無法弄清楚如何在 flutter 中使用 SharedPreferences，請幫助:)
[英]Can't figure it out how to use SharedPreferences in flutter, please help :)
問題描述
我試圖在我的應用程序中制作一個星星計數器，當應用程序關閉並重新打開時，星星的數量應該保持不變，而不是再次從 0 開始。 我所做的就是這個，但它不起作用。
int correctGuesses = 0;
String language1 = "";
String language2 = "";
String language3 = "";
Widget buildGame() {
final myController = TextEditingController();
@override
void dispose() {
myController.dispose();
super.dispose();
}
int nextNumber({required int min, required int max}) =>
min + Random().nextInt(max - min + 1);
int rowNumber = Random().nextInt(1);
int columnNumber = nextNumber(min: 1, max: 10);
final language = languageMatrix[rowNumber][0];
final sentence = languageMatrix[rowNumber][columnNumber];
return SingleChildScrollView(
child: Column(
children: <Widget> [
Image.asset('assets/GameLogo_2.png'),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 0),
child: Container(
decoration: BoxDecoration(
color: Colors.teal[200],
borderRadius: const BorderRadius.all(Radius.circular(10)),
border: Border.all(color: Colors.black)
),
height: 125,
child: Center(
child: Text(
sentence,
style: const TextStyle(fontSize: 17),
textAlign: TextAlign.center,
)
),
),
),
Container(height: 20),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget> [
Padding(
padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 10),
child: SizedBox(
width: 200,
//height: 70,
child: TextField(
cursorColor: Colors.teal,
controller: myController,
decoration: const InputDecoration(
border: OutlineInputBorder(),
hintText: 'Enter a language',
),
),
)
),
TextButton(
style: TextButton.styleFrom(
textStyle: const TextStyle(fontSize: 20)),
onPressed: () {
_incrementCounter();
if (counter >= 1 && counter <= 3 )
{
if (myController.text == language)
{
if (counter == 1)
{
language1 = language;
firstAttempt = myController.text;
correctGuesses++;
}
if (counter == 2)
{
language2 = language;
secondAttempt = myController.text;
correctGuesses++;
}
if (counter == 3)
{
language3 = language;
thirdAttempt = myController.text;
correctGuesses++;
}
}
else
{
if (counter == 1)
{
language1 = language;
firstAttempt = myController.text;
}
if (counter == 2)
{
language2 = language;
secondAttempt = myController.text;
}
if (counter == 3)
{
language3 = language;
thirdAttempt = myController.text;
}
}
}
if (counter == 3)
{
if (correctGuesses == 0)
{
showDialog<String>(
barrierDismissible: false,
context: context,
builder: (BuildContext context) => AlertDialog(
title: const Text('Your Score', textAlign: TextAlign.center, style: TextStyle(fontSize: 25),),
content: SizedBox(
height: 250,
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
Icon(Icons.star_border, size: 70, color: Colors.teal),
Icon(Icons.star_border, size: 70, color: Colors.teal),
Icon(Icons.star_border, size: 70, color: Colors.teal),
],
),
Container(height: 15),
Text('Sentence 1: $language1', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 2: $language2', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 3: $language3', textAlign: TextAlign.center),
Container(height: 15),
const Text('Check your profile to see your total number of stars, or go back home and start a new round!', textAlign: TextAlign.center,)
]
)
),
elevation: 24,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
actionsAlignment: MainAxisAlignment.spaceAround,
actions: <Widget>[
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => StartPage())),
child: const Text('Home'),
),
TextButton(
onPressed: () {
Navigator.push(context, MaterialPageRoute(builder: (context) => ProfilePage()));
},
child: const Text('Profile'),
),
],
)
);
}
if (correctGuesses == 1)
{
showDialog<String>(
barrierDismissible: false,
context: context,
builder: (BuildContext context) => AlertDialog(
title: const Text('Your Score', textAlign: TextAlign.center, style: TextStyle(fontSize: 25),),
content: SizedBox(
height: 250,
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
Icon(Icons.star, size: 70, color: Colors.teal),
Icon(Icons.star_border, size: 70, color: Colors.teal),
Icon(Icons.star_border, size: 70, color: Colors.teal),
],
),
Container(height: 15),
Text('Sentence 1: $language1', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 2: $language2', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 3: $language3', textAlign: TextAlign.center),
Container(height: 15),
const Text('Check your profile to see your total number of stars, or go back home and start a new round!', textAlign: TextAlign.center,)
]
)
),
elevation: 24,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
actionsAlignment: MainAxisAlignment.spaceAround,
actions: <Widget>[
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => StartPage())),
child: const Text('Home'),
),
TextButton(
onPressed: () {
//setStarsNumber(correctGuesses);
Navigator.push(context, MaterialPageRoute(builder: (context) => ProfilePage()));
},
child: const Text('Profile'),
),
],
)
);
}
if (correctGuesses == 2)
{
showDialog<String>(
barrierDismissible: false,
context: context,
builder: (BuildContext context) => AlertDialog(
title: const Text('Your Score', textAlign: TextAlign.center, style: TextStyle(fontSize: 25),),
content: SizedBox(
height: 250,
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
Icon(Icons.star, size: 70, color: Colors.teal),
Icon(Icons.star, size: 70, color: Colors.teal),
Icon(Icons.star_border, size: 70, color: Colors.teal),
],
),
Container(height: 15),
Text('Sentence 1: $language1', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 2: $language2', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 3: $language3', textAlign: TextAlign.center),
Container(height: 15),
const Text('Check your profile to see your total number of stars, or go back home and start a new round!', textAlign: TextAlign.center,)
]
)
),
elevation: 24,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
actionsAlignment: MainAxisAlignment.spaceAround,
actions: <Widget>[
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => StartPage())),
child: const Text('Home'),
),
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => ProfilePage())),
child: const Text('Profile'),
),
],
)
);
}
if (correctGuesses == 3)
{
showDialog<String>(
barrierDismissible: false,
context: context,
builder: (BuildContext context) => AlertDialog(
title: const Text('Your Score', textAlign: TextAlign.center, style: TextStyle(fontSize: 25),),
content: SizedBox(
height: 250,
child: Column(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
Icon(Icons.star, size: 70, color: Colors.teal),
Icon(Icons.star, size: 70, color: Colors.teal),
Icon(Icons.star, size: 70, color: Colors.teal),
],
),
Container(height: 15),
Text('Sentence 1: $language1', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 2: $language2', textAlign: TextAlign.center),
Container(height: 15),
Text('Sentence 3: $language3', textAlign: TextAlign.center),
Container(height: 15),
const Text('Check your profile to see your total number of stars, or go back home and start a new round!', textAlign: TextAlign.center,)
]
)
),
elevation: 24,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
actionsAlignment: MainAxisAlignment.spaceAround,
actions: <Widget>[
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => StartPage())),
child: const Text('Home'),
),
TextButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (context) => ProfilePage())),
child: const Text('Profile'),
),
],
)
);
}
}
myController.clear();
},
child: const Text('Guess'),
)
]
),
Container(height: 20),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 100, vertical: 5),
child: Container(
height: 30,
decoration: BoxDecoration(
color: Colors.teal[200],
borderRadius: const BorderRadius.all(Radius.circular(10)),
border: Border.all(color: Colors.black),
),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget> [
const Text('Sentence 1/3: '),
Text(firstAttempt)
]
)
)
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 100, vertical: 5),
child: Container(
height: 30,
decoration: BoxDecoration(
color: Colors.teal[200],
borderRadius: const BorderRadius.all(Radius.circular(10)),
border: Border.all(color: Colors.black),
),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget> [
const Text('Sentence 2/3: '),
Text(secondAttempt)
]
)
)
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 100, vertical: 5),
child: Container(
height: 30,
decoration: BoxDecoration(
color: Colors.teal[200],
borderRadius: const BorderRadius.all(Radius.circular(10)),
border: Border.all(color: Colors.black),
),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget> [
const Text('Sentence 3/3: '),
Text(thirdAttempt)
]
)
)
),
Container(
height: 10,
),
]
),
);
}
Future<int> getOldStarsNumber() async {
final SharedPreferences pref = await SharedPreferences.getInstance();
int oldStarsNumber = (pref.getInt('keyStarsNumber') ?? 0);
return oldStarsNumber;
}
Future<void> updateStarsNumber() async{
final SharedPreferences pref = await SharedPreferences.getInstance();
int oldStarsNumber = await getOldStarsNumber();
int starsNumber = correctGuesses + oldStarsNumber;
pref.setInt('keyStarsNumber', 0);
}
這是我使用的第一個 class 的數據，這是我計算星數的地方。
class ProfilePageState extends State<ProfilePage> {
int? starsNumber;
@override
void initState() {
super.initState();
setStarsNumber();
}
Future<void> setStarsNumber() async {
final SharedPreferences pref = await SharedPreferences.getInstance();
starsNumber = pref.getInt('keyStarsNumber');
setState(() {
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('My profile, coming soon'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Icon(Icons.star, size: 200, color: Colors.teal,),
Text('$starsNumber', style: const TextStyle(fontSize: 100)),
],
),
),
);
}
}
這是第二個 class，我在其中獲得了該數量的星星並將其放入文本中。 有了這段代碼，星星總數始終保持為0，我不知道該怎么辦，所以請幫忙。 correctGuesses 變量來自上面的小部件 Build，它確實有效……我所想的是，這可能是 correctGuesses 變量失去了它的價值。 我認為我 100% 錯了..但這就是我的想法。 請幫助我，我卡住了：）非常感謝！
1 個解決方案
解決方案1
0 已采納 2022-09-01 09:45:32
我認為您的代碼的問題在於，您在 updateStarsNumber function 中的每次更新時一遍又一遍地初始化共享首選項的實例。 嘗試擁有一個應用程序范圍內的共享首選項實例。 您可以在主 function 中對其進行初始化，將其命名為 prefs，並在需要的地方注入它。
基本上，只調用 await SharedPreferences.getInstance(); 一次在應用程序中。
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