flutter dart 小功能记录

单例

class Singleton {
  Singleton._();
  static final instance = Singleton._();
}

AppBar 修改高度

设置AppBar的height

使用PreferredSize：

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Example',
      home: Scaffold(
        appBar: PreferredSize(
          preferredSize: Size.fromHeight(50.0), // here the desired height
          child: AppBar(
            // ...
          )
        ),
        body: // ...
      )
    );
  }
}

刷新报错

setState() or markNeedsBuild() called during build

WidgetsBinding.instance.addPostFrameCallback((_){
    _model.setOpacity(opacity);
});

setState() called after dispose()

if (!mounted) return;
setState(() {
  // do somthing
});

相机预览 高度填充

FittedBox(
              fit: BoxFit.fitHeight,
              child: SizedBox(
                width: _controller.value.aspectRatio,
                height: 1,
                child: CameraPreview(_controller),
              ),
            )

Android 下去除滚动波纹动画

NotificationListener(
                  onNotification: (notification) {
                    notification.disallowGlow();
                    return false;
                  },
  child: xxxxx
}

  bool _handleGlowNotification(OverscrollIndicatorNotification notification) {
    if (notification.depth != 0 || !notification.leading) return false;

    notification.disallowGlow();
    return false;
  }

Row/Column 宽度/高度 Wrap_content

    return Column(
      mainAxisSize: MainAxisSize.min,
      children: widgets,
    );

https://stackoverflow.com/questions/42257668/the-equivalent-of-wrap-content-and-match-parent-in-flutter

键盘弹出导致 overflow 处理方法

1. scaffold: resizeToAvoidBottomPadding: false,
2. SingleChildScrollView 包裹 Column

添加图片资源

添加 images 下的所有图片

  assets:
    - assets/images/

Splash 页面跳转问题

使用

Navigator.pushNamedAndRemoveUntil(context, ’/home‘ , (_) => false);

表示跳转到新页面，并且清理之前 router 中的所有历史页面。

计时器

3s 后执行某段代码：

Timer(Duration(seconds: 3), () {
  print("Yeah, this line is printed after 3 seconds");
});

重复执行循环执行:

Timer.periodic(Duration(seconds: 5), (timer) {
  print(DateTime.now());
});