在Dart中获取NoSuchMethodError [英] Getting a NoSuchMethodError in Dart

问题描述

我对Dart还是很陌生，我曾经使用过C＃（通常是XNA），所以Dart有点不同，我不确定为什么会发生此错误。

I'm pretty new to Dart, and I'm used to working with C# (and XNA usually), so Dart is a little different, and I'm not sure why this error is happening.

double left = c.Position.x - (canvasDimensions.x * 0.5);

Position和canvasDimensions是我创建的一种类型，称为Vector2，它基本上包含两个数字x和y，我收到错误消息

the Position and canvasDimensions are a type I created, called Vector2, which basically contains 2 numbers, x and y, I am getting the error

NoSuchMethodError : method not found: '-'
Receiver: null
Arguments: [600.0]

不熟悉这种语言，我不确定为什么会这样，请帮忙，谢谢！

on the line shown, since I am not familiar with the language I am not sure why this is happening, please help, thanks!

推荐答案

在这里 c.Position.x 为 null 。在Dart中，对 null 调用方法（或您的情况下的运算符-）会导致 NoSuchMethodError 。

Here c.Position.x is null. In Dart calling a method (or an operator - in your case) on null leads to a NoSuchMethodError.

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