flutter - 如何在flutter中创建和导出csv文件？

Question

我有 List<> 数据

List<dynamic> associateList = [
{"number": 1, "lat": "14.97534313396318", "lon": "101.22998536005622"},
{"number": 2, "lat": "14.97534313396318", "lon": "101.22998536005622"},
{"number": 3, "lat": "14.97534313396318", "lon": "101.22998536005622"},
{"number": 4, "lat": "14.97534313396318", "lon": "101.22998536005622"}

];
我想要像它这样的 csv 文件。

以及如何将文件导出到设备？

Answer 1

您可以在下面复制粘贴运行完整代码
以下工作演示将文件写入 Downloads 目录并使用 CSV Viwer 查看文件
第一步:在<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />中加入AndroidManifest.xml第 2 步:使用包 permission_handler 请求权限
第 3 步:获取包含 ext_storage 包的下载目录
第 4 步:使用包 csv 的 ListToCsvConverter()代码片段

Map<Permission, PermissionStatus> statuses = await [
  Permission.storage,
].request();

List<dynamic> associateList = [
  {"number": 1, "lat": "14.97534313396318", "lon": "101.22998536005622"},
  {"number": 2, "lat": "14.97534313396318", "lon": "101.22998536005622"},
  {"number": 3, "lat": "14.97534313396318", "lon": "101.22998536005622"},
  {"number": 4, "lat": "14.97534313396318", "lon": "101.22998536005622"}
];

List<List<dynamic>> rows = [];

List<dynamic> row = [];
row.add("number");
row.add("latitude");
row.add("longitude");
rows.add(row);
for (int i = 0; i < associateList.length; i++) {
  List<dynamic> row = [];
  row.add(associateList[i]["number"] - 1);
  row.add(associateList[i]["lat"]);
  row.add(associateList[i]["lon"]);
  rows.add(row);
}

String csv = const ListToCsvConverter().convert(rows);

String dir = await ExtStorage.getExternalStoragePublicDirectory(
    ExtStorage.DIRECTORY_DOWNLOADS);
print("dir $dir");
String file = "$dir";

File f = File(file + "/filename.csv");

f.writeAsString(csv);

工作演示

完整代码

import 'package:csv/csv.dart';
import 'package:flutter/material.dart';
import 'package:ext_storage/ext_storage.dart';
import 'dart:io';
import 'package:permission_handler/permission_handler.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _generateCsvFile() async {
    Map<Permission, PermissionStatus> statuses = await [
      Permission.storage,
    ].request();

    List<dynamic> associateList = [
      {"number": 1, "lat": "14.97534313396318", "lon": "101.22998536005622"},
      {"number": 2, "lat": "14.97534313396318", "lon": "101.22998536005622"},
      {"number": 3, "lat": "14.97534313396318", "lon": "101.22998536005622"},
      {"number": 4, "lat": "14.97534313396318", "lon": "101.22998536005622"}
    ];

    List<List<dynamic>> rows = [];

    List<dynamic> row = [];
    row.add("number");
    row.add("latitude");
    row.add("longitude");
    rows.add(row);
    for (int i = 0; i < associateList.length; i++) {
      List<dynamic> row = [];
      row.add(associateList[i]["number"] - 1);
      row.add(associateList[i]["lat"]);
      row.add(associateList[i]["lon"]);
      rows.add(row);
    }

    String csv = const ListToCsvConverter().convert(rows);

    String dir = await ExtStorage.getExternalStoragePublicDirectory(
        ExtStorage.DIRECTORY_DOWNLOADS);
    print("dir $dir");
    String file = "$dir";

    File f = File(file + "/filename.csv");

    f.writeAsString(csv);

    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _generateCsvFile,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}