如何在flutter中获取.db文件或文件路径? [英] How can I get my .db file or filepath in flutter?

问题描述

我已将一些信息还原到名为"cities.db"的文件中，并将其放在项目路径"/assets"中，您能告诉我如何获取它吗?

I have restored some information in a file named "cities.db", and I put it in project path "/assets", could you tell me how to get it?

安装该应用程序后，可以在路径"/data/data/pkgName/code_cache/xxx/xxx/build/flutter_assets/assets/cities.db"中找到该文件.

After I have installed the app, I can find the file in path "/data/data/pkgName/code_cache/xxx/xxx/build/flutter_assets/assets/cities.db".

如果我使用这种方法，

 var databasesPath = await getDatabasesPath();
 String path = join(databasesPath, 'cities.db');
 Database _db = await openDatabase(_path);

我可以在路径"/data/data/pkgName/databases/"中找到一个空的数据库文件

I can find an empty db file in path "/data/data/pkgName/databases/"

推荐答案

如果将db文件放在资产目录中，则必须使用rootBundle

If you put yours db file in assets directory, you have to use rootBundle

ByteData data = await rootBundle.load(join('assets', 'cities.db'));
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
print("${bytes}");

有关加载和写入的进一步详细过程assests/your_localdb，请参考此
SQLite扑朔迷离，数据库资产如何工作

For further detail process assests/your_localdb, about load and write please reference this
Sqlite in flutter, how database assets work

使用rootBundle的完整代码.

full code to use rootBundle.

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart';
import 'dart:async' show Future;
import 'package:flutter/services.dart' show rootBundle;
import 'dart:typed_data';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

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

  void _incrementCounter() async{
    ByteData data = await rootBundle.load(join('assets', 'cities.db'));
    List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
    print("${bytes}");

    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

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