JavaFx 元素未绑定(bind)到 fx :id 上的 Controller 变量

Question

这个问题已经有答案了:

JavaFX FXML controller - constructor vs initialize method (3 个回答)

已关闭 6 年前。

这可能是飞行员错误，但 FXML 属性未绑定(bind)到 fx:id 上的 Controller 类。我已将其缩减为一个微不足道的示例，但仍然“没有乐趣”。我忽略了什么？

FXML 文件...

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.BorderPane?>

<BorderPane fx:id="mainFrame" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.controller.BorderPaneCtrl">
  <left>
    <AnchorPane fx:id="anchorPaneLeft" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
  </left>
</BorderPane>

相关的Java代码是...

package sample.controller;

import javafx.fxml.FXML;
import javafx.scene.layout.AnchorPane;

public class BorderPaneCtrl {
    @FXML private AnchorPane anchorPaneLeft;

    public BorderPaneCtrl() {
        /* so, @FXML-annotated variables are accessible, but not
         *   yet populated
         */
        if (anchorPaneLeft == null) {
            System.out.println("anchorPaneLeft is null");
        }
    }

/* this is what was missing...added for "completeness"
 */
@FXML
public void initialize() {
    /* anchorPaneLeft has now been populated, so it's now
     *   usable
     */
    if (anchorPaneLeft != null) {
        // do cool stuff
    }
}

self 在这里不是问题，我很确定我忽略了一些简单的事情。

Answer 1

FXML 元素尚未在构造函数中分配，但您可以使用已分配元素的 Initialized 接口(interface)。

public class Controller implements Initializable {
    @FXML
    AnchorPane anchorPaneLeft;

    public Controller() {
        System.out.println(anchorPaneLeft); //null
    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        System.out.println(anchorPaneLeft); //AnchorPane
    }
}

我假设您知道应该使用 FXML 创建 Controller ，例如:FXMLLoader.load(getClass().getResource("sample.fxml");