flutter开发报错The instance member ‘widget‘ can‘t be accessed in an initializer

文章目录

  • 问题描述
  • 问题原因
  • 解决方法

问题描述

The instance member ‘widget’ can’t be accessed in an initializer.

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问题原因

“The instance member ‘widget’ can’t be accessed in an initializer” 错误是因为在初始化器列表中(constructor initializer list)访问了 widget 成员。这是因为在构造函数的初始化器列表中,对象的属性(包括 widget)还没有被初始化,因此不能在这里访问它们。

有问题的源码

class CountdownTimer extends StatefulWidget {
  final int duration;
  final int numIterations;
  final int breakTime;

  const CountdownTimer({
    Key? key,
    required this.duration,
    required this.numIterations,
    required this.breakTime,
  }) : super(key: key);

  @override
  State createState() => _CountdownTimerState();
}

class _CountdownTimerState extends State {
  final String countDownMusic='assets/beat.mp3';
  final String restMusic='assets/piano.mp3';
  late Timer _timer;
  double _timeProgress = 1.0;
  double _numProgress = 1.0;
  int rounds = widget.numIterations;

解决方法

int rounds = widget.numIterations;

这一句增加一个late修饰符

late int rounds = widget.numIterations;

结束语
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