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网站注册表单怎么做,金溪做网站,辽宁省营商建设监督局网站,临夏网站建设flutter开发实战-本地SQLite数据库存储 正在编写一个需要持久化且查询大量本地设备数据的 app#xff0c;可考虑采用数据库。相比于其他本地持久化方案来说#xff0c;数据库能够提供更为迅速的插入、更新、查询功能。这里需要用到sqflite package 来使用 SQLite 数据库 预…flutter开发实战-本地SQLite数据库存储 正在编写一个需要持久化且查询大量本地设备数据的 app可考虑采用数据库。相比于其他本地持久化方案来说数据库能够提供更为迅速的插入、更新、查询功能。这里需要用到sqflite package 来使用 SQLite 数据库 预览图
一、引入sqflite 在工程的pubspec.yaml中引入插件 # sqflitesqflite: ^2.2.84 二、使用sqflite 使用 sqflite 实现插入读取更新删除数据。 打开数据库 Futurevoid openDB(BuildContext context) async {// Open the database and store the reference.database await openDatabase(// Set the path to the database. Note: Using the join function from the// path package is best practice to ensure the path is correctly// constructed for each platform.join(await getDatabasesPath(), doggie_database.db),// When the database is first created, create a table to store dogs.onCreate: (db, version) {// Run the CREATE TABLE statement on the database.return db.execute(CREATE TABLE dogs(id INTEGER PRIMARY KEY, name TEXT, age INTEGER),);},version: 1,);} 插入一条记录 Futurevoid insertDB(BuildContext context) async {dogId;// Create a Dog and add it to the dogs tablevar fido Dog(id: dogId,name: Fido,age: 35,);// Get a reference to the database.final db await database;// Insert the Dog into the correct table. You might also specify the// conflictAlgorithm to use in case the same dog is inserted twice.//// In this case, replace any previous data.await db?.insert(dogs,fido.toMap(),conflictAlgorithm: ConflictAlgorithm.replace,);} 更新一条记录 Futurevoid updateDog(Dog dog) async {// Get a reference to the database.final db await database;// Update the given Dog.await db?.update(dogs,dog.toMap(),// Ensure that the Dog has a matching id.where: id ?,// Pass the Dogs id as a whereArg to prevent SQL injection.whereArgs: [dog.id],);} 删除一条记录 Futurevoid deleteDog(int id) async {// Get a reference to the database.final db await database;// Remove the Dog from the database.await db?.delete(dogs,// Use a where clause to delete a specific dog.where: id ?,// Pass the Dogs id as a whereArg to prevent SQL injection.whereArgs: [id],);} 获取存储记录 // A method that retrieves all the dogs from the dogs table.FutureListDog dogs() async {// Get a reference to the database.final db await database;// Query the table for all the dogs.final ListMapString, Object?? dogMaps await db?.query(dogs);if (dogMaps ! null dogMaps.isNotEmpty) {// Convert the list of each dogs fields into a list of Dog objects.ListDog dogs [];for(var dogMap in dogMaps) {// Dog dog Dog(id: dogMap[id]??0, name: name, age: age)var id dogMap[id] as int;var name dogMap[name] as String;var age dogMap[age] as int;Dog dog Dog(id: id, name: name, age: age);dogs.add(dog);}return dogs;}return [];} 完整代码如下 import package:flutter/material.dart; import dart:async;import package:flutter/widgets.dart; import package:path/path.dart; import package:sqflite/sqflite.dart;class SqliteDemoPage extends StatefulWidget {const SqliteDemoPage({super.key});overrideStateSqliteDemoPage createState() _SqliteDemoPageState(); }class _SqliteDemoPageState extends StateSqliteDemoPage {Database? database;int dogId 0;Futurevoid openDB(BuildContext context) async {// Open the database and store the reference.database await openDatabase(// Set the path to the database. Note: Using the join function from the// path package is best practice to ensure the path is correctly// constructed for each platform.join(await getDatabasesPath(), doggie_database.db),// When the database is first created, create a table to store dogs.onCreate: (db, version) {// Run the CREATE TABLE statement on the database.return db.execute(CREATE TABLE dogs(id INTEGER PRIMARY KEY, name TEXT, age INTEGER),);},version: 1,);}// A method that retrieves all the dogs from the dogs table.FutureListDog dogs() async {// Get a reference to the database.final db await database;// Query the table for all the dogs.final ListMapString, Object?? dogMaps await db?.query(dogs);if (dogMaps ! null dogMaps.isNotEmpty) {// Convert the list of each dogs fields into a list of Dog objects.ListDog dogs [];for(var dogMap in dogMaps) {// Dog dog Dog(id: dogMap[id]??0, name: name, age: age)var id dogMap[id] as int;var name dogMap[name] as String;var age dogMap[age] as int;Dog dog Dog(id: id, name: name, age: age);dogs.add(dog);}return dogs;}return [];}Futurevoid updateDog(Dog dog) async {// Get a reference to the database.final db await database;// Update the given Dog.await db?.update(dogs,dog.toMap(),// Ensure that the Dog has a matching id.where: id ?,// Pass the Dogs id as a whereArg to prevent SQL injection.whereArgs: [dog.id],);}Futurevoid deleteDog(int id) async {// Get a reference to the database.final db await database;// Remove the Dog from the database.await db?.delete(dogs,// Use a where clause to delete a specific dog.where: id ?,// Pass the Dogs id as a whereArg to prevent SQL injection.whereArgs: [id],);}Futurevoid insertDB(BuildContext context) async {dogId;// Create a Dog and add it to the dogs tablevar fido Dog(id: dogId,name: Fido,age: 35,);// Get a reference to the database.final db await database;// Insert the Dog into the correct table. You might also specify the// conflictAlgorithm to use in case the same dog is inserted twice.//// In this case, replace any previous data.await db?.insert(dogs,fido.toMap(),conflictAlgorithm: ConflictAlgorithm.replace,);}Futurevoid getListFromDB(BuildContext context) async {ListDog list await dogs();for(var dog in list) {print(dog info:\({dog.toString()});}}void updateDB(BuildContext context) {var dog Dog(id: dogId,name: AFarah,age: 11,);updateDog(dog);}Futurevoid deleteDB(BuildContext context) async {await deleteDog(dogId);dogId--;}overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(title: const Text(SqliteDemo),),body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [const SizedBox(height: 20,),TextButton(onPressed: () {openDB(context);},child: Container(height: 36,width: 200,color: Colors.lightGreen,alignment: Alignment.center,child: const Text(openDatabase,style: TextStyle(fontSize: 12, color: Colors.white),),),),const SizedBox(height: 20,),TextButton(onPressed: () {insertDB(context);},child: Container(height: 36,width: 200,color: Colors.lightGreen,alignment: Alignment.center,child: const Text(插入一条dog记录,style: TextStyle(fontSize: 12, color: Colors.white),),),),const SizedBox(height: 20,),TextButton(onPressed: () {getListFromDB(context);},child: Container(height: 36,width: 200,color: Colors.lightGreen,alignment: Alignment.center,child: const Text(获取记录列表,style: TextStyle(fontSize: 12, color: Colors.white),),),),const SizedBox(height: 20,),TextButton(onPressed: () {updateDB(context);},child: Container(height: 36,width: 200,color: Colors.lightGreen,alignment: Alignment.center,child: const Text(更新一条记录,style: TextStyle(fontSize: 12, color: Colors.white),),),),const SizedBox(height: 20,),TextButton(onPressed: () {deleteDB(context);},child: Container(height: 36,width: 200,color: Colors.lightGreen,alignment: Alignment.center,child: const Text(删除一条记录,style: TextStyle(fontSize: 12, color: Colors.white),),),),],),),);} }class Dog {final int id;final String name;final int age;const Dog({required this.id,required this.name,required this.age,});// Convert a Dog into a Map. The keys must correspond to the names of the// columns in the database.MapString, Object? toMap() {return {id: id,name: name,age: age,};}// Implement toString to make it easier to see information about// each dog when using the print statement.overrideString toString() {return Dog{id: \)id, name: \(name, age: \)age};} } 三、小结 flutter开发实战-本地SQLite数据库存储 学习记录每天不停进步。