问题描述
我的练习以字符串形式存储在我的sqflite数据库中。我想检索数据并将其放入名为 typeArray [] 的列表或数组中。我正在尝试在一个类中检索数据，该类将使用函数中的练习列表来执行随机锻炼生成。因此，在进行计算之前，我需要检索列表。然后，使用MaterialPageRoute（）将这些锻炼生成器函数的返回值传递给 custom_workout_screen.dart ，在这里我使用函数的返回值以字符串形式显示在屏幕上。
我将其与预定义列表一起使用，即在其中设置列表= ['exerciSEOne'，'exerciseTwo'，'etc']
如何在非无状态或全状态的类中提取数据？我很高兴从事这项工作，但在解决问题的方法上感到困惑-任何指导表示赞赏！
生成自定义锻炼并传递到“自定义锻炼”屏幕：generate_custom.dart
class GenerateCustom {
int rnd;
// NEED TO SET typeArray to values from SQFLITE DB ?
List typeArray = [];
GenerateCustom({this.difficulty});
final int difficulty;
String workout;
String ex1;
String ex2;
String ex3;
String ex4;
String ex5;
String getStrengthType() {
var random = Random();
var i = random.nextInt(14);
print(typeArray[i]);
return typeArray[i];
}
String cuExerciSEOne() {
if (difficulty == 1) {
workout = ('1: ' +
getStrengthType() +
' ' +
getRepsEasy() +
'x' +
getSetsEasy());
} else if (difficulty == 2) {
workout = ('1: ' +
getStrengthType() +
' ' +
getRepsMedium() +
'x' +
getSetsMedium());
} else {
workout = ('1: ' +
getStrengthType() +
' ' +
getRepsHard() +
'x' +
getSetsHard());
}
return workout;
}
DatabaseHelper： database_helper.dart
class DatabaseHelper {
static DatabaseHelper _databaseHelper;
static Database _database;
String exerciseTable = 'exercise_table';
String colId = 'id';
String title = 'title';
DatabaseHelper._createInstance();
factory DatabaseHelper() {
if (_databaseHelper == null) {
_databaseHelper = DatabaseHelper._createInstance();
}
return _databaseHelper;
}
Future<Database> get database async {
if (_database == null) {
_database = await initializeDatabase();
}
return _database;
}
Future<Database> initializeDatabase() async {
//get ios + android dir path
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'exercise.db';
//Open or create db at path
var exerciseDatabase =
await openDatabase(path,version: 1,onCreate: _createDb);
return exerciseDatabase;
}
void _createDb(Database db,int newVersion) async {
await db.execute(
'CREATE TABLE $exerciseTable ($colId INTEGER PRIMARY KEY,$title TEXT)');
}
Future<List<Map<String,dynamic>>> getExerciseMapList() async {
Database db = await this.database;
var result = await db.rawQuery('SELECT * FROM $exerciseTable');
return result;
}
//Insert
Future<int> insertExercise(Exercise exercise) async {
Database db = await this.database;
var result = await db.insert(exerciseTable,exercise.toMap());
return result;
}
//Update
Future<int> updateExercise(Exercise exercise) async {
var db = await this.database;
var result = await db.update(exerciseTable,exercise.toMap(),where: '$colId = ?',whereArgs: [exercise.id]);
debugPrint('update called');
return result;
}
//Delete
Future<int> deleteExercise(int id) async {
var db = await this.database;
int result =
await db.rawDelete('DELETE FROM $exerciseTable WHERE $colId = $id');
return result;
}
//get no of objects in db
Future<int> getCount() async {
Database db = await this.database;
List<Map<String,dynamic>> x =
await db.rawQuery('SELECT COUNT (*) from $exerciseTable');
int result = Sqflite.firstIntValue(x);
return result;
}
//get Map list from db,convert to Exercise List object
Future<List<Exercise>> getExerciseList() async {
//get map list and # of entries in db
var exerciseMapList = await getExerciseMapList();
int count = exerciseMapList.length;
List<Exercise> exerciseList = List<Exercise>();
//Loop to create exercise list from a map list
for (int i = 0; i < count; i++) {
exerciseList.add(Exercise.fromMapObject(exerciseMapList[i]));
}
return exerciseList;
}
}
使用输出的屏幕： custom_workout_screen.dart
class CustomWorkoutScreen extends StatelessWidget {
CustomWorkoutScreen(
this.customDifficulty,this.customWorkout1,this.customWorkout2,this.customWorkout3,this.customWorkout4,this.customWorkout5);
final String customDifficulty;
final String customWorkout1;
final String customWorkout2;
final String customWorkout3;
final String customWorkout4;
final String customWorkout5;
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: kBackgroundColour,appBar: AppBar(
backgroundColor: kButtonAndBarColour,title: Text('CUSTOM',style: kTitleStyle),),body: Center(
child: Column(
children: <Widget>[
SizedBox(height: 15.0),Expanded(
child: Text(
'WORKOUT',style: kTitleStyleDark,Container(
child: Text(
'DIFFICULTY: ' + customDifficulty,SizedBox(
height: 25.0,Container(
margin: EdgeInsets.only(bottom: 10.0),child: Column(
children: <Widget>[
Text('READY...GO!',style: kCommentTextStyle),Text(
customWorkout1,style: kMainTextStyledDark,Text('REST 30s!',Text(
customWorkout2,Text(
customWorkout3,Text(
customWorkout4,Text(
customWorkout5,Text('GOOD JOB,REST!',Text('OR GO AGAIN?',],SizedBox(
height: 50.0,BottomButton(
buttonTitle: 'NEW WORKOUT',onTap: () {
Navigator.pop(context);
},);
}
}
解决方法
基本上有两种方法可以解决您的问题[据我所知，可能还有更多]。第一种方法是使用Provider package。下面，我将详细说明该方法：
第一种方法
假设您已经拥有Article文件，则可以为您随机选择的锻炼定义一个类（类似这样，但不一定是这种方式）。为了简化和关注概念，我假设数据库具有以下字段：DatabaseHelper
difficulty TEXT PRIMARY KEY,workout1 TEXT,workout2 TEXT,workout3 TEXT,workout4 TEXT,workout5 TEXT然后，您需要创建import 'package:flutter/foundation.dart';
class RandomWorkout {
final String difficulty;
final String workout1;
final String workout2;
final String workout3;
final String workout4;
final String workout5;
RandomWorkout({
@required this.difficulty,@required this.workout1,@required this.workout2,@required this.workout3,@required this.workout4,@required this.workout5,});
}
文件以处理所有与提供程序相关的功能[添加，删除，获取，但请专注于获取和设置]：
workout_provider.dart在您的class WorkoutProvider with ChangeNotifier {
List<RandomWorkout> _workouts = [];
List<Task> get items {
return [..._tasks];
}
Future<void> fetchAndSetWorkouts() async {
final dataList =
await DBHelper.getExerciseMapList();
_workouts = dataList
.map(
(item) => RandomWorkout(
difficulty: item['difficulty'],workout1: item['workout1'],workout2: item['workout2'],workout3: item['workout3'],workout4: item['workout4'],workout5: item['workout5'],),)
.toList();
notifyListeners();
}
}
文件中，您需要将main.dart小部件包装为您选择的提供商小部件（MultiProvider / Provider）。
最后，在您计划填充数据的文件中，可以使用MaterialApp从数据库中以未来的FutureBuilder异步地获取数据，并使用Provider.of<TaskProvider>(context,listen: false).fetchAndSetWorkouts()的构建器来检索数据。来自Consumer的项目获取器。
这可能要掌握很多，所以我建议您访问Provider程序包的文档页面以及GitHub上的示例，有很多人可以比我更好地解释
第二种方法
这是一种更简单的方法，但灵活性和效率较低。您只需直接在需要数据的地方异步使用workout_provider.dart即可，如下所示：
DatabaseHelper