飞镖错误飞镖(argument_type_not_assignable) [英] flutter dart error dart(argument_type_not_assignable)

问题描述

以下对AnimationController的驱动器功能的调用会导致错误消息:

The following call to the drive function of the AnimationController leads to the error message:

不能将参数类型'ColorTween'分配给参数类型'Animatable'

The argument type 'ColorTween' can't be assigned to the parameter type 'Animatable'

Animation<Color> animation = animationController.drive(ColorTween(begin: Colors.red, end: colors.blue));

但是ColorTween是Tween< Color?>.Tween< T扩展了动态范围.是可动画的T.如何解决此错误?是个 '?'在颜色或动态"之后一个问题?显式强制转换也不起作用:

Yet ColorTween is a Tween<Color?> and Tween<T extends dynamic> is an Animatable<T>. How can I fix this error? Is the '?' after Color or 'dynamic' a problem? Explicit casting didn't work either:

类型'ColorTween'不是类型'Animatable< Color>'的子类型强制转换

type 'ColorTween' is not a subtype of type 'Animatable<Color>' in type cast

flutter 2.0.4 dart 2.12.2

推荐答案

赋值中 Animation 的 Color 类型缺少'?'因为 ColorTween 是 Tween< Color?> .

The Color type of the Animation in the assignment is missing the '?' as ColorTween is a Tween<Color?>.

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