原文地址

#Installing（安裝）

Use this package as a library

Depend on it Add this to your package's pubspec.yaml file:

dependencies:sqflite: ^0.11.1 復制代碼

Install it You can install packages from the command line:

with Flutter:

$ flutter packages get 復制代碼

Alternatively, your editor might support flutter packages get. Check the docs for your editor to learn more.

Import it Now in your Dart code, you can use:

import 'package:sqflite/sqflite.dart';復制代碼

#整體介紹

##sqflite

SQLite plugin for Flutter. Supports both iOS and Android.

• Support transactions and batches

• Automatic version managment during open

• Helpers for insert/query/update/delete queries

• DB operation executed in a background thread on iOS and Android

Getting Started

In your flutter project add the dependency:

dependencies:...sqflite: ^0.11.1 復制代碼

For help getting started with Flutter, view the online documentation.

Usage example

Import sqflite.dart

import 'package:sqflite/sqflite.dart';

Raw SQL queries

Demo code to perform Raw SQL queries

// Get a location using getDatabasesPath var databasesPath = await getDatabasesPath(); String path = join(databasesPath, "demo.db");// Delete the database await deleteDatabase(path);// open the database Database database = await openDatabase(path, version: 1,onCreate: (Database db, int version) async {// When creating the db, create the tableawait db.execute("CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)"); });// Insert some records in a transaction await database.transaction((txn) async {int id1 = await txn.rawInsert('INSERT INTO Test(name, value, num) VALUES("some name", 1234, 456.789)');print("inserted1: $id1");int id2 = await txn.rawInsert('INSERT INTO Test(name, value, num) VALUES(?, ?, ?)',["another name", 12345678, 3.1416]);print("inserted2: $id2"); });// Update some record int count = await database.rawUpdate('UPDATE Test SET name = ?, VALUE = ? WHERE name = ?',["updated name", "9876", "some name"]); print("updated: $count");// Get the records List<Map> list = await database.rawQuery('SELECT * FROM Test'); List<Map> expectedList = [{"name": "updated name", "id": 1, "value": 9876, "num": 456.789},{"name": "another name", "id": 2, "value": 12345678, "num": 3.1416} ]; print(list); print(expectedList); assert(const DeepCollectionEquality().equals(list, expectedList));// Count the records count = Sqflite.firstIntValue(await database.rawQuery("SELECT COUNT(*) FROM Test")); assert(count == 2);// Delete a record count = await database.rawDelete('DELETE FROM Test WHERE name = ?', ['another name']); assert(count == 1);// Close the database await database.close(); 復制代碼

SQL helpers

Example using the helpers

final String tableTodo = "todo"; final String columnId = "_id"; final String columnTitle = "title"; final String columnDone = "done";class Todo {int id;String title;bool done;Map toMap() {Map map = {columnTitle: title, columnDone: done == true ? 1 : 0};if (id != null) {map[columnId] = id;}return map;}Todo();Todo.fromMap(Map map) {id = map[columnId];title = map[columnTitle];done = map[columnDone] == 1;} }class TodoProvider {Database db;Future open(String path) async {db = await openDatabase(path, version: 1,onCreate: (Database db, int version) async {await db.execute(''' create table $tableTodo ( $columnId integer primary key autoincrement, $columnTitle text not null,$columnDone integer not null) ''');});}Future<Todo> insert(Todo todo) async {todo.id = await db.insert(tableTodo, todo.toMap());return todo;}Future<Todo> getTodo(int id) async {List<Map> maps = await db.query(tableTodo,columns: [columnId, columnDone, columnTitle],where: "$columnId = ?",whereArgs: [id]);if (maps.length > 0) {return new Todo.fromMap(maps.first);}return null;}Future<int> delete(int id) async {return await db.delete(tableTodo, where: "$columnId = ?", whereArgs: [id]);}Future<int> update(Todo todo) async {return await db.update(tableTodo, todo.toMap(),where: "$columnId = ?", whereArgs: [todo.id]);}Future close() async => db.close(); } 復制代碼

Transaction

Don't use the database but only use the Transaction object in a transaction to access the database

await database.transaction((txn) async {// Okawait txn.execute("CREATE TABLE Test1 (id INTEGER PRIMARY KEY)");// DON'T use the database object in a transaction// this will deadlock!await database.execute("CREATE TABLE Test2 (id INTEGER PRIMARY KEY)"); }); 復制代碼

Batch support

To avoid ping-pong between dart and native code, you can use Batch:

batch = db.batch(); batch.insert("Test", {"name": "item"}); batch.update("Test", {"name": "new_item"}, where: "name = ?", whereArgs: ["item"]); batch.delete("Test", where: "name = ?", whereArgs: ["item"]); results = await batch.commit(); 復制代碼

Getting the result for each operation has a cost (id for insertion and number of changes for update and delete), especially on Android where an extra SQL request is executed. If you don't care about the result and worry about performance in big batches, you can use

await batch.commit(noResult: true);

Warning, during a transaction, the batch won't be commited until the transaction is commited

await database.transaction((txn) async {var batch = txn.batch();// ...// commit but the actual commit will happen when the transaction is commited// however the data is available in this transactionawait batch.commit();// ... }); 復制代碼

Table and column names

In general it is better to avoid using SQLite keywords for entity names. If any of the following name is used:

"add","all","alter","and","as","autoincrement","between","case","check","collate","commit","constraint","create","default","deferrable","delete","distinct","drop","else","escape","except","exists","foreign","from","group","having","if","in","index","insert","intersect","into","is","isnull","join","limit","not","notnull","null","on","or","order","primary","references","select","set","table","then","to","transaction","union","unique","update","using","values","when","where"復制代碼

the helper will escape the name i.e.

db.query("table")

will be equivalent to manually adding double-quote around the table name (confusingly here named table)

db.rawQuery('SELECT * FROM "table"'); 復制代碼

However in any other raw statement (including orderBy, where, groupBy), make sure to escape the name properly using double quote. For example see below where the column name group is not escaped in the columns argument, but is escaped in the where argument.

db.query("table", columns: ["group"], where: '"group" = ?', whereArgs: ["my_group"]); 復制代碼

Supported SQLite types

No validity check is done on values yet so please avoid non supported types. DateTime is not a supported SQL type (www.sqlite.org/datatype3.h…). Personally I store them as int (millisSinceEpoch) or string (iso8601)

INTEGER

Dart type: int

Supported values: from -2^63 to 2^63 - 1

REAL

Dart type: num

TEXT

Dart type: String

BLOB

Dart type: Uint8List

Dart type List is supported but not recommended (slow conversion)

Current issues

• Due to the way transaction works in SQLite (threads), concurrent read and write transaction are not supported. All calls are currently synchronized and transactions block are exclusive. I thought that a basic way to support concurrent access is to open a database multiple times but it only works on iOS as Android reuses the same database object. I also thought a native thread could be a potential future solution however on android accessing the database in another thread is blocked while in a transaction...

• Currently INTEGER are limited to -2^63 to 2^63 - 1 (although Android supports bigger ones)

More

How to guide

Example

import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'package:sqflite/sqflite.dart'; import 'package:sqflite_example/exp_test_page.dart'; import 'package:sqflite_example/deprecated_test_page.dart'; import 'model/main_item.dart'; import 'open_test_page.dart'; import 'package:sqflite_example/exception_test_page.dart'; import 'raw_test_page.dart'; import 'slow_test_page.dart'; import 'src/main_item_widget.dart'; import 'type_test_page.dart'; import 'todo_test_page.dart';void main() {runApp(new MyApp()); }class MyApp extends StatefulWidget {// This widget is the root of your application.@override_MyAppState createState() => new _MyAppState(); }const String testRawRoute = "/test/simple"; const String testOpenRoute = "/test/open"; const String testSlowRoute = "/test/slow"; const String testThreadRoute = "/test/thread"; const String testTodoRoute = "/test/todo"; const String testExceptionRoute = "/test/exception"; const String testExpRoute = "/test/exp"; const String testDeprecatedRoute = "/test/deprecated";class _MyAppState extends State<MyApp> {var routes = <String, WidgetBuilder>{'/test': (BuildContext context) => new MyHomePage(),testRawRoute: (BuildContext context) => new SimpleTestPage(),testOpenRoute: (BuildContext context) => new OpenTestPage(),testSlowRoute: (BuildContext context) => new SlowTestPage(),testTodoRoute: (BuildContext context) => new TodoTestPage(),testThreadRoute: (BuildContext context) => new TypeTestPage(),testExceptionRoute: (BuildContext context) => new ExceptionTestPage(),testExpRoute: (BuildContext context) => new ExpTestPage(),testDeprecatedRoute: (BuildContext context) => new DeprecatedTestPage(),};@overrideWidget build(BuildContext context) {return new MaterialApp(title: 'Sqflite Demo',theme: new 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 press Run > Hot Reload App in IntelliJ).// Notice that the counter didn't reset back to zero -- the application// is not restarted.primarySwatch: Colors.blue,),home: new MyHomePage(title: 'Sqflite Demo Home Page'),routes: routes);} }class MyHomePage extends StatefulWidget {final List<MainItem> items = [];MyHomePage({Key key, this.title}) : super(key: key) {items.add(new MainItem("Raw tests", "Raw SQLite operations",route: testRawRoute));items.add(new MainItem("Open tests", "Open onCreate/onUpgrade/onDowngrade",route: testOpenRoute));items.add(new MainItem("Type tests", "Test value types", route: testThreadRoute));items.add(new MainItem("Slow tests", "Lengthy operations", route: testSlowRoute));items.add(new MainItem("Todo database example", "Simple Todo-like database usage example",route: testTodoRoute));items.add(new MainItem("Exp tests", "Experimental and various tests",route: testExpRoute));items.add(new MainItem("Exception tests", "Tests that trigger exceptions",route: testExceptionRoute));items.add(new MainItem("Deprecated test","Keeping some old tests for deprecated functionalities",route: testDeprecatedRoute));// Uncomment to view all logs//Sqflite.devSetDebugModeOn(true);}// 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() => new _MyHomePageState(); }class _MyHomePageState extends State<MyHomePage> {String _platformVersion = 'Unknown';int get _itemCount => widget.items.length;@overrideinitState() {super.initState();initPlatformState();}// Platform messages are asynchronous, so we initialize in an async method.initPlatformState() async {String platformVersion;// Platform messages may fail, so we use a try/catch PlatformException.try {platformVersion = await Sqflite.platformVersion;} on PlatformException {platformVersion = "Failed to get platform version";}// If the widget was removed from the tree while the asynchronous platform// message was in flight, we want to discard the reply rather than calling// setState to update our non-existent appearance.if (!mounted) return;setState(() {_platformVersion = platformVersion;});print("running on: " + _platformVersion);}@overrideWidget build(BuildContext context) {return new Scaffold(appBar: new AppBar(title: new Center(child: new Text('Sqflite demo', textAlign: TextAlign.center)),),body: new ListView.builder(itemBuilder: _itemBuilder, itemCount: _itemCount));}//new Center(child: new Text('Running on: $_platformVersion\n')),Widget _itemBuilder(BuildContext context, int index) {return new MainItemWidget(widget.items[index], (MainItem item) {Navigator.of(context).pushNamed(item.route);});} } 復制代碼

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