我的目标：当用户按下“ _mainListItem”中的“列表”按钮时，我希望列表视图按orderBy排序。以及在屏幕上更新
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
class mainlist extends StatefulWidget {
@override
_mainlistpage createState() => _mainlistpage();
}
class _mainlistpage extends State<mainlist> {
Widget homePage() {
return StreamBuilder(
stream: Firestore.instance.collection("Test").snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return Text("Loading");
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) =>
_mainListItem(context, snapshot.data.documents[index]));
},
);
}
Widget _mainListItem(BuildContext context, DocumentSnapshot document) {
return Card(
color: Colors.white,
child: InkWell(
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => profile(context, document)));
},
child: Container(
width: double.infinity,
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Container(
decoration: BoxDecoration(
border: Border(bottom: BorderSide(color: Colors.black12))),
child: Row(
children: [
Expanded(
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Column(
children: <Widget>[
Stack(
alignment: Alignment.topRight,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(right: 5),
child: ClipRRect(
borderRadius:
BorderRadius.circular(0.0),
child: FittedBox(
child: Image.asset(
"assets/Profile Picture.png",
fit: BoxFit.fill,
)),
),
),
Padding(
padding: const EdgeInsets.only(
top: 7, right: 4),
child: Text(
'Test',
style: TextStyle(fontSize: 12),
),
),
]),
Row()
],
),
Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
document['name'],
),
// Text("2km"),
],
),
],
),
],
),
),
],
),
),
Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 5, bottom: 5),
child: Row(
children: <Widget>[
Padding(
padding: const EdgeInsets.only(left: 10, right: 7),
child: Container(
child: Material(
borderRadius: BorderRadius.circular(5),
shadowColor: Colors.black,
elevation: 1,
child: SizedBox(
height: 28,
width: 68,
child: IconButton(
padding: EdgeInsets.only(bottom: 10),
**icon: Icon(Icons.list),
disabledColor: Colors.blue,
iconSize: 25,**
)),
),
),
),
],
),
)
],
)
],
),
),
),
);
}
@override
Widget build(BuildContext context) {
// TODO: implement build
return new Scaffold(
backgroundColor: Colors.grey,
appBar: AppBar(
backgroundColor: Colors.grey,
leading: IconButton(
icon: Icon(Icons.arrow_back_ios),
color: Colors.red,
),
title: Text("Test"),
centerTitle: true,
actions: <Widget>[
IconButton(
icon: Icon(Icons.menu),
iconSize: 30,
color: Colors.white,
)
],
),
body: homePage(),
);
}
}
我尝试过 -将streambuilder函数添加到列表按钮中的ontapped： -阅读并观看了每个视频，仍然找不到解决方法
注意：该应用看上去很奇怪，因为我删除了不必要的信息
答案 0 :(得分：1)
您可以在快照方法之前对列表项进行排序，例如：
.orderBy('sortField', descending: true).snapshot()
我希望这对您有用。
答案 1 :(得分：0)
尝试将值映射到const qrcode = window.qrcode;
const video = document.createElement("video");
const canvasElement = document.getElementById("qr-canvas");
const canvas = canvasElement.getContext("2d");
const qrResult = document.getElementById("qr-result");
const outputData = document.getElementById("outputData");
const btnScanQR = document.getElementById("btn-scan-qr");
let scanning = false;
qrcode.callback = res => {
if (res) {
outputData.innerText = res;
scanning = false;
video.srcObject.getTracks().forEach(track => {
track.stop();
});
qrResult.hidden = false;
canvasElement.hidden = true;
btnScanQR.hidden = false;
}
};
btnScanQR.onclick = () => {
navigator.mediaDevices
.getUserMedia({ video: { facingMode: "environment" } })
.then(function(stream) {
scanning = true;
qrResult.hidden = true;
btnScanQR.hidden = true;
canvasElement.hidden = false;
video.setAttribute("playsinline", true); // required to tell iOS safari we don't want fullscreen
video.srcObject = stream;
video.play();
tick();
scan();
});
};
function tick() {
canvasElement.height = video.videoHeight;
canvasElement.width = video.videoWidth;
canvas.drawImage(video, 0, 0, canvasElement.width, canvasElement.height);
scanning && requestAnimationFrame(tick);
}
function scan() {
try {
qrcode.decode();
} catch (e) {
setTimeout(scan, 300);
}
}
并在列表视图中使用对象列表。
答案 2 :(得分：0)
我建议您使用状态来确定列表的排序方式。 这就是我要做的（从相同的代码继续）：
...
class _mainlistpage extends State<mainlist> {
String _orderBy = 'defaultSort'; //? HERE YOU PUT WHAT YOUR SORTING FIELD NAME IS
bool _isDescending = true; //? THIS IS WHAT WILL SET THE ORDER SORTING
Widget homePage() {
return StreamBuilder(
stream: Firestore.instance
.collection("Test")
.orderBy(_orderBy, descending: _isDescending) //? PUT THE ORDERBY QUERY HERE
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) return Text("Loading");
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) =>
_mainListItem(context, snapshot.data.documents[index]));
},
);
}
...
在类中的某个位置，放置按钮或下拉菜单，然后使用setState（...）设置 新变量的状态。
注意：您可能必须在Firestore中创建“索引”。新的时候会出现错误 索引是必需的。