位于中心的颤振位置叠加小部件

小开

最佳答案

除了这个:

Align(
alignment: Alignment.bottomCenter,
child: new ButtonBar(
alignment: MainAxisAlignment.center,
children: <Widget>[
new OutlineButton(
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(
builder: (context) => new LoginPage()));
},
child: new Text(
"Login",
style: new TextStyle(color: Colors.white),
),
),
new RaisedButton(
color: Colors.white,
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(
builder: (context) =>
new RegistrationPage()));
},
child: new Text(
"Register",
style: new TextStyle(color: Colors.black),
),
)
],
),
)

在我的理论中，额外的 Container正在摧毁它。我建议你只是围绕这个加上 Padding:

Padding(
padding: EdgeInsets.only(bottom: 20.0),
child: Align...
),

这对我来说似乎比 Positioned更合理，而且我也不完全理解你的 Column只有一个孩子。

小开

问题是容器的大小尽可能的小。

只要给容器一个 width:(红色) ，你就完成了。

width: MediaQuery.of(context).size.width

  new Positioned(
bottom: 0.0,
child: new Container(
width: MediaQuery.of(context).size.width,
color: Colors.red,
margin: const EdgeInsets.all(0.0),
child: new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Align(
alignment: Alignment.bottomCenter,
child: new ButtonBar(
alignment: MainAxisAlignment.center,
children: <Widget>[
new OutlineButton(
onPressed: null,
child: new Text(
"Login",
style: new TextStyle(color: Colors.white),
),
),
new RaisedButton(
color: Colors.white,
onPressed: null,
child: new Text(
"Register",
style: new TextStyle(color: Colors.black),
),
)
],
),
)
],
),
),
),

小开

您可以更改堆栈中的“对齐位置”:

Align(
alignment: Alignment.bottomCenter,
child: ... ,
),

了解更多关于堆栈的信息: 探索堆栈

小开

你可以在 Stack中使用 Positioned.fill和 Align:

Stack(
children: <Widget>[
Positioned.fill(
child: Align(
alignment: Alignment.centerRight,
child: ....
),
),
],
),

小开

对于那些到达这里却无法解决问题的人，我过去常常把我的窗口小部件设置为水平居中，像下面这样左右都设置为0:

Stack(
children: <Widget>[
Positioned(
top: 100,
left: 0,
right: 0,
child: Text("Search",
style: TextStyle(
color: Color(0xff757575),
fontWeight: FontWeight.w700,
fontFamily: "Roboto",
fontStyle: FontStyle.normal,
fontSize: 56.0,
),
textAlign: TextAlign.center,
),
),
]
)

小开

也许是最优雅的方式。

您可以简单地使用 Stack中的 alignment选项

child: Stack(
alignment: Alignment.center
)

小开

你也可以试试这个:

Center(
child: Stack(
children: [],
),
)

小开

感谢以上所有的回答，我想分享一些在某些情况下可能会派上用场的东西。因此，让我们看看使用 Positioned:( right: 0.0, left:0.0, bottom:0.0)时会发生什么:

      Padding(
padding: const EdgeInsets.all(4.0),
child: Stack(
children: <Widget>[
Positioned(
bottom: 0.0,
right: 0.0,
left: 0.0,
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 8.0),
child: Container(
color: Colors.blue,
child: Center(
child: Text('Hello',
style: TextStyle(color: Color(0xffF6C37F),
fontSize: 46, fontWeight: FontWeight.bold),),
)
),
)
),
],
),
),

这将是上述代码的输出:

正如您所看到的，它将用容器填充整个宽度，即使您不想要它，并且您只希望容器包装它的子容器。因此，你可以尝试下面的技巧:

      Padding(
padding: const EdgeInsets.all(4.0),
child: Stack(
children: <Widget>[
Positioned(
bottom: 0.0,
right: 0.0,
left: 0.0,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 8.0),
child: Container(
color: Colors.blue,
child: Text('Hello',
style: TextStyle(color: Color(0xffF6C37F),
fontSize: 46, fontWeight: FontWeight.bold),)
),
),
Container(),
],
)
),
],
),
),

小开

看看我想到的这个解决方案

Positioned( child: SizedBox( child: CircularProgressIndicator(), width: 50, height: 50,), left: MediaQuery.of(context).size.width / 2 - 25);

小开

对我来说，最好的办法就是使用 Align。我需要使用户的个人资料图片在封面图片的底部中心。

return Container(
height: 220,
color: Colors.red,
child: Stack(
children: [
Container(
height: 160,
color: Colors.yellow,
),
Align(
alignment: Alignment.bottomCenter,
child: UserProfileImage(),
),
],
),
);

这招真管用。

小开

它可以像定位中心一样工作您可以确定小部件的中心，并设置小部件和点的相同中心。

import 'dart:developer';


import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'dart:math' as math;


class AlignPositioned extends SingleChildRenderObjectWidget {
const AlignPositioned({
Key? key,
this.alignment = Alignment.center,
required this.centerPoint,
this.widthFactor,
this.heightFactor,
Widget? child,
})  : assert(widthFactor == null || widthFactor >= 0.0),
assert(heightFactor == null || heightFactor >= 0.0),
super(key: key, child: child);


final AlignmentGeometry alignment;
final Offset centerPoint;


final double? widthFactor;


final double? heightFactor;


@override
_RenderPositionedBox createRenderObject(BuildContext context) {
return _RenderPositionedBox(
alignment: alignment,
widthFactor: widthFactor,
heightFactor: heightFactor,
textDirection: Directionality.maybeOf(context),
centerPoint: this.centerPoint,
);
}


@override
void updateRenderObject(
BuildContext context, _RenderPositionedBox renderObject) {
renderObject
..alignment = alignment
..widthFactor = widthFactor
..heightFactor = heightFactor
..textDirection = Directionality.maybeOf(context)
..centerPoint = centerPoint;
}


@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties
.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment));
properties
.add(DoubleProperty('widthFactor', widthFactor, defaultValue: null));
properties
.add(DoubleProperty('heightFactor', heightFactor, defaultValue: null));
}
}


class _RenderPositionedBox extends RenderAligningShiftedBox {
Offset centerPoint;


_RenderPositionedBox({
RenderBox? child,
double? widthFactor,
double? heightFactor,
AlignmentGeometry alignment = Alignment.center,
TextDirection? textDirection,
required this.centerPoint,
})  : assert(widthFactor == null || widthFactor >= 0.0),
assert(heightFactor == null || heightFactor >= 0.0),
_widthFactor = widthFactor,
_heightFactor = heightFactor,
super(child: child, alignment: alignment, textDirection: textDirection);


double? get widthFactor => _widthFactor;
double? _widthFactor;


set widthFactor(double? value) {
assert(value == null || value >= 0.0);
if (_widthFactor == value) return;
_widthFactor = value;
markNeedsLayout();
}


set alignment(AlignmentGeometry value) {
super.alignment = value;
_resolvedAlignment = alignment.resolve(textDirection);
}


double? get heightFactor => _heightFactor;
double? _heightFactor;
late Alignment _resolvedAlignment = alignment.resolve(textDirection);


set heightFactor(double? value) {
assert(value == null || value >= 0.0);
if (_heightFactor == value) return;
_heightFactor = value;
markNeedsLayout();
}


@override
Size computeDryLayout(BoxConstraints constraints) {
final bool shrinkWrapWidth =
_widthFactor != null || constraints.maxWidth == double.infinity;
final bool shrinkWrapHeight =
_heightFactor != null || constraints.maxHeight == double.infinity;
if (child != null) {
final Size childSize = child!.getDryLayout(constraints.loosen());
return constraints.constrain(Size(
shrinkWrapWidth
? childSize.width * (_widthFactor ?? 1.0)
: double.infinity,
shrinkWrapHeight
? childSize.height * (_heightFactor ?? 1.0)
: double.infinity,
));
}
return constraints.constrain(Size(
shrinkWrapWidth ? 0.0 : double.infinity,
shrinkWrapHeight ? 0.0 : double.infinity,
));
}


@override
void performLayout() {
final BoxConstraints constraints = this.constraints;
final bool shrinkWrapWidth =
_widthFactor != null || constraints.maxWidth == double.infinity;
final bool shrinkWrapHeight =
_heightFactor != null || constraints.maxHeight == double.infinity;


if (child != null) {
child!.layout(constraints.loosen(), parentUsesSize: true);
size = constraints.constrain(Size(
shrinkWrapWidth
? child!.size.width * (_widthFactor ?? 1.0)
: double.infinity,
shrinkWrapHeight
? child!.size.height * (_heightFactor ?? 1.0)
: double.infinity,
));


final BoxParentData childParentData = child!.parentData! as BoxParentData;
final moveX = _resolvedAlignment.x - 1;
final moveY = _resolvedAlignment.y - 1;
log(_resolvedAlignment.y.toString());
childParentData.offset = this.centerPoint +
Offset(
child!.size.width / 2 * moveX,
child!.size.height / 2 * moveY,
);
// log(_resolvedAlignment.x.toString());
// log(_resolvedAlignment.y.toString());


// _resolvedAlignment.alongOffset(size - child!.size as Offset);
} else {
size = constraints.constrain(Size(
shrinkWrapWidth ? 0.0 : double.infinity,
shrinkWrapHeight ? 0.0 : double.infinity,
));
}
}


@override
void debugPaintSize(PaintingContext context, Offset offset) {
super.debugPaintSize(context, offset);
assert(() {
final Paint paint;
if (child != null && !child!.size.isEmpty) {
final Path path;
paint = Paint()
..style = PaintingStyle.stroke
..strokeWidth = 1.0
..color = const Color(0xFFFFFF00);
path = Path();
final BoxParentData childParentData =
child!.parentData! as BoxParentData;
if (childParentData.offset.dy > 0.0) {
// vertical alignment arrows
final double headSize =
math.min(childParentData.offset.dy * 0.2, 10.0);
path
..moveTo(offset.dx + size.width / 2.0, offset.dy)
..relativeLineTo(0.0, childParentData.offset.dy - headSize)
..relativeLineTo(headSize, 0.0)
..relativeLineTo(-headSize, headSize)
..relativeLineTo(-headSize, -headSize)
..relativeLineTo(headSize, 0.0)
..moveTo(offset.dx + size.width / 2.0, offset.dy + size.height)
..relativeLineTo(0.0, -childParentData.offset.dy + headSize)
..relativeLineTo(headSize, 0.0)
..relativeLineTo(-headSize, -headSize)
..relativeLineTo(-headSize, headSize)
..relativeLineTo(headSize, 0.0);
context.canvas.drawPath(path, paint);
}
if (childParentData.offset.dx > 0.0) {
// horizontal alignment arrows
final double headSize =
math.min(childParentData.offset.dx * 0.2, 10.0);
path
..moveTo(offset.dx, offset.dy + size.height / 2.0)
..relativeLineTo(childParentData.offset.dx - headSize, 0.0)
..relativeLineTo(0.0, headSize)
..relativeLineTo(headSize, -headSize)
..relativeLineTo(-headSize, -headSize)
..relativeLineTo(0.0, headSize)
..moveTo(offset.dx + size.width, offset.dy + size.height / 2.0)
..relativeLineTo(-childParentData.offset.dx + headSize, 0.0)
..relativeLineTo(0.0, headSize)
..relativeLineTo(-headSize, -headSize)
..relativeLineTo(headSize, -headSize)
..relativeLineTo(0.0, headSize);
context.canvas.drawPath(path, paint);
}
} else {
paint = Paint()..color = const Color(0x90909090);
context.canvas.drawRect(offset & size, paint);
}
return true;
}());
}


@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties
.add(DoubleProperty('widthFactor', _widthFactor, ifNull: 'expand'));
properties
.add(DoubleProperty('heightFactor', _heightFactor, ifNull: 'expand'));
}
}