[英]Add Scrolling in the ListView.builder in Flutter application
I am trying to make a List view scroll able, when I googled and could not found an understandable and simple solution, I tried to make a custom scroll (example from link https://docs.flutter.io/flutter/widgets/ListView-class.html ), at the moment it is not working. 我试图使列表视图滚动成为可能,当我用Google搜索并且找不到可理解和简单的解决方案时,我试图进行自定义滚动(例如,来自链接https://docs.flutter.io/flutter/widgets/ListView的示例-class.html ),目前无法正常工作。
Here is the code: 这是代码:
CustomScrollView(
shrinkWrap: true,
slivers: <Widget>[
SliverPadding(
padding: const EdgeInsets.all(20.0),
sliver: SliverList(
delegate: SliverChildListDelegate(
<Widget>[
StreamBuilder(
stream: Firestore.instance.collection("Items").snapshots(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
return new ListView.builder(
padding: const EdgeInsets.only(top: 5.0),
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: snapshot.data.documents.length,
itemBuilder: (BuildContext context,int index) {
DocumentSnapshot ds = snapshot.data.documents[index];
return new Row(
textDirection: TextDirection.ltr,
children: <Widget>[
Expanded(child: Text(ds["item1"])),
Expanded(child: Text(ds["item2"])),
Expanded(child: Text(ds["price"].toString())),
],
);
});
}
else {
return Align(
alignment: FractionalOffset.bottomCenter,
child: CircularProgressIndicator(),
);
}
},
)
],
),
),
),
],
)
Below is the screenshot from emulator (Kindly node, same on the phone): 下面是模拟器的截图(亲切的节点,在手机上相同):
Kindly help me with pointers or sample code for scroll-able list view. 请帮助我提供可滚动列表视图的指针或示例代码。
You don't need to use a CustomScrollView. 您不需要使用CustomScrollView。 ListView is a scrolling widget itself. ListView是一个滚动小部件本身。 So you only need to create it inside your StreamBuilder. 因此,您只需要在StreamBuilder中创建它。
@override
Widget build(BuildContext context) {
return StreamBuilder<List<int>>(
stream: posts,
builder: (BuildContext context, AsyncSnapshot<List<int>> snapshot) {
if (snapshot.hasError) {
return Text('Error: ${snapshot.error}');
}
switch (snapshot.connectionState) {
case ConnectionState.waiting:
return const Text('Loading...');
default:
if (snapshot.data.isEmpty) {
return const NoContent();
}
return _itemList(snapshot.data);
}
},
);
}
CustomScrollView is used for adding Sliver widget inside it. CustomScrollView用于在其中添加Sliver小部件。
You are wrapping a ListView
inside a SliverList
, which is never a good idea if they have the same scrolling direction. 您将ListView
包裹在SliverList
,如果它们具有相同的滚动方向,则永远不是一个好主意。 You could either do a Column
with a List.generate()
generator (inefficient) or get rid of one of the ListView
's: 您可以使用List.generate()
生成器(效率低下)来做一Column
,也可以摆脱ListView
的其中之一:
CustomScrollView(
shrinkWrap: true,
slivers: <Widget>[
StreamBuilder(
stream: Firestore.instance.collection("Items").snapshots(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
return SliverPadding(
padding: const EdgeInsets.all(20.0),
sliver: SliverList(
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
DocumentSnapshot ds = snapshot.data.documents[index];
return new Row(
textDirection: TextDirection.ltr,
children: <Widget>[
Expanded(child: Text(ds["item1"])),
Expanded(child: Text(ds["item2"])),
Expanded(child: Text(ds["price"].toString())),
],
);
},
childCount: snapshot.data.documents.length,
),
),
);
} else {
return SliverFillRemaining(
child: Center(
child: CircularProgressIndicator(),
),
);
}
},
),
],
);
If this code snippet doesn't work swap the StreamBuilder
with the CustomScrollView
如果此代码段不起作用, StreamBuilder
与CustomScrollView
交换
ListView
itself is a scroll able list so you just create it with your custom tiles. ListView
本身是可滚动的列表,因此您只需使用自定义图块即可创建它。 Here is the code from my to-do list app that I used to create a list of my to-do items. 这是我的待办事项列表应用程序中的代码,用于创建待办事项列表。 Well I call this function when I have to create a list. 好了,当我必须创建一个列表时,我就调用此函数。
/*Called each time the widget is built.
* This function creates the list with all items in '_todoList'
* */
Widget _buildTodoList() {
return new ListView.builder(
// itemBuilder will be automatically be called as many times as it takes for the
// list to fill up its available space, which is most likely more than the
// number of to do items we have. So, we need to check the index is OK.
itemBuilder: (context, index) {
if (index < _todoList.length) {
return _buildTodoItem(_todoList[index],index);
}
},
);
}
Now this function calls a _buildTodoItem
function which creates a single custom list tile. 现在,此函数调用_buildTodoItem
函数,该函数创建一个自定义列表_buildTodoItem
贴。
/*Build a single List Tile*/
Widget _buildTodoItem(TodoItem todoItem,int index) {
//return a custom build single tile for your list
}
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