实时计算记录和 return 总记录数,然后将其显示为小部件中的文本
Count records and return total records number in real time then display it as text in a widget
我正在尝试获取名为 'persons' 的 sqlite 数据库 table 的记录总数。获得记录总数后,我想在 Text()
小部件内的 Container
小部件中显示此数字。我尝试了不同的方法来完成这项工作,但我使用的任何方法都不起作用。
下面是db_helper.dart文件。需要 return 记录总数的函数被定义为 countPeople
.
import 'dart:async';
import 'dart:io' as io;
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
/// models
import 'package:path/path.dart';
class DBHelper {
static Database db_instance;
Future<Database> get db async {
if (db_instance == null) {
db_instance = await initDB();
}
return db_instance;
}
initDB() async {
var databasesPath = await getDatabasesPath();
String path = join(databasesPath, 'development.db');
var db = await openDatabase(path, version: 1, onCreate: onCreateFunc);
return db;
}
void onCreateFunc(Database db, int version) async {
// create table
await db.execute('''CREATE TABLE persons(
id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, nickname TEXT, country_id INTEGER, role TEXT, created DATETIME, updated DATETIME
);''');
}
/**
* crud functions
*/
void countPeople() async {
var db_connection = await db;
final count = Sqflite.firstIntValue(
await db_connection.rawQuery('SELECT COUNT(*) FROM persons'));
// assert(count == 2);
print('people count: $count');
}
Future<List<Person>> getAllPersons() async {
final db_connection = await db;
var response = await db_connection
.rawQuery("SELECT * FROM persons ORDER BY created DESC");
// print(response);
List<Person> list = response.map((c) => Person.fromJson(c)).toList();
return list;
}
// add new person
void addNewPerson(Person person) async {
var db_connection = await db;
String query = """
INSERT INTO persons(name,nickname,role,created,updated) VALUES('${person.name}','${person.nickname}', '${person.role}','${person.created}', '${person.updated}')
""";
await db_connection.transaction((transaction) async {
// print(query);
return await transaction.rawInsert(query);
});
}
下面是people_count.dart文件。这是我希望在 Text()
小部件中显示总记录数的地方。
import 'package:flutter/material.dart';
import 'package:com.example.simple_app/utils/db_helper.dart';
import 'package:com.example.simple_app/models/person.dart';
import 'package:com.example.simple_app/pages/main_user_registration/create_account.dart';
class MainUserRegistration extends StatefulWidget {
MainUserRegistration({Key key}) : super(key: key);
@override
_MainUserRegistrationState createState() => _MainUserRegistrationState();
}
var dbHelper = DBHelper();
class _MainUserRegistrationState extends State<MainUserRegistration> {
var result = dbHelper.countPeople();
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text('Loans'),
),
body: new Container(
child: Row(
children: <Widget>[
Text('all persons: ${dbHelper.countPeople()}'), // the total number of records should appear here
],
),
),
);
}
}
您可能应该尝试使用 setState()
来更改 initState
上的异步数据,这是 people_count.dart
的样子:
import 'package:flutter/material.dart';
import 'package:com.example.simple_app/utils/db_helper.dart';
import 'package:com.example.simple_app/models/person.dart';
import 'package:com.example.simple_app/pages/main_user_registration/create_account.dart';
class MainUserRegistration extends StatefulWidget {
MainUserRegistration({Key key}) : super(key: key);
@override
_MainUserRegistrationState createState() => _MainUserRegistrationState();
}
var dbHelper = DBHelper();
class _MainUserRegistrationState extends State<MainUserRegistration> {
int number = -1;
void countPeople() async {
int count = await dbHelper.countPeople();
setState(() => number = count);
@override
void initState() {
super.initState();
countPeople();
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text('Money Lender'),
),
body: new Container(
child: Row(
children: <Widget>[
Text('all persons: ${number}'), // the total number of records should appear here
],
),
),
);
}
}
而db_helper.dart中的人数统计函数应该return人数:
Future<int>countPeople() async {
var db_connection = await db;
final count = Sqflite.firstIntValue(
await db_connection.rawQuery('SELECT COUNT(*) FROM persons'));
// assert(count == 2);
print('people count: $count');
return count;
}
我正在尝试获取名为 'persons' 的 sqlite 数据库 table 的记录总数。获得记录总数后,我想在 Text()
小部件内的 Container
小部件中显示此数字。我尝试了不同的方法来完成这项工作,但我使用的任何方法都不起作用。
下面是db_helper.dart文件。需要 return 记录总数的函数被定义为 countPeople
.
import 'dart:async';
import 'dart:io' as io;
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
/// models
import 'package:path/path.dart';
class DBHelper {
static Database db_instance;
Future<Database> get db async {
if (db_instance == null) {
db_instance = await initDB();
}
return db_instance;
}
initDB() async {
var databasesPath = await getDatabasesPath();
String path = join(databasesPath, 'development.db');
var db = await openDatabase(path, version: 1, onCreate: onCreateFunc);
return db;
}
void onCreateFunc(Database db, int version) async {
// create table
await db.execute('''CREATE TABLE persons(
id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, nickname TEXT, country_id INTEGER, role TEXT, created DATETIME, updated DATETIME
);''');
}
/**
* crud functions
*/
void countPeople() async {
var db_connection = await db;
final count = Sqflite.firstIntValue(
await db_connection.rawQuery('SELECT COUNT(*) FROM persons'));
// assert(count == 2);
print('people count: $count');
}
Future<List<Person>> getAllPersons() async {
final db_connection = await db;
var response = await db_connection
.rawQuery("SELECT * FROM persons ORDER BY created DESC");
// print(response);
List<Person> list = response.map((c) => Person.fromJson(c)).toList();
return list;
}
// add new person
void addNewPerson(Person person) async {
var db_connection = await db;
String query = """
INSERT INTO persons(name,nickname,role,created,updated) VALUES('${person.name}','${person.nickname}', '${person.role}','${person.created}', '${person.updated}')
""";
await db_connection.transaction((transaction) async {
// print(query);
return await transaction.rawInsert(query);
});
}
下面是people_count.dart文件。这是我希望在 Text()
小部件中显示总记录数的地方。
import 'package:flutter/material.dart';
import 'package:com.example.simple_app/utils/db_helper.dart';
import 'package:com.example.simple_app/models/person.dart';
import 'package:com.example.simple_app/pages/main_user_registration/create_account.dart';
class MainUserRegistration extends StatefulWidget {
MainUserRegistration({Key key}) : super(key: key);
@override
_MainUserRegistrationState createState() => _MainUserRegistrationState();
}
var dbHelper = DBHelper();
class _MainUserRegistrationState extends State<MainUserRegistration> {
var result = dbHelper.countPeople();
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text('Loans'),
),
body: new Container(
child: Row(
children: <Widget>[
Text('all persons: ${dbHelper.countPeople()}'), // the total number of records should appear here
],
),
),
);
}
}
您可能应该尝试使用 setState()
来更改 initState
上的异步数据,这是 people_count.dart
的样子:
import 'package:flutter/material.dart';
import 'package:com.example.simple_app/utils/db_helper.dart';
import 'package:com.example.simple_app/models/person.dart';
import 'package:com.example.simple_app/pages/main_user_registration/create_account.dart';
class MainUserRegistration extends StatefulWidget {
MainUserRegistration({Key key}) : super(key: key);
@override
_MainUserRegistrationState createState() => _MainUserRegistrationState();
}
var dbHelper = DBHelper();
class _MainUserRegistrationState extends State<MainUserRegistration> {
int number = -1;
void countPeople() async {
int count = await dbHelper.countPeople();
setState(() => number = count);
@override
void initState() {
super.initState();
countPeople();
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: Text('Money Lender'),
),
body: new Container(
child: Row(
children: <Widget>[
Text('all persons: ${number}'), // the total number of records should appear here
],
),
),
);
}
}
而db_helper.dart中的人数统计函数应该return人数:
Future<int>countPeople() async {
var db_connection = await db;
final count = Sqflite.firstIntValue(
await db_connection.rawQuery('SELECT COUNT(*) FROM persons'));
// assert(count == 2);
print('people count: $count');
return count;
}