在Flutter中向下拖动时缩放内容

试试这个

CustomScrollView

LayoutBuilder(  builder: (context, constraints) {    return CustomScrollView(      slivers: <Widget>[        SliverPersistentHeader(          pinned: true,          delegate: Delegate(),        ),        SliverToBoxAdapter(          child: Container( decoration: BoxDecoration(   borderRadius:  BorderRadius.all(Radius.circular(30)),   border:  Border.all(     width: 2.0,     color:  Colors.deepPurple,   ), ), height: constraints.biggest.height, child: Center(   child: Text('Drag me down (or up) in order to see (or hide) the red icon on the top',     textAlign: TextAlign.center,     textScaleFactor: 5.0,   ), ),          ),        ),      ],    );  }),

“委托”类如下：

class Delegate extends SliverPersistentHeaderDelegate {  @override  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {    // print(shrinkOffset);    return Opacity(      opacity: 1 - shrinkOffset / maxExtent,      child: FittedBox(child: Icon(Icons.alarm, color: Colors.red,), fit: BoxFit.contain),    );  }  @override double get maxExtent => 300;  @override double get minExtent => 100;  @override bool shouldRebuild(SliverPersistentHeaderDelegate oldDelegate) => true;}

现在尝试上下拖动文本

编辑 ：这是一个小修改，类似于您的示例：

LayoutBuilder(  builder: (context, constraints) {    return CustomScrollView(      slivers: <Widget>[        SliverPersistentHeader(          pinned: true,          delegate: Delegate(),        ),        SliverToBoxAdapter(          child: Container( padding: EdgeInsets.only(top: 75), height: constraints.biggest.height, child: Text('Drag me down (or up) in order to make the red icon bigger (or smaller)',   textAlign: TextAlign.center,   textScaleFactor: 5.0, ),          ),        ),      ],    );  }),

和修改后的委托类：

class Delegate extends SliverPersistentHeaderDelegate {  @override  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {    // print(shrinkOffset);    return OverflowBox(      maxHeight: 400,      alignment: Alignment.topCenter,      child: Container(        height: 400 - shrinkOffset,        child:  FittedBox(child: Icon(Icons.alarm, color: Colors.red,), fit: BoxFit.contain),      ),     );  }  @override double get maxExtent => 300;  @override double get minExtent => 1;  @override bool shouldRebuild(SliverPersistentHeaderDelegate oldDelegate) => true;}