正如標題所述，我正在嘗試使用 json MAP 從嵌套物件中提取資料。我希望我正確地描述了這一點。我是飛鏢新手，但我仍在成長為一名程式員。這是我的模型的代碼。
class Device {
List<DevicesModel> _devices = [];
Page? _page;
List<DevicesModel> get devices => _devices;
Device({required devices, required page}) {
this._devices = devices;
this._page = page;
}
Device.fromJson(Map<String, dynamic> json) {
if (json['devices'] != null) {
_devices = <DevicesModel>[];
json['devices'].forEach((v) {
_devices.add(DevicesModel.fromJson(v));
});
}
}
}
class DevicesModel {
late final String deviceId;
String? publicId;
String? companyId;
late final String company;
late final String label;
String? imei;
String? sim;
String? mobileProviderId;
String? mobileProvider;
String? hologramDeviceId;
String? hologramLinkId;
String? firmwareVersionId;
String? version;
String? formattedVersion;
String? deviceTypeId;
String? deviceType;
String? ipAddress;
String? recordInterval;
String? uploadInterval;
String? powerMode;
String? connectivity;
String? connectivityClass;
String? usersLastRecordDate;
String? gmtLastRecordDate;
String? battery;
String? batteryPercentage;
String? batteryClass;
String? batteryIcon;
String? signalQuality;
late final String signalQualityClass;
String? signalQualityText;
String? signalQualityIcon;
String? queuedRecords;
String? command;
String? status;
String? statusClass;
String? purchaseDate;
String? warrantyPeriod;
String? warrantyExpires;
String? warrantyStatus;
String? temperatureClass;
late final String temperatureMetric;
late final String temperatureImperial;
String? surgeProtection;
String? totalProducts;
Null temperatureLowThreshold;
Null temperatureHighThreshold;
Null notes;
Null importId;
String? deleted;
String? createdBy;
String? lastUpdatedBy;
Null deletedBy;
Null dateCreated;
String? dateModified;
Null dateDeleted;
String? scope;
String? owner;
late List<Ports> ports;
DevicesModel(
{required this.deviceId,
this.publicId,
this.companyId,
required this.company,
required this.label,
this.imei,
this.sim,
this.mobileProviderId,
this.mobileProvider,
this.hologramDeviceId,
this.hologramLinkId,
this.firmwareVersionId,
this.version,
this.formattedVersion,
this.deviceTypeId,
this.deviceType,
this.ipAddress,
this.recordInterval,
this.uploadInterval,
this.powerMode,
this.connectivity,
this.connectivityClass,
this.usersLastRecordDate,
this.gmtLastRecordDate,
this.battery,
this.batteryPercentage,
this.batteryClass,
this.batteryIcon,
this.signalQuality,
required this.signalQualityClass,
this.signalQualityText,
this.signalQualityIcon,
this.queuedRecords,
this.command,
this.status,
this.statusClass,
this.purchaseDate,
this.warrantyPeriod,
this.warrantyExpires,
this.warrantyStatus,
this.temperatureClass,
required this.temperatureMetric,
required this.temperatureImperial,
this.surgeProtection,
this.totalProducts,
this.temperatureLowThreshold,
this.temperatureHighThreshold,
this.notes,
this.importId,
this.deleted,
this.createdBy,
this.lastUpdatedBy,
this.deletedBy,
this.dateCreated,
this.dateModified,
this.dateDeleted,
this.scope,
this.owner,
required this.ports
});
DevicesModel.fromJson(Map<String, dynamic> json) {
deviceId = json['device_id'];
publicId = json['public_id'];
companyId = json['company_id'];
company = json['company'] ?? 'unknown';
label = json['label'] ?? 'unknown';
imei = json['imei'];
sim = json['sim'];
mobileProviderId = json['mobile_provider_id'];
mobileProvider = json['mobile_provider'];
hologramDeviceId = json['hologram_device_id'];
hologramLinkId = json['hologram_link_id'];
firmwareVersionId = json['firmware_version_id'];
version = json['version'];
formattedVersion = json['formatted_version'];
deviceTypeId = json['device_type_id'];
deviceType = json['device_type'];
ipAddress = json['ip_address'];
recordInterval = json['record_interval'];
uploadInterval = json['upload_interval'];
powerMode = json['power_mode'];
connectivity = json['connectivity'];
connectivityClass = json['connectivity_class'];
usersLastRecordDate = json['users_last_record_date'];
gmtLastRecordDate = json['gmt_last_record_date'];
battery = json['battery'];
batteryPercentage = json['battery_percentage'];
batteryClass = json['battery_class'];
batteryIcon = json['battery_icon'];
signalQuality = json['signal_quality'];
signalQualityClass = json['signal_quality_class'];
signalQualityText = json['signal_quality_text'];
signalQualityIcon = json['signal_quality_icon'];
queuedRecords = json['queued_records'];
command = json['command'];
status = json['status'];
statusClass = json['status_class'];
purchaseDate = json['purchase_date'];
warrantyPeriod = json['warranty_period'];
warrantyExpires = json['warranty_expires'];
warrantyStatus = json['warranty_status'];
temperatureClass = json['temperature_class'];
temperatureMetric = json['temperature_metric'] ?? 'n/a';
temperatureImperial = json['temperature_imperial'] ?? 'n/a';
surgeProtection = json['surge_protection'];
totalProducts = json['total_products'];
temperatureLowThreshold = json['temperature_low_threshold'];
temperatureHighThreshold = json['temperature_high_threshold'];
notes = json['notes'];
importId = json['import_id'];
deleted = json['deleted'];
createdBy = json['created_by'];
lastUpdatedBy = json['last_updated_by'];
deletedBy = json['deleted_by'];
dateCreated = json['date_created'];
dateModified = json['date_modified'];
dateDeleted = json['date_deleted'];
scope = json['scope'];
owner = json['owner'];
if (json['ports'] != null) {
ports = <Ports>[];
json['ports'].forEach((v) {
ports.add(new Ports.fromJson(v));
});
}
}
}
class Ports {
List<PortsModel> _ports = [];
List<PortsModel> get ports => _ports;
Ports({required ports}) {
this._ports = ports;
}
Ports.fromJson(Map<String, dynamic> json) {
if (json['ports'] != null) {
_ports = <PortsModel>[];
json['ports'].forEach((v) {
_ports.add(PortsModel.fromJson(v));
});
}
}
}
class PortsModel {
String? devicePortsId;
String? deviceId;
String? companyId;
String? company;
String? productId;
late final String productName;
String? portNumber;
String? version;
String? sensorTypeId;
String? sensorType;
String? sensorDescription;
String? imperialSymbol;
String? metricSymbol;
String? fillVolumeGallons;
String? fillVolumeLiters;
String? totalGallonsCapacity;
String? totalLitersCapacity;
String? percentFull;
String? tankTypeId;
String? tankType;
String? slug;
String? imageUrl;
String? formula;
String? reorderYellow;
String? reorderRed;
String? deleted;
Null? createdBy;
String? lastUpdatedBy;
Null? deletedBy;
String? dateCreated;
String? dateModified;
Null? dateDeleted;
String? scope;
String? owner;
PortsModel(
{this.devicePortsId,
this.deviceId,
this.companyId,
this.company,
this.productId,
required this.productName,
this.portNumber,
this.version,
this.sensorTypeId,
this.sensorType,
this.sensorDescription,
this.imperialSymbol,
this.metricSymbol,
this.fillVolumeGallons,
this.fillVolumeLiters,
this.totalGallonsCapacity,
this.totalLitersCapacity,
this.percentFull,
this.tankTypeId,
this.tankType,
this.slug,
this.imageUrl,
this.formula,
this.reorderYellow,
this.reorderRed,
this.deleted,
this.createdBy,
this.lastUpdatedBy,
this.deletedBy,
this.dateCreated,
this.dateModified,
this.dateDeleted,
this.scope,
this.owner});
PortsModel.fromJson(Map<String, dynamic> json) {
devicePortsId = json['device_ports_id'];
deviceId = json['device_id'];
companyId = json['company_id'];
company = json['company'];
productId = json['product_id'];
productName = json['product_name'] ?? 'unknown';
portNumber = json['port_number'];
version = json['version'];
sensorTypeId = json['sensor_type_id'];
sensorType = json['sensor_type'];
sensorDescription = json['sensor_description'];
imperialSymbol = json['imperial_symbol'];
metricSymbol = json['metric_symbol'];
fillVolumeGallons = json['fill_volume_gallons'];
fillVolumeLiters = json['fill_volume_liters'];
totalGallonsCapacity = json['total_gallons_capacity'];
totalLitersCapacity = json['total_liters_capacity'];
percentFull = json['percent_full'];
tankTypeId = json['tank_type_id'];
tankType = json['tank_type'];
slug = json['slug'];
imageUrl = json['image_url'];
formula = json['formula'];
reorderYellow = json['reorder_yellow'];
reorderRed = json['reorder_red'];
deleted = json['deleted'];
createdBy = json['created_by'];
lastUpdatedBy = json['last_updated_by'];
deletedBy = json['deleted_by'];
dateCreated = json['date_created'];
dateModified = json['date_modified'];
dateDeleted = json['date_deleted'];
scope = json['scope'];
owner = json['owner'];
}
}
class Page {
int? totalRecords;
int? pageNum;
int? pageSize;
Null? previousPage;
String? nextPage;
Null? searchString;
Page(
{this.totalRecords,
this.pageNum,
this.pageSize,
this.previousPage,
this.nextPage,
this.searchString});
Page.fromJson(Map<String, dynamic> json) {
totalRecords = json['total_records'];
pageNum = json['page_num'];
pageSize = json['page_size'];
previousPage = json['previous_page'];
nextPage = json['next_page'];
searchString = json['search_string'];
}
}
其次是我試圖列印出嵌套資料的地方。
import 'package:auto_size_text/auto_size_text.dart';
import 'package:flutter/material.dart';
import 'package:gateway_device/controllers/device_controller.dart';
import 'package:gateway_device/flutter_flow/flutter_flow_theme.dart';
import 'package:gateway_device/models/devices_model.dart';
import 'package:gateway_device/routes/route_helper.dart';
import 'package:gateway_device/tank_product/tank_product_widget.dart';
import 'package:get/get.dart';
import 'package:percent_indicator/linear_percent_indicator.dart';
class TankProductComponent extends StatefulWidget {
TankProductComponent({Key? key}) : super(key: key);
@override
State<TankProductComponent> createState() => _TankProductComponent();
}
class _TankProductComponent extends State<TankProductComponent> {
@override
Widget build(BuildContext context) {
return GetBuilder<DeviceController>(builder: (devices) {
// print(devices);
return Container(
height: 514,
child: ListView.builder(
physics: AlwaysScrollableScrollPhysics(),
shrinkWrap: true,
scrollDirection: Axis.vertical,
itemCount: 3,
itemBuilder: (context, position) {
return _buildPageItem(position, devices.deviceList[position]);
}),
);
});
}
Widget _buildPageItem(int index, DevicesModel device) {
getPorts() {
var ports = device.ports;
if (device.ports != [null]) {
return ports;
}
}
print(getPorts());
}
}
我遇到的問題是錯誤告訴我'LateError（LateInitializationError：欄位'埠'尚未初始化。）'
我正在努力弄清楚如何成功地做到這一點。請幫忙！提前向您表示誠摯的感謝。
uj5u.com熱心網友回復：
該錯誤很可能是由以下原因引起的：
if (json['ports'] != null) {
ports = <Ports>[];
json['ports'].forEach((v) {
ports.add(new Ports.fromJson(v));
});
}
}
如果 json 回應包含埠，您將有條件地初始化模型的埠欄位。將代碼更改為此可能會解決您的問題：
ports = <Ports>[];
if (json['ports'] != null) {
json['ports'].forEach((v) {
ports.add(new Ports.fromJson(v));
});
}
}
注意，你的欄位是遲到的，但是在使用之前必須先初始化，所以條件初始化勢必會帶來麻煩。另外我建議將相關欄位分組到模型中，擁有 100 個欄位的模型并不是一個好習慣。
轉載請註明出處，本文鏈接：https://www.uj5u.com/caozuo/478585.html
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