我需要使用Flutter在Firestore中使用嵌套数组更新文档。
因此,我需要将整个文档放入地图中,在“ sections”数组中对地图进行重新排序,然后将数据存储回文档中。
但是我不熟悉如何将快照(DocumentSnapshot)的数据获取到Map中。
下面的示例对我尝试实现的目标无效:
final Map<String, dynamic> doc = snapshot.data as Map<String, dynamic>;
“ snapshot.data”包含文档的值。该文档的结构如下所示:
{
name: "Course 1"
sections: [
{name: "Section 1"},
{name: "Section 2"}
]
}
sections数组中的Maps重新排序后,我需要将数据保存回文档中。
这里是完整功能。相关代码在“ onDragFinish”中。
// Build editable list with draggable list tiles and swipe to delete
List<Widget> buildListViewEdit() {
final course = db.collection("school").document("3kRHuyk20UggHwm4wrUI")
.collection("course").document("74UsE9x7Bsgnjz8zKozv").snapshots();
return [
StreamBuilder(
stream: course,
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text("Loading...");
return Expanded(
child: DragAndDropList(
snapshot.data["sections"].length,
itemBuilder: (context, index) {
return Card(
child: ListTile(
title: Text(snapshot.data["sections"][index]["name"]),
onTap: () {
print("hello");
}
)
);
},
onDragFinish: (before, after) {
print('on drag finish $before $after');
//final docString = snapshot.data.toString();
final Map <String, dynamic> doc = snapshot.data;
//final tempSections = List.castFrom(snapshot.data["sections"]).toList();
//Map data = tempSections[before];
//tempSections.removeAt(before);
//tempSections.insert(after,data);
//snapshot.data["sections"] = tempSections;
//db.collection("school").document("3kRHuyk20UggHwm4wrUI")
//.collection("course").document("74UsE9x7Bsgnjz8zKozv").updateData(snapshot.data);
//var line = snapshot.data["sections"][before];
//snapshot.data["sections"].removeAt(before);
//snapshot.data["sections"].insert(after,line);
/*
List<Map> sections = docCopy["sections"];
Map data = docCopy["sections"][before];
sections.removeAt(before);
sections.insert(after, data);
print(sections);
*/
},
canDrag: (index) {
print('can drag $index');
return index != 3;
},
canBeDraggedTo: (one, two) => true,
dragElevation: 8.0,
)
);
}
)
];
}
尝试将snapshot.data复制到另一个变量时出错:
flutter: ══╡ EXCEPTION CAUGHT BY GESTURE LIBRARY ╞═══════════════════════════════════════════════════════════
flutter: The following assertion was thrown while routing a pointer event:
flutter: type 'DocumentSnapshot' is not a subtype of type 'Map<String, dynamic>'
flutter:
flutter: Either the assertion indicates an error in the framework itself, or we should provide substantially
flutter: more information in this error message to help you determine and fix the underlying cause.
flutter: In either case, please report this assertion by filing a bug on GitHub:
flutter: https://github.com/flutter/flutter/issues/new?template=BUG.md
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 _SectionScreenState.buildListViewEdit.<anonymous closure>.<anonymous closure> (package:teach_mob/screens/section_screen.dart:150:45)
工作示例
感谢您的协助。这是一个对我有用的完整示例:
// Build editable list with draggable list tiles and swipe to delete
List<Widget> buildListViewEdit() {
final course = db.collection("school").document("3kRHuyk20UggHwm4wrUI")
.collection("course").document("74UsE9x7Bsgnjz8zKozv").snapshots();
return [
StreamBuilder(
stream: course,
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text("Loading...");
return Expanded(
child: DragAndDropList(
snapshot.data["sections"].length,
itemBuilder: (context, index) {
return Card(
child: ListTile(
title: Text(snapshot.data["sections"][index]["name"]),
onTap: () {
print("hello");
}
)
);
},
onDragFinish: (before, after) {
print('on drag finish $before $after');
// Convert AsyncSnapshot to DocumentSnapshot and then
// create a map that can be changed and updated.
final Map <String, dynamic> doc = snapshot.data.data;
// Convert fixed length list to dynamic list, because items in
// fixed length lists can't be added / removed.
final tempSections = List.castFrom(doc["sections"]).toList();
// Get the data of the list item to be dragged
// Remove the data from the current position
// Add the data to the new position of the list
Map data = tempSections[before];
tempSections.removeAt(before);
tempSections.insert(after,data);
// Overwrite sections with new list array
doc["sections"] = tempSections;
// Store the data back into the firestore document
db.collection("school")
.document("3kRHuyk20UggHwm4wrUI")
.collection("course")
.document("74UsE9x7Bsgnjz8zKozv")
.updateData(doc);
},
canDrag: (index) {
print('can drag $index');
return index != 3;
},
canBeDraggedTo: (one, two) => true,
dragElevation: 8.0,
)
);
}
)
];
}
答案 0 :(得分:2)
更新至2020年9月
要从快照文档中获取数据,您现在必须调用snapshot.data()
(cloud_firestore 0.14.0 or higher
)
答案 1 :(得分:2)
2021 年 5 月更新
请参阅迁移到 cloud_firestore 2.0.0 here。
//Replace this:
- StreamBuilder<DocumentSnapshot>(
//With this:
+ StreamBuilder<DocumentSnapshot<Map<String, dynamic>>>(
创建变量时必须定义类型:
Future<void> example(
- DocumentReference documentReference,
+ DocumentReference<Map<String, dynamic>> documentReference,
- CollectionReference collectionReference,
+ CollectionReference<Map<String, dynamic>> collectionReference,
- Query query,
+ Query<Map<String, dynamic>> query,
) {
答案 2 :(得分:1)
看起来好像是因为您有一个流生成器,所以快照是 AsyncSnapshot<dynamic>
,当您抓取其.data时,您会得到一个 dynamic ,它返回一个 DocumentSnapshot ,然后您需要在此对象上调用.data 以获得正确的 Map<String, dynamic> data
< / strong>。
builder: (context, snapshot) {
final DocumentSnapshot ds = snapshot.data;
final Map<String, dynamic> map = ds.data;
}
您还可以使用内置函数将其追加到数组,但是看起来您想进行一些疯狂的排序,所以一切都很好。
答案 3 :(得分:1)
根据我们的讨论快照,它不是DocumentSnapshot
,而是AsyncSnapshot
使用snapshot.data
要获取实际地图,您可以使用snapshot.data.data
答案 4 :(得分:1)
class ItemsList extends StatelessWidget {
@override
Widget build(BuildContext context) {
// get the course document using a stream
Stream<DocumentSnapshot> courseDocStream = Firestore.instance
.collection('Test')
.document('4b1Pzw9MEGVxtnAO8g4w')
.snapshots();
return StreamBuilder<DocumentSnapshot>(
stream: courseDocStream,
builder: (context, AsyncSnapshot<DocumentSnapshot> snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
// get course document
var courseDocument = snapshot.data.data;
// get sections from the document
var sections = courseDocument['sections'];
// build list using names from sections
return ListView.builder(
itemCount: sections != null ? sections.length : 0,
itemBuilder: (_, int index) {
print(sections[index]['name']);
return ListTile(title: Text(sections[index]['name']));
},
);
} else {
return Container();
}
});
}
}
答案 5 :(得分:1)
要从文档快照中获取地图,请使用snapshot.data.data