更新2020 - 05 - 15

这将不起作用，请参阅：

• Unable to call a platform channel method from another isolate · Issue #13937 · flutter/flutter

注意：完整代码在最后提供

x1c 0d1x的数据

第一步：将方法设为静态并设为void

static batchInsertEventSong(List<EventSong> rows) {
    Database db = await instance.database;
    db.transaction((txn) async {
        Batch batch = txn.batch();
        for (var song in rows) {
            Map<String, dynamic> row = {
            DatabaseHelper.columnIdSong: song.id,
            DatabaseHelper.columnTitle: song.title,
            DatabaseHelper.columnInterpreter: song.interpreter
            };
            batch.insert(table, row);
        }
        batch.commit();
    }
  }

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第二步：创建新方法（通常情况下，但不是必须的，为相同的名称添加Async）

Future batchInsertEventSongAsync(List<EventSong> rows) {

  }

型

第三步：使用方法static调用compute并返回

return compute(batchInsertEventSong, rows);

型

Step [1，2，3] code review

Future batchInsertEventSongAsync(List<EventSong> rows) {
    return compute(_batchInsertEventSong, rows);
  }

  static _batchInsertEventSong(List<EventSong> rows) {
    Database db = await instance.database;
    db.transaction((txn) async {
        Batch batch = txn.batch();
        for (var song in rows) {
            Map<String, dynamic> row = {
            DatabaseHelper.columnIdSong: song.id,
            DatabaseHelper.columnTitle: song.title,
            DatabaseHelper.columnInterpreter: song.interpreter
            };
            batch.insert(table, row);
        }
        batch.commit();
    }
  }

型

完整代码

import 'dart:async';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

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(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(body: 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> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FlatButton.icon(
              icon: Icon(Icons.backup),
              label: Text("Long Opreation"),
              onPressed: () async {
                var rows = await RsetApi.getRawsAsync();
                await Database._saveRaws(rows);
              },
            ),
            FlatButton.icon(
              icon: Icon(Icons.backup),
              label: Text("Short Opreation"),
              onPressed: () {
                Scaffold.of(context).hideCurrentSnackBar();
                Scaffold.of(context).showSnackBar(new SnackBar(
                  content: new Text(DateTime.now().toIso8601String()),
                ));
              },
            ),
          ],
        ),
      ),
    );
  }
}

class RsetApi {
  static Future<List<EventSong>> getRawsAsync() {
    return compute(_getRaws, null);
  }

  static List<EventSong> _getRaws(pram1) {
    var rows = List<EventSong>();
    for (var i = 1; i < 12000; i++) {
      rows.add(EventSong(i));
      print("fetching raws " + (i / 12000).toString());
    }
    return rows;
  }
}

class Database {
  static Future saveRawsAsync(List<EventSong> rows) {
    return compute(_saveRaws, rows);
  }

  static _saveRaws(List<EventSong> rows) {
    for (var i = 1; i < rows.length; i++) {
      print("saving raws " + (i / rows.length).toString());
    }
  }
}

class EventSong {
  int id;
  EventSong(this.id);
}

型

参考：

• 在后台解析JSON- Flutter

非重要参考：

• Flutter async : Beginner friendly guide for heavy lifting operations的
• Dart/Flutter : Converting timestamp - Stack Overflow的
• Display a snackbar - Flutter
• sdk/file.dart at 1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb · dart-lang/sdk
• Search · openSync(){
• sdk/file_impl.dart at 1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb · dart-lang/sdk
• Search · readAsLinesSync

首先，你应该在主线程中运行你的代码，而不是使用计算。Sqflite已经在自己的线程中运行，隔离支持有点复杂（因为你需要在隔离中打开数据库...）
其次，你应该等待提交（如果你启用了lint unawaited_futures，你实际上应该得到一个警告）。
如果你的for循环持续了2秒，那么无论你做什么，都会冻结UI，所以你应该分成更小的批处理（比如100个）。
这应该是一个可能的解决方案：

await db.transaction((txn) async {
  var batch = txn.batch();

  Future<void> commitBatch() async {
    if (batch.length > 0) {
      await batch.commit();
    }
  }

  // Commit existing and start a new batch
  Future<void> commitBatchAndRestart() async {
    await commitBatch();
    batch = txn.batch();
  }

  for (var song in rows) {
    var row = <String, Object?>{
      DatabaseHelper.columnIdSong: song.id,
      DatabaseHelper.columnTitle: song.title,
      DatabaseHelper.columnInterpreter: song.interpreter
    };
    batch.insert(table, row);
    // Commit every 100 items
    if (batch.length > 100) {
      await commitBatchAndRestart();
    }
  }
  // Commit the remaining items if needed
  await commitBatch();
});

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