[英]How to implement FutureBuilder dart, flutter
我有這個 static function 從我的數據庫(firebasefirestore)返回一個未來。 現在我需要它是一個 double,因為我必須為使用過的 Widget 提供一個 double。 我發現 FutureBuilder 是一個可行的 Class 用於這種場景,我只是不確定如何在我的代碼中正確實現它。 請參閱下面的代碼:
class SomellierChart extends StatefulWidget {
SomellierChart(
{Key? key,
required this.color,
required this.textColor,
required this.queryDocumentSnapshot})
: super(key: key);
Color textColor;
Color color;
List<QueryDocumentSnapshot> queryDocumentSnapshot;
@override
_SomellierChartState createState() => _SomellierChartState();
}
class _SomellierChartState extends State<SomellierChart> {
static Future<double> spotData(String day, queryDocumentSnapshot) async {
final documentSnapshot = await FirebaseFirestore.instance
.collection('users')
.doc(FirebaseAuth.instance.currentUser!.uid.toString())
.collection('activity')
.doc('${globals.year}')
.collection('week${globals.week}')
.doc(day.toString())
.get();
if (documentSnapshot.exists) {
print('Document exists');
return documentSnapshot['usage'].toDouble();
} else {
print('Document doesnt exist');
return 0;
}
}
@override
Widget build(BuildContext context) {
return LineChart(
LineChartData(
gridData: FlGridData(
show: false,
),
titlesData: FlTitlesData(
show: true,
rightTitles: SideTitles(showTitles: false),
topTitles: SideTitles(showTitles: false),
leftTitles: SideTitles(showTitles: false),
bottomTitles: SideTitles(
showTitles: true,
reservedSize: 20,
interval: 1,
getTextStyles: (context, value) => GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).indicatorColor,
fontWeight: FontWeight.w600,
fontSize: 12,
),
),
getTitles: (value) {
switch (value.toInt()) {
case 0:
return 'Mon';
case 2:
return 'Tue';
case 4:
return 'Wed';
case 6:
return 'Thu';
case 8:
return 'Fri';
case 10:
return 'Sat';
case 12:
return 'Sun';
}
return '';
},
margin: 5,
),
),
borderData: FlBorderData(show: false),
minX: 0,
maxX: 12,
minY: 0,
maxY: 3,
lineBarsData: [
LineChartBarData(
spots: [
FlSpot(0, spotData('1', widget.queryDocumentSnapshot)),
FlSpot(2, spotData('2', widget.queryDocumentSnapshot)),
FlSpot(4, spotData('3', widget.queryDocumentSnapshot)),
FlSpot(6, spotData('4', widget.queryDocumentSnapshot)),
FlSpot(8, spotData('5', widget.queryDocumentSnapshot)),
FlSpot(10, spotData('6', widget.queryDocumentSnapshot)),
FlSpot(12, spotData('7', widget.queryDocumentSnapshot)),
],
isCurved: true,
curveSmoothness: 0.5,
preventCurveOverShooting: true,
colors: [widget.textColor],
barWidth: 3,
isStrokeCapRound: true,
dotData: FlDotData(
show: false,
),
belowBarData: BarAreaData(
show: true,
colors: [
widget.color.withOpacity(0.4),
],
),
),
],
),
);
}
}
double 需要提供給 FlSpot。 我使用 static function spotData(day, queryDocumentSnapshot) 這樣做 - 唯一的問題是:我返回的是 Future 而不是雙...
非常感謝你的幫助!
您可以執行以下操作:
initState()
中初始化futureDouble
snapshot.data!
(在這種情況下是double
,因為定義了FutureBuilder<double>
,但您可以為任何對象定義它)。class _SomellierChartState extends State<SomellierChart> {
late Future<double> futureDouble;
Future<double> spotData(String day, queryDocumentSnapshot) async {
...
}
@override
void initState() {
super.initState();
futureDouble = spotData('', null);
}
@override
Widget build(BuildContext context) {
return FutureBuilder<double>(
future: futureDouble,
builder: (context, snapshot) {
if (snapshot.hasData) {
return _lineChart(snapshot.data!);
} else if (snapshot.hasError) {
return Text('${snapshot.error}');
}
return const CircularProgressIndicator();
});
}
Widget _lineChart(double value) {
return LineChart(...
);
}
}
你也可以有一個雙列表,例如
late Future<List<double>> futureDouble;
Future<List<double>> spotData(String day, queryDocumentSnapshot) async {
...
}
和
return FutureBuilder<List<double>>(...)
其中snapshot.data!
將是List<double>
。
要有一個返回值列表的方法,你可以有類似的東西:
Future<List<double>> values() async {
var list = <double>[];
list.add(await value());
list.add(await value());
list.add(await value());
list.add(await value());
list.add(await value());
list.add(await value());
return list;
}
Future<double> value() async {
return 1;
}
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