【发布时间】：2021-08-28 14:48:30
【问题描述】：
我有一个 SingleChildScrollView，它的 Column 小部件有很多孩子。我想在“下一个屏幕上”保留一组按钮（例如“PageBreak 小部件”）。
我已经尝试过了，但它会产生异常，因为您只应该使用带有 Stack Widget（而不是 Column Widget）的 Positioned 小部件：
if (btnset is Spacer)
Positioned(
top: height,
child: SizedBox(
key: GlobalKey(
debugLabel: "NEXTSCREEN",
),
height: height / 2))
height/2太大了……旋转屏幕时效果不对……
完整的 UI 部分（查找“NEXTSCREEN”）：
return Scaffold(
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
floatingActionButton: Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
children: [
SizedBox(height: 80),
if (_scrollController.hasClients && _scrollController.offset > 0)
FloatingActionButton(
backgroundColor: Colors.white,
foregroundColor: Colors.blue,
child: Icon(Icons.arrow_upward),
mini: true,
heroTag: null,
onPressed: () {
if (_scrollController.hasClients)
_scrollController.animateTo(
_scrollController.offset -
_scrollController.position.viewportDimension,
duration: Duration(milliseconds: 500),
curve: Curves.ease);
}),
Spacer(),
if (_scrollController.hasClients &&
_scrollController.offset <
_scrollController.position.maxScrollExtent)
FloatingActionButton(
backgroundColor: Colors.white,
foregroundColor: Colors.blue,
mini: true,
heroTag: null,
child: Icon(Icons.arrow_downward),
onPressed: () {
if (_scrollController.hasClients)
_scrollController.animateTo(
_scrollController.offset +
_scrollController.position.viewportDimension,
duration: Duration(milliseconds: 500),
curve: Curves.ease);
}),
]),
appBar: AppBar(
title: Text(meshTag +
data['Name']
.strval() /*+
" " +
StatusWord(data['Alarms'].val).toString()*/
),
actions: [
StatusWordWidget(
data['Alarms'].val,
short: true,
direction: Axis.horizontal,
),
]),
//drawer: Drawer(), //You do this, the back arrow goes away...
body: !initialized
? Center(
child:
CircularProgressIndicator()) //Circle of Death while we connect
: Scrollbar(
thickness: 8.0,
isAlwaysShown: true,
child: SingleChildScrollView(
controller: _scrollController,
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
verticalDirection: VerticalDirection.down,
children: <Widget>[
Container(
margin: EdgeInsets.fromLTRB(
0, 0, 10, 2), //Make room for scroll bar!
child: headerRow()),
Row(
mainAxisAlignment: MainAxisAlignment.center,
mainAxisSize: MainAxisSize.min,
children: <Widget>[
RotatedBox(
quarterTurns: -1,
child: ConstrainedBox(
constraints: BoxConstraints.tightFor(
height: 50, width: chartHeight),
child: Center(
child: SliderTheme(
data: SliderThemeData(
trackShape: CustomTrackShape()),
child: Slider(
value: localset * 1.0,
max: maxy,
min: miny,
onChanged: (double value) {
setState(() {
localset = value.toInt();
});
}))))),
Expanded(child: chartwidget)
]),
if (localset != data['Setpoint'].val)
ElevatedButton(
child: Text('Set Setpoint to: ' + localset.toString()),
onPressed: (localset == data['Setpoint'].val)
? null
: () {
//Write Value to Ble.
setState(() {
data['Setpoint'].val = localset;
data['Setpoint'].bttx();
});
},
),
Divider(),
for (var btnset in mainButtons) ...[
if (btnset is Spacer)
SizedBox(
key: GlobalKey(
debugLabel: "NEXTSCREEN",
),
height: height / 3)
else ...[btnset, Divider()]
],
Divider(),
GestureDetector(
child: Divider(
thickness: 8,
),
onLongPress: () {
showdev = true;
},
),
if (showdev) ...{
ElevatedButton(
onPressed: () {
//Load the log
loadlogtext();
},
child: Text("Read")),
ConstrainedBox(
constraints: BoxConstraints(minWidth: 300),
child: Text(logtext)),
Divider(),
//ToDo: A debug datatable with all vars.
DataTable(
showCheckboxColumn: false,
columns: [
DataColumn(
label: Text("Name"),
numeric: false,
tooltip: "Name of parameter",
),
DataColumn(
label: Expanded(child: Text("Value")),
numeric: true,
tooltip: "Signal Strength",
),
],
rows: DeviceData.entries
.map(
(item) => DataRow(
onSelectChanged: (bool? selected) {
print('Picked ${item.name}');
},
cells: [
DataCell(Container(
//width: 120,
child: Text(item.name),
)),
DataCell(
Container(
width: 40,
child: Text((item.isnum
? item.val.toString()
: item.str == null
? "<null>"
: item.str)!)),
),
]),
)
.toList(),
),
Divider()
},
Row(
mainAxisAlignment: MainAxisAlignment.center,
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Padding(
padding: EdgeInsets.all(20.0),
child: OutlinedButton(
child: Text('Back'),
onPressed: () {
Navigator.pop(context);
},
),
),
],
),
ConstrainedBox(
constraints: BoxConstraints(
minHeight: 40)) //Keep the button off the bottom...
],
),
)),
);
}
}
【问题讨论】：
-
分享完整代码
-
完成...似乎不太清楚。
标签： flutter