我从FXML加载了一个Parent,将它添加到场景/舞台中的一个窗格并显示它,然后立即查找组件。 lookup()为某些人返回null,但对其他人返回非null。它会在什么情况下这样做?
这是加载和查找代码:
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返回OK,但随后它的所有子节点都返回null。
FXML加载:
<?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>
答案 0 :(得分:5)
在将CSS应用于场景之前,无法保证查找工作正常。这通常发生在第一次布局过程中(即第一次将场景图渲染到屏幕上),并且在某些情况下甚至可能在此之后发生。查找通常不推荐作为获取您在场景图中定义的节点的机制。
引用FXML中定义的控件的推荐方法是使用控制器类。将FXML中的所有id
属性更改为fx:id
属性,并将控制器类属性添加到根元素:
<BorderPane style="-fx-background-color: white;" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="com.my.company.PracticeScreenController">
<center>
<StackPane fx:id="scoreScreenStack" style="-fx-background-color: blue;" BorderPane.alignment="CENTER">
<children>
<ScrollPane fx:id="scoreScrollPane" fitToHeight="true" hbarPolicy="ALWAYS" vbarPolicy="NEVER">
<content>
<StackPane fx:id="scoreScrollStack">
<!-- etc -->
</StackPane>
</content>
</ScrollPane>
</children>
</StackPane>
</center>
</BorderPane>
现在定义一个带有相应@FXML
- 注释字段的控制器类。您可以在initialize()
方法中访问这些字段(注意在调用构造函数时它们不会被初始化):
package com.my.company ;
// imports...
public class PracticeScreenController {
@FXML
private StackPane scoreScreenStack ;
@FXML
private ScrollPane scoreScrollPane ;
@FXML
private ScrollPane scoreScrollStack ;
// etc...
public void initialize() {
// configure controls here, as needed...
}
}
如果迫切需要从加载FXML文件的位置检索FXML文件中定义的节点的引用,而不是在控制器中,则可以通过FXMLLoader
&#39;来执行此操作。命名空间。同样,我应该强调这是不是推荐的方法,你应该使用控制器类来访问它们,但这确实提供了另一种解决方案。
使用上面FXML中显示的相同fx:id
属性,您可以执行以下操作:
FXMLLoader loader = new FXMLLoader(getClass().getResource("PracticeScreen.fxml"));
rootUi = loader.load();
Map<String, Object> namespace = loader.getNamespace();
// added to Parent within stage and setVisible(true)
analysisGroup = (Pane)namespace.get("analysisGroup");
stickiesPane = (Pane)namespace.get("stickiesPane");
scoreScroll = (ScrollPane)namespace.get("scoreScrollPane");
tintLayer = (Pane)namespace.get("tintLayer");
scoreImageView = (ImageView)namespace.get("scoreImage");
StackPane scoreRenderStack = (StackPane)namespace.get("scoreRenderStack");
StackPane scoreScrollStack = (StackPane)namespace.get("scoreScrollStack");
答案 1 :(得分:1)
这是因为lookup()仅查看子项,而不是像ScoreScrollPane(ScrollPane)一样的“内容”。 ScrollPane的内容未包含在其子级中。此外,rootUi.getScene().lookup("#scoreScrollPane")
也返回null。你必须改为:
scoreImageView = (ImageView)scoreScroll.getContent().lookup("#scoreImage"); // GOOD now