Flutter sqflite: Database unstable after hot reload

问题

I have the following code

  Future<InitData> getInitialData() async {
    print('OPENING');
    await open();
    print('DB = $_db ${_db.isOpen}');
    final rawDayActionTypes = await _db.query(...);

Where function open is the following

  Future<Database> open() async {
    if (_db != null && _db.isOpen) {
      return _db;
    }

    final dbPath = await sql.getDatabasesPath();
    final myDBPath = path.join(dbPath, db_name);
    _db = await sql.openDatabase(myDBPath, onCreate: _onCreateDB, version: 1);
    return _db;
  }

But after a hot reload, I get often the following error:

I/flutter (10806): DB = 1161 <db_name>.db true
E/flutter (10806): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: DatabaseException(error database_closed)
E/flutter (10806): #0      SqfliteDatabaseMixin.checkNotClosed 
package:sqflite_common/src/database_mixin.dart:282
E/flutter (10806): #1      SqfliteDatabaseExecutorMixin._rawQuery 
package:sqflite_common/src/database_mixin.dart:125
E/flutter (10806): #2      SqfliteDatabaseExecutorMixin.query 
package:sqflite_common/src/database_mixin.dart:110
E/flutter (10806): #3      DBService.getInitialData 
package:productive_diary/db/db_service.dart:56
E/flutter (10806): <asynchronous suspension>
E/flutter (10806): #4      _InitDBDataState._fetchData 
package:productive_diary/initScreen.dart:53
E/flutter (10806): #5      _InitDBDataState.didChangeDependencies

As you can see the DB was open (DB = 1161 <db_name>.db true)
on the line before executing the query(await _db.query(...);)

If you need to know what _InitDBDataState is doing in order to understand the context of the error,
you can check this related question

回答1:

sqflite supports hot-restart by finding the opened database if any (i.e. the dart side restarts but the native database is still open). hot-reload should not cause any issue.

The only thing I could think off is if you have a _db.close() call somewhere. In a typical one database scenario you should simply open the database on start and never close it.

If you are in this scenario, can ensure that close() is never called? (and try to comment this code)

来源：https://stackoverflow.com/questions/61599995/flutter-sqflite-database-unstable-after-hot-reload

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