Flutter入门系列-Flutter读取assets文件并写入应用程序路径

一、思考

 在Android开发中经常会遇到需要将asset中的文件拷贝到本地目录中，所以Flutter 是否有能够读取 asset 中文件的API呢？rootBundle 就可以解决该问题。 

二、代码

flutter:

  uses-material-design: true

  assets:
    - images/lovely_girl.jpg
    - images/travel_model.json
    - images/hello.json

import 'dart:convert';
import 'dart:developer';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:path_provider/path_provider.dart';

class RootBundlePage extends StatefulWidget {
  const RootBundlePage({Key? key}) : super(key: key);

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

class _RootBundlePageState extends State<RootBundlePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('RootBundle'),),
      body: Container(
        child: Column(
          children: [
            MaterialButton(onPressed:readDataFromBundle, child: Text('读入数据'),),
            MaterialButton(onPressed:readAndWriteImage, child: Text('读入图片并写入到指定文件'),),
          ],
        ),
      ),
    );
  }

  void readDataFromBundle() async {
    String data =  await rootBundle.loadString("images/hello.json");
    log("readDataFromBundle $data");
    var mapData = json.decode(data);
    Person person = Person.from(mapData);
    log("${person.name}");
  }

  void readAndWriteImage() async {
    String fileName = "lovely_girl.jpg";
    var bytes = await rootBundle.load("images/lovely_girl.jpg");
    String dir = (await getApplicationSupportDirectory()).path;
    String filePath = "$dir/$fileName";
    ByteBuffer buffer =  bytes.buffer;
    File file = await new File(filePath).writeAsBytes(buffer.asUint8List(bytes.offsetInBytes,
        bytes.lengthInBytes));
    log("readAndWriteImage ${file.path}");
    //[log] readAndWriteImage /data/user/0/com.example.flutter_widgets/files/lovely_girl.jpg
    // /data/data/com.example.flutter_widgets/files/lovely_girl.jpg
  }

}

//{"name": "lisi", "age": 20, "address": "beijing", "gender":"male"}
class Person{
  String? name;
  int? age;
  String? address;
  String? gender;

  Person(this.name, this.age, this.address, this.gender);

  Person.from(Map<String, dynamic> json){
    this.name = json['name'];
    this.age = json['age'];
    this.address = json['address'];
    this.gender = json['gender'];
  }

  Map<String, dynamic> toJson(){
    Map<String, dynamic> data = new Map<String, dynamic>();
    data['name'] = this.name;
    data['age'] = this.age;
    data['address'] = this.address;
    data['gender'] = this.gender;
    return data;
  }

}

参考：

Flutter读取assets文件并写入应用程序路径 - 简书