flutter 文件操作与网络请求

flutter 文件操作与网络请求

文件操作

• APP 目录
  • 临时目录
    • getTemporaryDirectory()获取；系统可随时清除临时目录的文件；
  • 文档目录
    • getApplicationDocumentsDirectory()获取；只有当应用程序被卸载时，系统才会清除该目录
  • 外部存储目录
    • getExternalStorageDirectory()获取；
• 第三方库 path_provider，样例

import 'dart:io';
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';class FileOperationRoute extends StatefulWidget {FileOperationRoute({Key? key}) : super(key: key);@override_FileOperationRouteState createState() => _FileOperationRouteState();
}class _FileOperationRouteState extends State<FileOperationRoute> {int _counter = 0;@overridevoid initState() {super.initState();//从文件读取点击次数_readCounter().then((int value) {setState(() {_counter = value;});});}Future<File> _getLocalFile() async {// 获取应用目录String dir = (await getApplicationDocumentsDirectory()).path;return File('$dir/counter.txt');}Future<int> _readCounter() async {try {File file = await _getLocalFile();// 读取点击次数（以字符串）String contents = await file.readAsString</