学习Flutter各种Widgets的项目，包含各种样例demo
- AbsorbPointer
- AlertDialog
- Align
- AnimatedBuilder
- AnimatedContainer
- AnimatedCrossFade
- AnimatedDefaultTextStyle
- AnimatedListState
- AnimatedModalBarrier (不太懂)
- AnimatedOpacity
- AnimatedPhysicalModel
- AnimatedPositioned
- AnimatedSize
- AnimatedWidget
- AnimatedWidgetBaseState
- Appbar
- AspectRatio
- AssetBundle
- BackdropFilter
- Baseline
- BottomNavigationBar
- BottomSheet
- ButtonBar
- Card
- Center
- Checkbox
- Chip
- CircularProgressIndicator
- ClipOval
- ClipPath
- ClipRect
- Column
- ConstrainedBox
- Container
- CupertinoActionSheet
- CupertinoActivityIndicator
- CupertinoAlertDialog
- CupertinoButton
- CupertinoDatePicker
- CupertinoDialog
- CupertinoDialogAction
- CupertinoFullscreenDialogTransition
- CupertinoNavigationBar
- CupertinoPageScaffold
- CupertinoPageTransition
- CupertinoPicker
- CupertinoPopupSurface
- CupertinoScrollbar
- CupertinoSegmentedControl
- CupertinoSlider
- CupertinoSwitch
- CupertinoTabBar
- CupertinoTabScaffold
- CupertinoTabView
- CupertinoTextField
- CupertinoTimerPicker
- CustomMultiChildLayout
- CustomPaint
- CustomScrollView
- CustomSingleChildLayout
- DataTable
- Date & Time Pickers
- DecoratedBox
- DecoratedBoxTransition
- DefaultTextStyle
- Dismissible
- Divider
- DragTarget
- Draggable
- Drawer
- DropdownButton
- ExcludeSemantics
- Expanded
- ExpansionPanel
- FadeTransition
- FittedBox
- FlatButton
- FloatingActionButton
- Flow
- FlutterLogo
- Form
- FormField
- FractionalTranslation
- FractionallySizedBox
- FutureBuilder
- GestureDetector
- GridView
- Hero
- Icon
- IconButton
- IgnorePointer
- Image
- IndexedStack
- IntrinsicHeight
- IntrinsicWidth
- LayoutBuilder
- LimitedBox
- LinearProgressIndicator
- ListBody
- ListTile
- ListView
- LongPressDraggable
- MaterialApp
- MediaQuery
- MergeSemantics
- Navigator
- NestedScrollView
- NotificationListener
- Offstage
- Opacity
- OverflowBox
- Padding
- PageView
- Placeholder
- PopupMenuButton
- PositionedTransition
- Radio
- RaisedButton
- RawImage
- RawKeyboardListener
- RefreshIndicator
- RichText
- RotatedBox
- RotationTransition
- Row
- Scaffold
- ScaleTransition
- ScrollConfiguration
- Scrollable
- Scrollbar
- Semantics
- SimpleDialog
- SingleChildScrollView
- SizeTransition
- SizedBox
- SizedOverflowBox
- SlideTransition
- Slider
- SliverAppBar
- SnackBar
- Stack
- Stepper
- StreamBuilder
- Switch
- TabBar
- TabBarView
- Table
- Text
- TextField
- Theme
- Tooltip
- Transform
- WidgetsApp
- Wrap