blocks|key|2301453|text|更新2020+-+05+-+15|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2301454|这将不起作用，请参阅：|2301455|2301456|Unable+to+call+a+platform+channel+method+from+another+isolate+·+Issue+#13937+·+flutter/flutter|unordered-list-item|offset|length|2301457|2301458|2301459|注意:完整的代码可以在末尾找到|2301460|​|2301461|📷|atomic|2301462|2301463|步骤1:使你的方法成为静态的，并使它无效|2301464|++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();
++++}
++}|code-block|syntax|javascript|2301465|步骤2:创建新方法(通常但不是必需的，添加同名的异步)|2301466|++Future+batchInsertEventSongAsync(List<EventSong>+rows)+{

++}|2301467|第3步:使用您的方法static调用计算并返回|2301468|++return+compute(batchInsertEventSong,+rows);|2301469|2301470|步骤1、2、3代码评审|2301471|++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();
++++}
++}|2301472|2301473|完整代码|2301474|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%2B%2B)+{
++++++rows.add(EventSong(i));
++++++print("fetching+raws+"+%2B+(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%2B%2B)+{
++++++print("saving+raws+"+%2B+(i+/+rows.length).toString());
++++}
++}
}

class+EventSong+{
++int+id;
++EventSong(this.id);
}|2301475|参考：|2301476|2301477|Parse+JSON+in+the+background+-+Flutter|2301478|2301479|不重要的参考：|2301480|2301481|Flutter+async+:+Beginner+friendly+guide+for+heavy+lifting+operations|2301482|2301483|2301484|Dart/Flutter+:+Converting+timestamp+-+Stack+Overflow|2301485|2301486|2301487|Display+a+snackbar+-+Flutter|2301488|2301489|2301490|sdk/file.dart+at+1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb+·+dart-lang/sdk|2301491|2301492|2301493|Search+·+openSync(){|2301494|2301495|2301496|sdk/file_impl.dart+at+1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb+·+dart-lang/sdk|2301497|2301498|2301499|Search+·+readAsLinesSync|2301500|2301501|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/flutter/flutter/issues/13937|1|IMAGE|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/247b09b602bd068247c8bb13d9e0a351.gif|imageAlt|2|https://flutter.dev/docs/cookbook/networking/background-parsing#4-move-this-work-to-a-separate-isolate|3|https://blog.usejournal.com/flutter-async-beginner-friendly-guide-for-heavy-lifting-operations-cf8ec81833d7?gi=c61a4a7f641d|4|https://stackoverflow.com/questions/50632217/dart-flutter-converting-timestamp|5|https://flutter.dev/docs/cookbook/design/snackbars|6|https://github.com/dart-lang/sdk/blob/1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb/sdk/lib/io/file.dart|7|https://github.com/dart-lang/sdk/search?p=3&q=openSync%2528%2529%257B&unscoped_q=openSync%2528%2529%257B|8|https://github.com/dart-lang/sdk/blob/1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb/sdk/lib/io/file_impl.dart|9|https://github.com/dart-lang/sdk/search?p=3&q=readAsLinesSync&unscoped_q=readAsLinesSync^0|0|0|0|0|2M|0|0|0|0|0|0|0|1|1|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|12|2|0|0|0|0|0|1W|3|0|0|0|0|1G|4|0|0|0|0|S|5|0|0|0|0|21|6|0|0|0|0|K|7|0|0|0|0|26|8|0|0|0|0|O|9|0|0^^$0|@$1|2|3|4|5|6|7|3C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|3D|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|3E|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|3F|8|@]|9|@$H|3G|I|3H|1|3I]]|A|$]]|$1|J|3|-4|5|6|7|3J|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|3K|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|3L|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|3M|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|3N|8|@]|9|@$H|3O|I|3P|1|3Q]]|A|$]]|$1|S|3|O|5|6|7|3R|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|3S|8|@]|9|@]|A|$]]|$1|V|3|W|5|X|7|3T|8|@]|9|@]|A|$Y|Z]]|$1|10|3|11|5|6|7|3U|8|@]|9|@]|A|$]]|$1|12|3|13|5|X|7|3V|8|@]|9|@]|A|$Y|Z]]|$1|14|3|15|5|6|7|3W|8|@]|9|@]|A|$]]|$1|16|3|17|5|X|7|3X|8|@]|9|@]|A|$Y|Z]]|$1|18|3|-4|5|6|7|3Y|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|3Z|8|@]|9|@]|A|$]]|$1|1B|3|1C|5|X|7|40|8|@]|9|@]|A|$Y|Z]]|$1|1D|3|-4|5|6|7|41|8|@]|9|@]|A|$]]|$1|1E|3|1F|5|6|7|42|8|@]|9|@]|A|$]]|$1|1G|3|1H|5|X|7|43|8|@]|9|@]|A|$Y|Z]]|$1|1I|3|1J|5|6|7|44|8|@]|9|@]|A|$]]|$1|1K|3|-4|5|6|7|45|8|@]|9|@]|A|$]]|$1|1L|3|1M|5|G|7|46|8|@]|9|@$H|47|I|48|1|49]]|A|$]]|$1|1N|3|-4|5|6|7|4A|8|@]|9|@]|A|$]]|$1|1O|3|1P|5|6|7|4B|8|@]|9|@]|A|$]]|$1|1Q|3|-4|5|6|7|4C|8|@]|9|@]|A|$]]|$1|1R|3|1S|5|G|7|4D|8|@]|9|@$H|4E|I|4F|1|4G]]|A|$]]|$1|1T|3|-4|5|6|7|4H|8|@]|9|@]|A|$]]|$1|1U|3|-4|5|6|7|4I|8|@]|9|@]|A|$]]|$1|1V|3|1W|5|G|7|4J|8|@]|9|@$H|4K|I|4L|1|4M]]|A|$]]|$1|1X|3|-4|5|6|7|4N|8|@]|9|@]|A|$]]|$1|1Y|3|-4|5|6|7|4O|8|@]|9|@]|A|$]]|$1|1Z|3|20|5|G|7|4P|8|@]|9|@$H|4Q|I|4R|1|4S]]|A|$]]|$1|21|3|-4|5|6|7|4T|8|@]|9|@]|A|$]]|$1|22|3|-4|5|6|7|4U|8|@]|9|@]|A|$]]|$1|23|3|24|5|G|7|4V|8|@]|9|@$H|4W|I|4X|1|4Y]]|A|$]]|$1|25|3|-4|5|6|7|4Z|8|@]|9|@]|A|$]]|$1|26|3|-4|5|6|7|50|8|@]|9|@]|A|$]]|$1|27|3|28|5|G|7|51|8|@]|9|@$H|52|I|53|1|54]]|A|$]]|$1|29|3|-4|5|6|7|55|8|@]|9|@]|A|$]]|$1|2A|3|-4|5|6|7|56|8|@]|9|@]|A|$]]|$1|2B|3|2C|5|G|7|57|8|@]|9|@$H|58|I|59|1|5A]]|A|$]]|$1|2D|3|-4|5|6|7|5B|8|@]|9|@]|A|$]]|$1|2E|3|-4|5|6|7|5C|8|@]|9|@]|A|$]]|$1|2F|3|2G|5|G|7|5D|8|@]|9|@$H|5E|I|5F|1|5G]]|A|$]]|$1|2H|3|-4|5|6|7|5H|8|@]|9|@]|A|$]]|$1|2I|3|-4|5|6|7|5I|8|@]|9|@]|A|$]]]|2J|$2K|$5|2L|2M|2N|A|$2O|2P]]|2Q|$5|2R|2M|2S|A|$2T|2U|2V|-4]]|2W|$5|2L|2M|2N|A|$2O|2X]]|2Y|$5|2L|2M|2N|A|$2O|2Z]]|30|$5|2L|2M|2N|A|$2O|31]]|32|$5|2L|2M|2N|A|$2O|33]]|34|$5|2L|2M|2N|A|$2O|35]]|36|$5|2L|2M|2N|A|$2O|37]]|38|$5|2L|2M|2N|A|$2O|39]]|3A|$5|2L|2M|2N|A|$2O|3B]]]]

<h2>Update 2020 - 05 - 15</h2>
<h3>this will not work see :</h3>
<ul>
<li><a href="https://github.com/flutter/flutter/issues/13937" rel="nofollow noreferrer">Unable to call a platform channel method from another isolate · Issue #13937 · flutter/flutter</a></li>
</ul>
<hr />
<h2>Note : full code available on the end</h2>
<p><a href="https://i.stack.imgur.com/tM7EC.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tM7EC.gif" alt="gif of the working sampe app" /></a></p>
<h2>Step 1 : make your method static and make it void</h2>
<pre class="lang-dart prettyprint-override"><code>  static batchInsertEventSong(List&lt;EventSong&gt; rows) {
    Database db = await instance.database;
    db.transaction((txn) async {
        Batch batch = txn.batch();
        for (var song in rows) {
            Map&lt;String, dynamic&gt; row = {
            DatabaseHelper.columnIdSong: song.id,
            DatabaseHelper.columnTitle: song.title,
            DatabaseHelper.columnInterpreter: song.interpreter
            };
            batch.insert(table, row);
        }
        batch.commit();
    }
  }
</code></pre>
<h2>Step 2 : create new method (usually but not required add Async for the same name)</h2>
<pre class="lang-dart prettyprint-override"><code>  Future batchInsertEventSongAsync(List&lt;EventSong&gt; rows) {

  }
</code></pre>
<h2>Step 3 : call compute with  your method static and return</h2>
<pre class="lang-dart prettyprint-override"><code>  return compute(batchInsertEventSong, rows);
</code></pre>
<hr />
<h3>Step [1,2,3] code review</h3>
<pre class="lang-dart prettyprint-override"><code>  Future batchInsertEventSongAsync(List&lt;EventSong&gt; rows) {
    return compute(_batchInsertEventSong, rows);
  }

  static _batchInsertEventSong(List&lt;EventSong&gt; rows) {
    Database db = await instance.database;
    db.transaction((txn) async {
        Batch batch = txn.batch();
        for (var song in rows) {
            Map&lt;String, dynamic&gt; row = {
            DatabaseHelper.columnIdSong: song.id,
            DatabaseHelper.columnTitle: song.title,
            DatabaseHelper.columnInterpreter: song.interpreter
            };
            batch.insert(table, row);
        }
        batch.commit();
    }
  }
</code></pre>
<hr />
<h2>Full Code</h2>
<pre class="lang-dart prettyprint-override"><code>import 'dart:async';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

void main() =&gt; 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() =&gt; _MyHomePageState();
}

class _MyHomePageState extends State&lt;MyHomePage&gt; {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: &lt;Widget&gt;[
            FlatButton.icon(
              icon: Icon(Icons.backup),
              label: Text(&quot;Long Opreation&quot;),
              onPressed: () async {
                var rows = await RsetApi.getRawsAsync();
                await Database._saveRaws(rows);
              },
            ),
            FlatButton.icon(
              icon: Icon(Icons.backup),
              label: Text(&quot;Short Opreation&quot;),
              onPressed: () {
                Scaffold.of(context).hideCurrentSnackBar();
                Scaffold.of(context).showSnackBar(new SnackBar(
                  content: new Text(DateTime.now().toIso8601String()),
                ));
              },
            ),
          ],
        ),
      ),
    );
  }
}

class RsetApi {
  static Future&lt;List&lt;EventSong&gt;&gt; getRawsAsync() {
    return compute(_getRaws, null);
  }

  static List&lt;EventSong&gt; _getRaws(pram1) {
    var rows = List&lt;EventSong&gt;();
    for (var i = 1; i &lt; 12000; i++) {
      rows.add(EventSong(i));
      print(&quot;fetching raws &quot; + (i / 12000).toString());
    }
    return rows;
  }
}

class Database {
  static Future saveRawsAsync(List&lt;EventSong&gt; rows) {
    return compute(_saveRaws, rows);
  }

  static _saveRaws(List&lt;EventSong&gt; rows) {
    for (var i = 1; i &lt; rows.length; i++) {
      print(&quot;saving raws &quot; + (i / rows.length).toString());
    }
  }
}

class EventSong {
  int id;
  EventSong(this.id);
}
</code></pre>
<h2>Ref:</h2>
<ul>
<li><a href="https://flutter.dev/docs/cookbook/networking/background-parsing#4-move-this-work-to-a-separate-isolate" rel="nofollow noreferrer">Parse JSON in the background - Flutter</a></li>
</ul>
<h2>non-important Ref:</h2>
<ul>
<li><p><a href="https://blog.usejournal.com/flutter-async-beginner-friendly-guide-for-heavy-lifting-operations-cf8ec81833d7?gi=c61a4a7f641d" rel="nofollow noreferrer">Flutter async : Beginner friendly guide for heavy lifting operations</a></p>
</li>
<li><p><a href="https://stackoverflow.com/questions/50632217/dart-flutter-converting-timestamp">Dart/Flutter : Converting timestamp - Stack Overflow</a></p>
</li>
<li><p><a href="https://flutter.dev/docs/cookbook/design/snackbars" rel="nofollow noreferrer">Display a snackbar - Flutter</a></p>
</li>
<li><p><a href="https://github.com/dart-lang/sdk/blob/1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb/sdk/lib/io/file.dart" rel="nofollow noreferrer">sdk/file.dart at 1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb · dart-lang/sdk</a></p>
</li>
<li><p><a href="https://github.com/dart-lang/sdk/search?p=3&amp;q=openSync%28%29%7B&amp;unscoped_q=openSync%28%29%7B" rel="nofollow noreferrer">Search · openSync(){</a></p>
</li>
<li><p><a href="https://github.com/dart-lang/sdk/blob/1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb/sdk/lib/io/file_impl.dart" rel="nofollow noreferrer">sdk/file_impl.dart at 1c4ad14fa3a0a1d5ecea10e3b04befecee3ffbcb · dart-lang/sdk</a></p>
</li>
<li><p><a href="https://github.com/dart-lang/sdk/search?p=3&amp;q=readAsLinesSync&amp;unscoped_q=readAsLinesSync" rel="nofollow noreferrer">Search · readAsLinesSync</a></p>
</li>
</ul>


<p>I'm trying to insert a lot of rows (about 12k or more) in a sqlite memory database using flutter.</p>

<p>I get data from the API and use a compute function in order to process data from Json.
Now I need to add these data to a database in memory, in order to do so I use a transaction with a batch.</p>

<pre class="lang-dart prettyprint-override"><code>batchInsertEventSong(List&lt;EventSong&gt; rows) async {
   Database db = await instance.database;
   db.transaction((txn) async {
      Batch batch = txn.batch();
      for (var song in rows) {
         Map&lt;String, dynamic&gt; row = {
           DatabaseHelper.columnIdSong: song.id,
           DatabaseHelper.columnTitle: song.title,
           DatabaseHelper.columnInterpreter: song.interpreter
         };
         batch.insert(table, row);
       }
      batch.commit();
   }
}
</code></pre>

<p>But this function is blocking my UI during insertions, I tried also with compute but I can't pass the class db or the class batch.
I hadn't clear how to execute this process in another thread or (since I can't use isolates) executing without blocking my UI.</p>

<p>Any advice?</p>


Insert sqlite flutter without freezing the interface

数据库

Flutter

我正在尝试使用flutter在sqlite内存数据库中插入很多行(大约12k或更多)。我从API获取数据，并使用计算函数来处理来自Json的数据。现在，我需要将这些数据添加到内存中的数据库中，为此，我使用了一个带批处理的事务。batchInsertEventSong(List<EventSong> rows) asyn...

问在不冻结界面的情况下插入sqlite flutter
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