java fx : scene's lookup method

Question

如果一个节点有 fx:id(比如 a)和正常的 id(css id)(比如 b)。如果使用 lookup 来搜索这个节点:

节点node=scene.lookup("#a")

以上语句返回null。但是如果讨论中没有对应节点的css id，那么上面的语句返回正确的节点。

虽然使用下面给定的语句总是返回正确的结果:

节点node=scene.lookup("#b")

谁能解释一下为什么查找方法的行为如此奇怪？

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.image.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.paint.*?>
<?import javafx.scene.text.*?>

<GridPane hgap="14.0" maxHeight="+Infinity" maxWidth="+Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="223.0" prefWidth="323.0" vgap="20.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
  <children>
    <VBox maxHeight="+Infinity" maxWidth="+Infinity" minHeight="-Infinity" spacing="7.0" GridPane.rowIndex="0">
      <children>
            <HBox alignment="TOP_RIGHT">
               <children>
              <Label fx:id="headerMessage" text="message" textAlignment="LEFT" wrapText="true">
                <font>
                  <Font name="System Bold" size="13.0" />
                </font>
              </Label>
               </children>
            </HBox>
            <HBox alignment="TOP_RIGHT" spacing="5.0">
               <children>
              <Label fx:id="qty" text="details" textAlignment="LEFT" wrapText="true">
                <font>
                  <Font size="12.0" />
                </font>
              </Label>
                  <TextField fx:id="qtyT" />
               </children>
            </HBox>
            <HBox alignment="TOP_RIGHT" spacing="5.0">
               <children>
                  <Label fx:id="name" text="details" textAlignment="LEFT" wrapText="true">
                     <font>
                        <Font size="12.0" />
                     </font>
                  </Label>
                  <TextField fx:id="nameT" />
               </children>
            </HBox>
            <HBox alignment="TOP_RIGHT" spacing="5.0">
               <children>
                  <Label fx:id="remarks" text="details" textAlignment="LEFT" wrapText="true">
                     <font>
                        <Font size="12.0" />
                     </font>
                  </Label>
                  <TextArea fx:id="remarksT" prefHeight="60.0" prefWidth="149.0" wrapText="true" />
               </children>
            </HBox>
      </children>
    </VBox>
    <HBox maxHeight="-Infinity" maxWidth="+Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="25.0" prefWidth="253.0" GridPane.rowIndex="1">
      <children>
        <Pane maxWidth="+Infinity" HBox.hgrow="ALWAYS" />
        <Button id="cancel-button" fx:id="cancelButton" cancelButton="true" minWidth="80.0" mnemonicParsing="false" text="Cancel" HBox.hgrow="NEVER">
          <HBox.margin>
            <Insets />
          </HBox.margin>
        </Button>
        <HBox fx:id="okParent" alignment="CENTER">
          <children>
            <Button id="ok-button" fx:id="okButton" minWidth="80.0" mnemonicParsing="false" text="Ok" HBox.hgrow="NEVER">
              <HBox.margin>
                <Insets left="14.0" />
              </HBox.margin>
            </Button>
          </children>
        </HBox>
      </children>
    </HBox>
  </children>
  <columnConstraints>
    <ColumnConstraints halignment="CENTER" hgrow="ALWAYS" maxWidth="+Infinity" minWidth="-Infinity" />
  </columnConstraints>
  <padding>
    <Insets bottom="14.0" left="14.0" right="14.0" top="14.0" />
  </padding>
  <rowConstraints>
    <RowConstraints maxHeight="+Infinity" minHeight="-Infinity" valignment="CENTER" vgrow="ALWAYS" />
    <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" vgrow="NEVER" />
  </rowConstraints>
</GridPane>

在上面的 fxml 中，对于没有任何 css id 的节点，查找在 fxml id 上工作正常。如果存在 css id，则返回空值

Label headerMessage = (Label) alertStage.getScene().lookup("#headerMessage");
                final TextField qty = (TextField) alertStage.getScene().lookup("#qtyT");
                Label name = (Label) alertStage.getScene().lookup("#name");
                final TextArea remarksT = (TextArea) alertStage.getScene().lookup("#remarksT");
                final TextField nameT = (TextField) alertStage.getScene().lookup("#nameT");

查找方法仅对下面给出的语句失败。

Button okButton = (Button) alertStage.getScene().lookup("#okButton");

Answer 1

编辑 - 在 OP 添加 MCVE 之后

深入研究这个问题。我在 FXML 文档的深处写了一个简单的声明，它解释了行为。实际上，通过调用 setId() 将 fx:id 指定为控件/布局的 默认 id。

除非被覆盖，fx:id 保持为对象的默认 id。

来自 Introduction To FXML :

Assigning an fx:id value to an element creates a variable in the document's namespace that can later be referred to by variable dereference attributes, such as the "toggleGroup" attribute shown above, or in script code, discussed in a later section. Additionally, if the object's type defines an "id" property, this value will also be passed to the objects setId() method.

lookup() 正在完美地完成它的工作，并且正在为 CSS 选择器 而不是 fx:id 工作。