phone1!),
),
const SizedBox(height: 10),
TextButton(
style: TextButton.styleFrom(
textStyle: const TextStyle(fontSize: 16),
),
onPressed: () {
launchURL("tel:${address.phone2!}");
},
child: Text(address.phone2!),
),
],
)
],
),
Divider(
color: Theme.of(context).scaffoldBackgroundColor,
thickness: 2.0,
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
TextButton.icon(
onPressed: () {
launchURL(systemData.facebook!);
},
icon: const Icon(Icons.facebook_outlined),
label: const AutoSizeText("Facebook"),
),
TextButton.icon(
onPressed: () {
launchURL(systemData.messenger!);
},
icon: const Icon(Icons.messenger_outline_sharp),
label: const AutoSizeText("Chat"),
),
TextButton.icon(
onPressed: () {
launchURL(systemData.youtube!);
},
icon: const Icon(Icons.videocam),
label: const AutoSizeText("Youtube"),
),
],
)
],
),
),
]),
),
);
}
}
system_data.dart
import 'dart:convert';
import 'package:equatable/equatable.dart';
class YouTube extends Equatable {
final String? videoId;
final String? videoTitle;
const YouTube({this.videoId, this.videoTitle});
static YouTube fromJson(dynamic json) {
return YouTube(
videoId: json['video_id'],
videoTitle: json['video_title'],
);
}
static List<YouTube> youtubeFromJson(String str) =>
List<YouTube>.from(json.decode(str).map((x) => YouTube.fromJson(x)));
@override
List<Object?> get props => [videoId];
}
class Address extends Equatable {
final int id;
final String? line1Address;
final String? line2Address;
final String? township;
final String? state;
final String? country;
final String? postalCode;
final String? phone1;
final String? phone2;
const Address({
required this.id,
this.line1Address,
this.line2Address,
this.township,
this.state,
this.country,
this.postalCode,
this.phone1,
this.phone2,
});
static Address fromJson(dynamic json) {
return Address(
id: json['id'],
line1Address: json['line1_address'],
line2Address: json['line2_address'],
township: json['township'],
state: json['state'],
country: json['country'],
postalCode: json['postal_code'],
phone1: json['phone1'],
phone2: json['phone2'],
);
}
static List<Address> addressesFromJson(String str) =>
List<Address>.from(json.decode(str).map((x) => Address.fromJson(x)));
@override
List<Object?> get props => [id];
}
// ignore: must_be_immutable
class SystemData extends Equatable {
String? biography;
String? headMonkImageUrl;
String? headMonkThumbnail;
String? aboutThitsarparami;
List<Address>? addresses;
String? facebook;
String? messenger;
String? youtube;
String? apk;
String? fbShareMonk;
String? fbShareAlbum;
String? fbShareDhammaTalk;
YouTube? youtubeLive;
SystemData(
{this.biography,
this.headMonkImageUrl,
this.headMonkThumbnail,
this.aboutThitsarparami,
this.addresses,
this.facebook,
this.messenger,
this.youtube,
this.apk,
this.fbShareMonk,
this.fbShareAlbum,
this.fbShareDhammaTalk,
this.youtubeLive});
@override
List<Object> get props => [biography!];
static SystemData systemDataFromJson(List<dynamic> maps) {
final SystemData about = SystemData();
for (var element in maps) {
if (element["code"] == "biography") about.biography = element["metadata"];
if (element["code"] == "head_monk_image_url") {
about.headMonkImageUrl = element["metadata"];
}
if (element["code"] == "head_monk_thumbnail") {
about.headMonkThumbnail = element["metadata"];
}
if (element["code"] == "about_thitsarparami") {
about.aboutThitsarparami = element["metadata"];
}
if (element["code"] == "facebook") about.facebook = element["metadata"];
if (element["code"] == "messenger") about.messenger = element["metadata"];
if (element["code"] == "youtube") about.youtube = element["metadata"];
if (element["code"] == "apk") about.apk = element["metadata"];
if (element["code"] == "fb_share_monk") {
about.fbShareMonk = element["metadata"];
}
if (element["code"] == "fb_share_album") {
about.fbShareAlbum = element["metadata"];
}
if (element["code"] == "fb_share_dhamma_talk") {
about.fbShareDhammaTalk = element["metadata"];
}
if (element["code"] == "addresses") {
about.addresses = Address.addressesFromJson(element["metadata"]);
}
if (element["code"] == "youtube_live") {
about.youtubeLive = YouTube.youtubeFromJson(element["metadata"]).first;
}
}
return about;
}
@override
String toString() => 'About {id: $biography}';
}
uj5u.com熱心網友回復：
嘗試使用這個類：
class AddressTile extends StatelessWidget {
final SystemData systemData;
final int index;
const AddressTile({required this.systemData, required this.index, Key? key})
: super(key: key);
@override
Widget build(BuildContext context) {
if (systemData.addresses == null || systemData.addresses!.length < index) {
return Container();
}
Address address = systemData.addresses![index];
return Container(
padding: const EdgeInsets.symmetric(
horizontal: 10,
),
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(bottom: 12, top: 12),
child: Container(
padding: const EdgeInsets.all(5),
// width: SizeConfig.screenWidth * 0.78,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(16),
color: Theme.of(context).backgroundColor),
child: Row(children: [
Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
const Icon(
Icons.location_pin,
//size: 30,
),
const SizedBox(width: 4),
Flexible(
child: AutoSizeText(
address.line1Address!,
style: const TextStyle(
fontSize: 18,
fontWeight: FontWeight.bold,
),
),
),
],
),
const SizedBox(
height: 10,
),
Container(
padding: const EdgeInsets.only(left: 20),
child: Column(
children: [
AutoSizeText(
'${address.line2Address!} ${address.township!} ${address.state!} ${address.country!} ${address.postalCode}',
//maxLines: 1,
style: const TextStyle(fontSize: 16),
),
],
),
),
const SizedBox(
height: 10,
),
Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
const Icon(
Icons.phone_outlined,
//size: 30,
),
const SizedBox(width: 4),
Row(
children: [
//const SizedBox(height: 30),
TextButton(
style: TextButton.styleFrom(
textStyle: const TextStyle(fontSize: 16),
),
onPressed: () {
launchURL("tel:${address.phone1!}");
},
child: Text(address.phone1!),
),
const SizedBox(height: 10),
TextButton(
style: TextButton.styleFrom(
textStyle: const TextStyle(fontSize: 16),
),
onPressed: () {
launchURL("tel:${address.phone2!}");
},
child: Text(address.phone2!),
),
],
)
],
),
Divider(
color: Theme.of(context).scaffoldBackgroundColor,
thickness: 2.0,
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
TextButton.icon(
onPressed: () {
launchURL(systemData.facebook!);
},
icon: const Icon(Icons.facebook_outlined),
label: const AutoSizeText("Facebook"),
),
TextButton.icon(
onPressed: () {
launchURL(systemData.messenger!);
},
icon: const Icon(Icons.messenger_outline_sharp),
label: const AutoSizeText("Chat"),
),
TextButton.icon(
onPressed: () {
launchURL(systemData.youtube!);
},
icon: const Icon(Icons.videocam),
label: const AutoSizeText("Youtube"),
),
],
)
],
),
),
]),
),
);
}
}
uj5u.com熱心網友回復：
正如您所看到的，您已經添加!了可空值，addresses您不能這樣做，因為addresses可以為空address且不為空。您可以將任一地址設定為可空的，例如
Address? address = systemData.addresses![index];或者
如果不為空則賦值
if (systemData.addresses !=null){
Address address = systemData.addresses![index];
}
轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/491921.html