Question

我是新手。我正在尝试创建自定义应用栏小部件，并将其导入页面。

但是我无法创建小部件。

`import 'package:flutter/material.dart';

 class AppBar extends StatelessWidget{
  @override
  Widget build(BuildContext context){
return AppBar(
  title: Text('Ordering'),
  actions: <Widget>[
    IconButton(
      onPressed: _incrementCounter,
      icon: Icon(Icons.add),
    ),
    BadgeIconButton(
      itemCount: _counter,
      badgeColor: Color.fromRGBO(37, 134, 16, 1.0),
      badgeTextColor: Colors.white,
      icon: Icon(Icons.shopping_cart, size: 30.0,),
      onPressed: () {}
    ),
  ],
);

} }'

Answer 1

import 'package:flutter/material.dart';

class CustomAppBar extends StatefulWidget implements PreferredSizeWidget {
    CustomAppBar({Key key}) : preferredSize = Size.fromHeight(56.0), super(key: key);

    @override
    final Size preferredSize; // default is 56.0

    @override
    _CustomAppBarState createState() => _CustomAppBarState();
}

class _CustomAppBarState extends State<CustomAppBar>{

    @override
    Widget build(BuildContext context) {
        return AppBar( title: Text("Sample App Bar") );
    }
}

希望这会有所帮助

Answer 2

finaldict = {22: [7, 9, 8]}
dict1 = {23: [7, 9, 8, 6, 12]}

Answer 3

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: true
  elevation: 0.0, // for elevation
  titleSpacing: 0.0, // if you want remove title spacing with back button
  title:  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 icon
  leading: new Material( //Custom leading icon, such as back icon or other icon
    color: 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))
      ),
  )
 );
}

希望，这会对您有所帮助。

Answer 4

编辑为riftninja的答案：

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>{

  @override
  Widget build(BuildContext context) {
    return AppBar( title: Text("Sample App Bar") );
  }
  }

这也适用于无状态小部件。

Answer 5

AppBar实现类PreferredSizeWidget，这意味着AppBar必须具有首选的大小。

preferredSize变量是从PreferredSizeWidget中实现的，因此会被覆盖，您可以在此处设置您希望的高度。

class CustomAppBar extends StatefulWidget implements PreferredSizeWidget {
  CustomAppBar({Key key}) : preferredSize = Size.fromHeight(60.0), super(key: key);

  @override
  final Size preferredSize;

  @override
  _CustomAppBarState createState() => _CustomAppBarState();
}

class _CustomAppBarState extends State<CustomAppBar>{

  @override
  Widget build(BuildContext context) {
    return AppBar(
      title: Text('App Bar'),
      actions: <Widget>[
        IconButton(
          icon: Icon(Icons.add, color: Colors.white,),
        ),
      ],
    );
  }
}

并像这样使用

class _MyHomePageState extends State<MyHomePage> {
  
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: CustomAppBar()
    );
  }

Answer 6

我使用自定义窗口小部件扩展了 AppBar 。然后将我的参数传递给 super类。

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

Answer 7

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,
  });

  @override
  Size get preferredSize => Size.fromHeight(height!);

  @override
  Widget 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,
    );
  }
}

如何使用？

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

Answer 8

屏幕截图（空安全）：

完整代码：

创建这个类。

class CustomAppBar extends StatelessWidget implements PreferredSizeWidget {
  final Widget child;
  final double height;

  CustomAppBar({
    required this.child,
    this.height = kToolbarHeight,
  });

  @override
  Size get preferredSize => Size.fromHeight(height);

  @override
  Widget build(BuildContext context) {
    return Container(
      height: preferredSize.height,
      color: Colors.red,
      child: child,
    );
  }
}

用法：

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

如何创建自定义AppBar小部件？

8 个答案:

屏幕截图（空安全）：

完整代码：