如何在Flutter Android应用程序中的ListView中自动实现AlertDialog框而无需按下任何按钮

Question

我正在做一个项目，我创建了一个RestApi，其中我有汽车的数据，并且每3秒更新一次。汽车位于4条道路的交界处，现在，当汽车向id表示的特定道路靠近时，"is_green"将变为true，而在ListView->中，CircleAvtar将变为绿色，这将表明汽车是否在混合现在我的问题是当bool isGreen = userData[index]["is_green"]将包含值true时，我如何实现AlertDialog框，该框将自动弹出，而无需按下任何按钮。我是新来的，所以我不知道该怎么做。。。请帮我解决

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:async';
import 'dart:convert';
void main() {
runApp(MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData.dark(),
home: Home(),
));
}
class Home extends StatefulWidget {
Home({Key key}) : super(key: key);
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
Map data;
List userData;
Future getData() async {
print("updating data...");
http.Response response = await http.get("http://10.100.101.154:3000/xd");
data = jsonDecode(response.body);
setState(() {
userData = data["data"];
});
}
@override
void initState() {
super.initState();
Timer.periodic(new Duration(seconds: 3), (timer) {
getData();
});
}
Color getColor(bool isGreen) {
if (isGreen == true) {
return Colors.green;
} else {
return Colors.red;
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('SGH'),
centerTitle: true,
),
body: ListView.builder(
itemCount: userData == null ? 0 : userData.length,
itemBuilder: (BuildContext context, int index) {
bool isGreen = userData[index]["is_green"];
return Card(
child: Row(
children: <Widget>[
Padding(
padding: EdgeInsets.all(10),
child: CircleAvatar(
backgroundColor: getColor(isGreen),
minRadius: 6,
),
),
Padding(
padding: EdgeInsets.all(10),
child: Wrap(
direction: Axis.horizontal,
children: <Widget>[
Text(
"Road Id = ${userData[index]["id"]} CarInQueue = ${userData[index]["car_que"]} nIsGreen ? --> ${userData[index]["is_green"]} ",
style: TextStyle(
fontSize: 20, fontWeight: FontWeight.bold),
),
],
),
),
],
),
);
}),
);
}
}

Answer 1

只要在任何时候更新汽车列表就可以了。。。然后显示一个Dialog，其中包含关于哪辆车正在通过的信息

Future getData() async {
print("updating data...");
http.Response response = await http.get("http://10.100.101.154:3000/xd");
data = jsonDecode(response.body);
setState(() {
userData = data["data"];
});
checkDialog();
}

checkDialog(){
var item = userData.where((car)=>car["is_green"]).first;//this is the first car where is_green is true
if(item!=null){
showDialog(context:context,
builder:(BuildContext context)=>AlertDialog( 
//.... content here
));
}
}