初始化/ FXML注入期间的Nullpointer异常未按预期工作

我注意到我的一个控制器类中有一种奇怪的行为 . 其中一个组件未初始化 .

这是fxml：

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="500.0" prefWidth="712.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="modulartoolkit.ConfigWindowController">
    <children>
        <Label layoutX="14.0" layoutY="12.0" text="Processes:" />
        <Button fx:id="newProcessButton" layoutX="324.0" layoutY="82.0" mnemonicParsing="false" onAction="#handleNewProcessButtonAction" prefHeight="25.0" prefWidth="51.0" text="New" />
        <Button fx:id="editProcessButton" layoutX="324.0" layoutY="118.0" mnemonicParsing="false" onAction="#handleEditProcessButtonAction" prefHeight="25.0" prefWidth="51.0" text="Edit" />
        <Button fx:id="deleteProcessButton" layoutX="324.0" layoutY="154.0" mnemonicParsing="false" onAction="#handleDeleteProcessButtonAction" text="Delete" />
        <ListView fx:id="processListView" layoutX="14.0" layoutY="30.0" prefHeight="200.0" prefWidth="295.0" />
        <Label layoutX="14.0" layoutY="250.0" text="Available Modules:" />
        <Label layoutX="400.0" layoutY="250.0" text="Configured Modules:" />
        <ListView layoutX="397.0" layoutY="266.0" prefHeight="200.0" prefWidth="295.0" />
        <TreeView layoutX="14.0" layoutY="266.0" prefHeight="200.0" prefWidth="295.0" />
    </children>
</AnchorPane>

这将是控制器：

public class ConfigWindowController implements Initializable {

    private Database database;
    private final ObservableList processListData = FXCollections.observableArrayList();

    @FXML
    private Button newProcessButton;
    private Button editProcessButton;
    private Button deleteProcessButton;
    private ListView<String> processListView;

    /**
     * Initializes the controller class.
     *
     * @param url
     * @param rb
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        this.database = Database.getInstance();
        processListView.setItems(processListData);
    }

    @FXML
    private void handleNewProcessButtonAction(ActionEvent event) {
        System.out.println("new Process");
    }

    @FXML
    private void handleEditProcessButtonAction(ActionEvent event) {
        System.out.println("EDIT!");
    }

    @FXML
    private void handleDeleteProcessButtonAction(ActionEvent event) {
        System.out.println("DELETE!");
    }

}

一旦我启动应用程序，我得到 NullPointerException 因为 ListView 为空 . 我可以通过在 ListView 添加@FXML注释来修复它：

@FXML
private Button newProcessButton;
private Button editProcessButton;
private Button deleteProcessButton;
@FXML
private ListView<String> processListView;

如果我将 ListView 移动到声明的顶部，它也可以工作 . 在每种情况下，所有按钮都会被初始化 .

有人知道为什么会这样吗？我认为注释只需要在声明的开头 . 或者是否必须为每种类型的组件输入？