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align_compat_flex.dart
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align_compat_flex.dart
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import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'dart:math' as math;
/* author: changhai.qiu email: [email protected] */
class AlignCompatRow extends _Flex {
AlignCompatRow({
Key key,
MainAxisAlignment mainAxisAlignment = MainAxisAlignment.start,
MainAxisSize mainAxisSize = MainAxisSize.max,
CrossAxisAlignment crossAxisAlignment = CrossAxisAlignment.center,
TextDirection textDirection,
VerticalDirection verticalDirection = VerticalDirection.down,
TextBaseline textBaseline,
List<Widget> children = const <Widget>[],
}) : super(
children: children,
key: key,
direction: Axis.horizontal,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: mainAxisSize,
crossAxisAlignment: crossAxisAlignment,
textDirection: textDirection,
verticalDirection: verticalDirection,
textBaseline: textBaseline,
);
}
class AlignCompatColumn extends _Flex {
AlignCompatColumn({
Key key,
MainAxisAlignment mainAxisAlignment = MainAxisAlignment.start,
MainAxisSize mainAxisSize = MainAxisSize.max,
CrossAxisAlignment crossAxisAlignment = CrossAxisAlignment.center,
TextDirection textDirection,
VerticalDirection verticalDirection = VerticalDirection.down,
TextBaseline textBaseline,
List<Widget> children = const <Widget>[],
}) : super(
children: children,
key: key,
direction: Axis.vertical,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: mainAxisSize,
crossAxisAlignment: crossAxisAlignment,
textDirection: textDirection,
verticalDirection: verticalDirection,
textBaseline: textBaseline,
);
}
class _Flex extends Flex {
_Flex({
Key key,
Axis direction = Axis.vertical,
MainAxisAlignment mainAxisAlignment = MainAxisAlignment.start,
MainAxisSize mainAxisSize = MainAxisSize.max,
CrossAxisAlignment crossAxisAlignment = CrossAxisAlignment.center,
TextDirection textDirection,
VerticalDirection verticalDirection = VerticalDirection.down,
TextBaseline textBaseline,
List<Widget> children = const <Widget>[],
}) : super(
children: children,
key: key,
direction: direction,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: mainAxisSize,
crossAxisAlignment: crossAxisAlignment,
textDirection: textDirection,
verticalDirection: verticalDirection,
textBaseline: textBaseline,
);
@override
RenderFlex createRenderObject(BuildContext context) {
return _RenderFlex(
direction: direction,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: mainAxisSize,
crossAxisAlignment: crossAxisAlignment,
textDirection: getEffectiveTextDirection(context),
verticalDirection: verticalDirection,
textBaseline: textBaseline,
);
}
}
class _RenderFlex extends RenderFlex {
_RenderFlex({
List<RenderBox> children,
Axis direction = Axis.horizontal,
MainAxisSize mainAxisSize = MainAxisSize.max,
MainAxisAlignment mainAxisAlignment = MainAxisAlignment.start,
CrossAxisAlignment crossAxisAlignment = CrossAxisAlignment.center,
TextDirection textDirection,
VerticalDirection verticalDirection = VerticalDirection.down,
TextBaseline textBaseline,
}) : super(
children: children,
direction: direction,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: mainAxisSize,
crossAxisAlignment: crossAxisAlignment,
textDirection: textDirection,
verticalDirection: verticalDirection,
textBaseline: textBaseline);
double _getCrossSize(RenderBox child) {
switch (direction) {
case Axis.horizontal:
return child.size.height;
case Axis.vertical:
return child.size.width;
}
return null;
}
@override
void performLayout() {
super.performLayout();
var child = firstChild;
var crossSize = 0.0;
while (child != null) {
final childParentData = child.parentData as FlexParentData;
if (child is! RenderPositionedBox) {
crossSize = math.max(crossSize, _getCrossSize(child));
}
child = childParentData.nextSibling;
}
child = firstChild;
while (child != null) {
final childParentData = child.parentData as FlexParentData;
if (child is RenderPositionedBox) {
BoxConstraints innerConstraints = direction == Axis.horizontal
? BoxConstraints.tightFor(height: crossSize)
: BoxConstraints.tightFor(width: crossSize);
child.layout(innerConstraints, parentUsesSize: true);
} else {
double childCrossPosition = 0;
switch (crossAxisAlignment) {
case CrossAxisAlignment.start:
childCrossPosition = 0;
break;
case CrossAxisAlignment.end:
childCrossPosition = crossSize - _getCrossSize(child);
break;
case CrossAxisAlignment.center:
childCrossPosition = crossSize / 2.0 - _getCrossSize(child) / 2.0;
break;
case CrossAxisAlignment.stretch:
childCrossPosition = 0.0;
break;
case CrossAxisAlignment.baseline:
//TODO not supported yet
}
switch (direction) {
case Axis.horizontal:
childParentData.offset =
Offset(childParentData.offset.dx, childCrossPosition);
break;
case Axis.vertical:
childParentData.offset =
Offset(childCrossPosition, childParentData.offset.dy);
break;
}
}
child = childParentData.nextSibling;
}
size = constraints.constrain(direction == Axis.horizontal
? Size(size.width, crossSize)
: Size(crossSize, size.height));
}
}