您的 MainController 没有零参数构造函数.如果 FXMLLoader 在根元素上遇到 fx:controller 属性，它会尝试通过(有效地)调用类的零参数构造函数来创建该控制器的实例在属性中指定.

Your MainController doesn't have a zero-argument constructor. If the FXMLLoader encounters a fx:controller attribute on the root element, it attempts to create an instance of that controller by (effectively) calling the zero-argument constructor of the class specified in the attribute.

要解决此问题(最简单的方法)，从 FXML 文件中删除 fx:controller 属性，并在 上手动"设置控制器FXMLLoader.您需要创建一个 FXMLLoader 实例，而不是依赖于静态的 load(...) 方法:

To fix this (the simplest way), remove the fx:controller attribute from the FXML file, and set the controller "by hand" on the FXMLLoader. You need to create an FXMLLoader instance instead of relying on the static load(...) method:

FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
loader.setController(new MainController(path));
Pane mainPane = loader.load();