How to create a custom AppBar widget?

class AppBars extends AppBar {AppBars():super(iconTheme: IconThemeData(color: Colors.black, //change your color here),backgroundColor: Colors.white,title: Text("this is app bar",style: TextStyle(color: Color(Constant.colorBlack)),),elevation: 0.0,automaticallyImplyLeading: false,actions: <Widget>[IconButton(icon: Icon(Icons.notifications),onPressed: () => null,),IconButton(icon: Icon(Icons.person),onPressed: () => null,),],);}

Widget build(BuildContext context) {return new Scaffold(appBar: setAppBar(),body: new Container() // add rest of the UI);}Widget setAppBar() {return new AppBar(//backgroundColor: Colors.blue,//automaticallyImplyLeading: trueelevation: 0.0, // for elevationtitleSpacing: 0.0, // if you want remove title spacing with back buttontitle: UtilCommonWidget.addTextMedium('About US', Colors.white, 20.0, 1),actions: <Widget>[addAppBarActionWidgetProfile(icon, 30.0, 30.0, 15.0) // add your custom action widget],//Action icon search as search icon, notification iconleading: new Material( //Custom leading icon, such as back icon or other iconcolor: Colors.transparent,child: new InkWell(onTap: () {Navigator.of(context).pop();},splashColor: UniQueryColors.colorGradientEnd.withOpacity(.5),child: new Container(padding: const EdgeInsets.fromLTRB(12.0, 16.0, 16.0, 16.0),child: UtilCommonWidget.addImage(Constant.iconBack, 19.0, 10.0))),));}

I extended AppBar with my custom widget.Then passed my parameters to the super class.

class CustomAppBar extends AppBar {CustomAppBar(): super(title: Text('MyApp'),actions: [IconButton(icon: Icon(Icons.search), onPressed: () {}),],);}

Screenshot (Null Safe):

Full code:

Create this class.

class CustomAppBar extends StatelessWidget implements PreferredSizeWidget {final Widget child;final double height;CustomAppBar({required this.child,this.height = kToolbarHeight,});@overrideSize get preferredSize => Size.fromHeight(height);@overrideWidget build(BuildContext context) {return Container(height: preferredSize.height,color: Colors.red,child: child,);}}

Usage:

Scaffold(appBar: CustomAppBar(height: 100,child: Column(children: [FlutterLogo(size: 56),SizedBox(height: 8),Text('Flutter'),],),),)

Edit to riftninja's answer :

import 'package:flutter/material.dart';class CustomAppBar extends StatefulWidget implements PreferredSizeWidget {CustomAppBar({Key key, double height}) : preferredSize = Size.fromHeight(height), super(key: key);@override//final Size preferredSize; // This didnot work for me.Size get preferredSize => preferredSize; //This should work.@override_CustomAppBarState createState() => _CustomAppBarState();}class _CustomAppBarState extends State<CustomAppBar>{@overrideWidget build(BuildContext context) {return AppBar( title: Text("Sample App Bar") );}}

This also works for stateless widget.

widget_appbar.dart

class WidgetAppBar extends StatelessWidget implements PreferredSizeWidget {final Color? backgroundColor;final Color? textIconColor;final String? icon;final String? title;final double? height;final List<Widget>? menuItem;final bool hideBack;WidgetAppBar({this.backgroundColor = whiteColor,this.textIconColor = headingColor,this.icon,this.title = '',this.menuItem,this.height: kToolbarHeight,this.hideBack = false,});@overrideSize get preferredSize => Size.fromHeight(height!);@overrideWidget build(BuildContext context) {return AppBar(actions: menuItem,toolbarHeight: preferredSize.height,iconTheme: IconThemeData(color: textIconColor,),leading: hideBack? Container(): icon == null? BackButton(): IconButton(icon: Image.asset(icon!,height: 18,width: 18,),onPressed: () {Navigator.pop(context, true);},),title: Text(title!,style: TextStyle(fontSize: 20,fontWeight: FontWeight.bold,color: textIconColor,),),backgroundColor: backgroundColor,centerTitle: true,);}}

How to use?

@overrideWidget build(BuildContext context) {return Scaffold(appBar: WidgetAppBar(icon: ic_back_black,title: 'Toolbar Title',),body: SafeArea(child: Container(),),);}