JavaFx fx:id导致错误 [英] JavaFx fx:id causes error

问题描述

由于某种原因，我的fx:id无法正确绑定到我的Controller类，因此始终会导致错误.

For some reason, my fx:id does not bind properly to my Controller class, and thus always causes an error.

控制器

package sample;

import javafx.fxml.FXML;

import java.awt.*;
import java.awt.event.ActionEvent;

public class Controller {

    @FXML public Button button;

    public void clickAction(ActionEvent actionEvent) {
        System.out.println("Button clicked.");
    }
}

FXML

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<BorderPane fx:controller="sample.Controller" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
   <Button text="Click me!" fx:id="button" onAction="#clickAction" BorderPane.alignment="CENTER"/>
</BorderPane>

我认为我了解问题的根源，但我不知道如何正确解决该问题.根据这个问题的答案，我认为我我试图在调用构造函数之前分配FXML元素(这些元素只能在初始化期间/之后分配).

I think I understand the source of my problem, but I do not understand how to properly address it. According an answer of this question, I think I am trying to assign FXML elements before the constructor is called (and these elements can only be assigned during/after initialisation).

有没有一种方法可以在不实现Initializable的情况下实现 ?还是我犯了一个完全不同的错误?

Is there a way to do this without implementing Initializable? Or am I making a completely different mistake?

推荐答案

您使用导入

<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

在您的fxml文件中.

in your fxml file.

因此，在加载fxml文件时创建的Button实例是javafx.scene.control.Button.

Therefore the Button instance created while loading the fxml file is a javafx.scene.control.Button.

要注入的字段类型需要为javafx.scene.control.Button可以分配给的字段.

The type of the field this is injected to needs be something a javafx.scene.control.Button can be assigned to.

由于除了javafx.fxml.FXML之外，您在控制器中唯一的导入都是来自java.awt包，因此button字段(类型java.awt.Button)显然不是这种情况.

Since your only imports in the controller besides javafx.fxml.FXML are from the java.awt packages, this is clearly not the case for the button field (type java.awt.Button).

修复您的控制器，以从javafx软件包中导入所需的类:

Fix your controller to import the required classes from the javafx packages instead:

import javafx.fxml.FXML;

import javafx.scene.control.Button;
import javafx.event.ActionEvent;

BTW:如果您不使用onAction处理程序的参数，也可以不使用它:

BTW: You can also leave out the parameter of the onAction handler, if you do not use it:

public void clickAction() {
    System.out.println("Button clicked.");
}

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