为什么80%的码农都做不了架构师？>>> 
自带AppBar 有限制
到app_bar.dart 中将 AppBar 和 _AppBarState 类复制到自定义的wAppBar 中
删除多余的Widget 保留样式参数
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';
//kToolbarHeight 状态栏的高度 包括刘海
class _ToolbarContainerLayout extends SingleChildLayoutDelegate {
const _ToolbarContainerLayout();
@override
BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
return constraints.tighten(height: kToolbarHeight);
}
@override
Size getSize(BoxConstraints constraints) {
return Size(constraints.maxWidth, kToolbarHeight);
}
@override
Offset getPositionForChild(Size size, Size childSize) {
return Offset(0.0, size.height - childSize.height);
}
@override
bool shouldRelayout(_ToolbarContainerLayout oldDelegate) => false;
}
class WAppBar extends StatefulWidget implements PreferredSizeWidget {
WAppBar({
Key key,
this.child, //自定义 widget 删除其他多余的wigdet
this.bottom,
this.elevation,
this.shape,
this.backgroundColor,
this.brightness,
this.iconTheme,
this.actionsIconTheme,
this.textTheme,
this.primary = true,
this.centerTitle,
this.titleSpacing = NavigationToolbar.kMiddleSpacing,
this.toolbarOpacity = 1.0,
this.bottomOpacity = 1.0,
}) : assert(elevation == null || elevation >= 0.0),
assert(primary != null),
assert(titleSpacing != null),
assert(toolbarOpacity != null),
assert(bottomOpacity != null),
preferredSize = Size.fromHeight(kToolbarHeight + (bottom?.preferredSize?.height ?? 0.0)),
super(key: key);
final Widget child;
final PreferredSizeWidget bottom;
final double elevation;
final ShapeBorder shape;
final Color backgroundColor;
final Brightness brightness;
final IconThemeData iconTheme;
final IconThemeData actionsIconTheme;
final TextTheme textTheme;
final bool primary;
final bool centerTitle;
final double titleSpacing;
final double toolbarOpacity;
final double bottomOpacity;
@override
final Size preferredSize;
@override
_WAppBarState createState() => _WAppBarState();
}
class _WAppBarState extends State {
static const double _defaultElevation = 0.0;
@override
Widget build(BuildContext context) {
assert(!widget.primary || debugCheckHasMediaQuery(context));
assert(debugCheckHasMaterialLocalizations(context));
final ThemeData themeData = Theme.of(context);
final AppBarTheme appBarTheme = AppBarTheme.of(context);
final ScaffoldState scaffold = Scaffold.of(context, nullOk: true);
final ModalRoute parentRoute = ModalRoute.of(context);
IconThemeData overallIconTheme = widget.iconTheme
?? appBarTheme.iconTheme
?? themeData.primaryIconTheme;
IconThemeData actionsIconTheme = widget.actionsIconTheme
?? appBarTheme.actionsIconTheme
?? overallIconTheme;
TextStyle centerStyle = widget.textTheme?.title
?? appBarTheme.textTheme?.title
?? themeData.primaryTextTheme.title;
TextStyle sideStyle = widget.textTheme?.body1
?? appBarTheme.textTheme?.body1
?? themeData.primaryTextTheme.body1;
print(sideStyle);
if (widget.toolbarOpacity != 1.0) {
final double opacity = const Interval(0.25, 1.0, curve: Curves.fastOutSlowIn).transform(widget.toolbarOpacity);
if (centerStyle?.color != null)
centerStyle = centerStyle.copyWith(color: centerStyle.color.withOpacity(opacity));
if (sideStyle?.color != null)
sideStyle = sideStyle.copyWith(color: sideStyle.color.withOpacity(opacity));
overallIconTheme = overallIconTheme.copyWith(
opacity: opacity * (overallIconTheme.opacity ?? 1.0)
);
actionsIconTheme = actionsIconTheme.copyWith(
opacity: opacity * (actionsIconTheme.opacity ?? 1.0)
);
}
Widget appBar = ClipRect(
child: CustomSingleChildLayout(
delegate: const _ToolbarContainerLayout(),
child: IconTheme.merge(
data: overallIconTheme,
child: DefaultTextStyle(
style: sideStyle,
// child: toolbar,
child: widget.child,
),
),
),
);
if (widget.bottom != null) {
appBar = Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Flexible(
child: ConstrainedBox(
constraints: const BoxConstraints(maxHeight: kToolbarHeight),
child: appBar,
),
),
widget.bottomOpacity == 1.0 ? widget.bottom : Opacity(
opacity: const Interval(0.25, 1.0, curve: Curves.fastOutSlowIn).transform(widget.bottomOpacity),
child: widget.bottom,
),
],
);
}
// The padding applies to the toolbar and tabbar, not the flexible space.
if (widget.primary) {
appBar = SafeArea(
top: true,
child: appBar,
);
}
appBar = Align(
alignment: Alignment.topCenter,
child: appBar,
);
final Brightness brightness = widget.brightness
?? appBarTheme.brightness
?? themeData.primaryColorBrightness;
final SystemUiOverlayStyle overlayStyle = brightness == Brightness.dark
? SystemUiOverlayStyle.light
: SystemUiOverlayStyle.dark;
return Semantics(
container: true,
child: AnnotatedRegion(
value: overlayStyle,
child: Material(
color: widget.backgroundColor
?? appBarTheme.color
?? themeData.primaryColor,
elevation: widget.elevation
?? appBarTheme.elevation
?? _defaultElevation,
shape: widget.shape,
child: Semantics(
explicitChildNodes: true,
child: appBar,
),
),
),
);
}
}
调用 自定义wAppBar
appBar: WAppBar(
child: new Container(
child: new Align(
child: Text("我是大标题",style: TextStyle(fontSize: 30.0),),
),
),
),
