Я загрузил Parent из FXML, добавил его в панель в сцене / сцене и показал его, а затем сразу же посмотрел компоненты. lookup () возвращает null для некоторых, но не null для других. При каких обстоятельствах это сделало бы это?

Вот код загрузки и поиска:

    rootUi = FXMLLoader.load(getClass().getResource("PracticeScreen.fxml"));
    // added to Parent within stage and setVisible(true)
    analysisGroup = (Pane)rootUi.lookup("#analysisGroup");       // null
    stickiesPane = (Pane)rootUi.lookup("#stickiesPane");         // null
    scoreScroll = (ScrollPane)rootUi.lookup("#scoreScrollPane"); // GOOD
    tintLayer = rootUi.lookup("#tintLayer");                     // GOOD
    scoreImageView = (ImageView)rootUi.lookup("#scoreImage");    // null
    StackPane scoreRenderStack = (StackPane)rootUi.lookup("#scoreRenderStack"); // null
    StackPane scoreScrollStack = (StackPane)rootUi.lookup("#scoreScrollStack"); // null

ScoreScrollPane возвращается в порядке, но затем все его дочерние элементы возвращаются с нулевым значением.

FXML загружен:

  <?import javafx.geometry.Insets?>
  <?import javafx.scene.control.Label?>
  <?import javafx.scene.control.ScrollPane?>
  <?import javafx.scene.control.ToggleButton?>
  <?import javafx.scene.effect.DropShadow?>
  <?import javafx.scene.effect.Glow?>
  <?import javafx.scene.image.ImageView?>
  <?import javafx.scene.layout.*?>
  <?import javafx.scene.shape.Rectangle?>
  <?import javafx.scene.text.Font?>
  <BorderPane style="-fx-background-color: white;" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1">
     <center>
        <StackPane id="scoreScreenStack" style="-fx-background-color: blue;" BorderPane.alignment="CENTER">
           <children>
              <ScrollPane id="scoreScrollPane" fitToHeight="true" hbarPolicy="ALWAYS" vbarPolicy="NEVER">
                 <content>
                    <StackPane id="scoreScrollStack">
                       <children>
                          <StackPane id="scoreRenderStack" alignment="CENTER_LEFT" StackPane.alignment="CENTER_LEFT">
                             <children>
                                <ImageView id="scoreImage" pickOnBounds="true" preserveRatio="true" StackPane.alignment="CENTER_LEFT" />
                                <Pane id="analysisGroup" />
                                <Pane id="stickiesPane" minHeight="200.0" minWidth="200.0" />
                                <Rectangle id="playbackCursor" arcHeight="5.0" arcWidth="5.0" fill="DODGERBLUE" height="150.0" stroke="BLACK" strokeType="INSIDE" strokeWidth="0.0" visible="false" width="2.0">
                                   <effect>
                                      <DropShadow color="DODGERBLUE" />
                                   </effect>
                                </Rectangle>
                             </children>
                          </StackPane>
                       </children>
                    </StackPane>
                 </content>
              </ScrollPane>
              <BorderPane pickOnBounds="false">
                 <top>
                    <StackPane BorderPane.alignment="CENTER">
                       <children>
                          <BorderPane>
                             <left>
                                <Label id="recordingIndicator" text="Listening..." textFill="#00a7ff" BorderPane.alignment="CENTER">
                                   <font>
                                      <Font size="18.0" />
                                   </font>
                                   <effect>
                                      <Glow level="0.86" />
                                   </effect>
                                   <BorderPane.margin>
                                      <Insets />
                                   </BorderPane.margin>
                                   <padding>
                                      <Insets bottom="8.0" left="8.0" right="8.0" top="8.0" />
                                   </padding>
                                </Label>
                             </left>
                             <right>
                                <HBox BorderPane.alignment="CENTER">
                                   <children>
                                      <ToggleButton id="finalPerformance" mnemonicParsing="false" text="Final Performance" />
                                   </children>
                                   <BorderPane.margin>
                                      <Insets bottom="8.0" left="8.0" right="8.0" top="8.0" />
                                   </BorderPane.margin>
                                </HBox>
                             </right>
                          </BorderPane>
                       </children>
                    </StackPane>
                 </top>
              </BorderPane>
              <Pane id="tintLayer" opacity="0.0" pickOnBounds="false" style="-fx-background-color: #00a7ff;" visible="false" />
           </children>
        </StackPane>
     </center>
  </BorderPane>