如何在animatedbuilder中返回null-safety？

Question

谁能帮我这个，我正在学习如何从技术人员花朵频道播放列表错误是下面的屏幕截图，我正在努力与零安全的事情，任何人可以解决这个问题。İ尝试使用空安全，但不能成功谢谢你??

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Answer 1

使用Container()在builder中包装您的child。

//...
builder: (BuildContext context, Widget? child) {
    return Container(child: child);
  },
//...

以下是如何使用AnimatedBuilder()的示例

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> with 
TickerProviderStateMixin {
  late final AnimationController _controller = AnimationController(
  duration: const Duration(seconds: 10),
  vsync: this,
)..repeat();
@override
Widget build(BuildContext context) {
  return AnimatedBuilder(
    // This widget wont rebuild.
    child: Container(
      child: Text("I can not rebuild weeeee.....!!!"), color: Colors.green),
  animation: _controller,
  builder: (BuildContext context, Widget? child) {
    return Transform.rotate(
      angle: _controller.value * 2.0 * math.pi,
      // here you will pass your widget
      child: child,
     );
    },
  );
 }
}