'findAncestorStateOfType' 方法在 null 上被调用接收者：null 尝试调用：findAncestorStateOfType<NavigatorState>() 错误

如何解决'findAncestorStateOfType' 方法在 null 上被调用接收者：null 尝试调用：findAncestorStateOfType<NavigatorState>() 错误

谁能帮我解决这个问题？我正在关注有关动画径向菜单的网站编码教程。但是本教程没有展示如何通过按下 FloatingActionButton 导航到其他页面。于是，我自己试了一下，却出现了这个错误。

这是我的代码

class RadialAnimation extends StatelessWidget { 
final AnimationController controller;
RadialAnimation({Key key,this.controller})
  : scale = Tween<double>(
      begin: 1.5,end: 0.0,).animate(
      CurvedAnimation(parent: controller,curve: Curves.fastOutSlowIn),),translation = Tween<double>(
      begin: 0.0,end: 100.0,).animate(
      CurvedAnimation(
        parent: controller,curve: Curves.elasticOut,rotation = Tween<double>(
      begin: 0.0,end: 360.0,curve: Interval(
          0.0,0.7,super(key: key);

// final AnimationController controller;
final Animation<double> scale;
final Animation<double> translation;
final Animation<double> rotation;

build(context) {
return AnimatedBuilder(
    animation: controller,builder: (context,builder) {
      return Transform.rotate(
        angle: radians(rotation.value),child: Stack(
          alignment: Alignment.center,children: [
            _buildButton1(45,color: Colors.red,icon: FontAwesomeIcons.thumbtack),_buildButton2(180,icon: FontAwesomeIcons.fire),_buildButton3(315,icon: FontAwesomeIcons.bolt),Transform.scale(
              scale: scale.value - 1,child: FloatingActionButton(
                child: Icon(FontAwesomeIcons.timesCircle),onPressed: _close,Transform.scale(
              scale: scale.value,onPressed: _open,],);
    });
}

这是我尝试修改代码的地方。

_buildButton1(double angle,{Color color,IconData icon}) {
final double rad = radians(angle);
return Transform(
    transform: Matrix4.identity()
      ..translate(
        (translation.value) * cos(rad),(translation.value) * sin(rad),child: FloatingActionButton(
      child: Icon(icon),backgroundColor: color,onPressed: () {
        BuildContext context;
        Navigator.push(
          context,MaterialPageRoute(builder: (context) => BT()),);
      },));
   }

解决方法

每次构建新按钮时，传递一个 context。无论您走到哪里，始终保持 context 的安全。

// Add a context as a parameter. Keep it safe.
_buildButton1(BuildContext context,double angle,{Color color,IconData icon}) {
  return Transform(
    # ...
    child: FloatingActionButton(
      child: Icon(icon),backgroundColor: color,onPressed: () {
        // No,that's wrong. Comment it,or even delete it FOREVER
        // BuildContext context;
        Navigator.push(context,MaterialPageRoute(builder: (context) => BT()));
      },),);
}

当您调用 _buildButton1 时，只需传递上下文。保持安全。

build(context) {
  return AnimatedBuilder(
    animation: controller,builder: (context,builder) {
      // Here's your context. Use it. Keep it safe.
      return Transform.rotate(
        angle: radians(rotation.value),child: Stack(
          alignment: Alignment.center,children: [
            // Use it. Keep it safe.
            _buildButton1(context,45,color: Colors.red,icon: FontAwesomeIcons.thumbtack),_buildButton2(context,180,icon: FontAwesomeIcons.fire),_buildButton3(context,315,icon: FontAwesomeIcons.bolt),Transform.scale(
              scale: scale.value - 1,child: FloatingActionButton(
                child: Icon(FontAwesomeIcons.timesCircle),onPressed: _close,Transform.scale(
              scale: scale.value,onPressed: _open,],);
    });
}