自定义JavaFX控件 - "已指定的根值"在Scene Builder 2.0中

时间:2014-09-08 22:08:15

标签: java javafx javafx-8 scenebuilder

我使用fxml文件和Java类实现了一个自定义控件,类似于this official tutorial中的解释(参见下面的代码)。请注意,fxml根元素是使用fx:root定义的,我以编程方式调用setRoot

我尝试将控件包含在应用程序的FXML布局中,并且应用程序加载正常(并按预期显示控件)。

但是,如果我尝试在Scene Builder 2.0中导入包含我的控件的jar文件,则控件不会出现在要导入的组件列表中(与同一jar中的其他控件不同)。如果我选择"显示JAR分析报告",则会显示由javafx.fxml.LoadException: Root value already specified引起的错误。

您是否知道为什么在Scene Builder中加载时会出现此错误,即使它在实际应用程序中正确加载?

这是FXML:

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

<?import javafx.scene.control.*?>
<?import javafx.scene.image.ImageView?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.text.Font?>

<fx:root type="javafx.scene.layout.GridPane" id="MediaMetadataDisplay" hgap="20.0" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0"
         prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
    <columnConstraints>
        <ColumnConstraints fillWidth="false" hgrow="NEVER" maxWidth="-Infinity" minWidth="-Infinity" prefWidth="200.0"/>
        <ColumnConstraints halignment="LEFT" hgrow="ALWAYS"/>
    </columnConstraints>
    <rowConstraints>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="30.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="40.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="25.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="25.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="25.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="25.0" vgrow="SOMETIMES"/>
        <RowConstraints maxHeight="-Infinity" minHeight="-Infinity" prefHeight="30.0" vgrow="SOMETIMES"/>
    </rowConstraints>
    <children>
        <ImageView id="coverView" fx:id="coverView" fitHeight="200.0" fitWidth="200.0" pickOnBounds="true" preserveRatio="true" GridPane.rowSpan="7"/>
        <Label id="trackName" fx:id="trackName" maxWidth="1.7976931348623157E308" text="trackName" GridPane.columnIndex="1" GridPane.rowIndex="1">
            <font>
                <Font name="System Bold" size="16.0"/>
            </font>
        </Label>
        <Label id="artist" fx:id="artist" maxWidth="1.7976931348623157E308" text="artist" GridPane.columnIndex="1" GridPane.rowIndex="2"/>
        <Label id="album" fx:id="album" maxWidth="1.7976931348623157E308" text="album" GridPane.columnIndex="1" GridPane.rowIndex="3"/>
        <Label id="genre" fx:id="genre" maxWidth="1.7976931348623157E308" text="genre" GridPane.columnIndex="1" GridPane.rowIndex="4"/>
        <Label id="trackNumber" fx:id="trackNumber" maxWidth="1.7976931348623157E308" text="trackNumber" GridPane.columnIndex="1" GridPane.rowIndex="5"/>
    </children>
</fx:root>

Java控制器/根元素:

package customjavafx.scene.control;

import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Label;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.GridPane;
import javafx.scene.media.Media;

import java.io.IOException;
import java.util.Map;

public class MediaMetadataDisplay extends GridPane {

    public MediaMetadataDisplay() {
        final FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("MediaMetadataDisplay.fxml"));
        fxmlLoader.setRoot(this);
        fxmlLoader.setController(this);
        try {
            fxmlLoader.load();
        } catch (IOException exception) {
            throw new RuntimeException(exception);
        }

        media.addListener((obs, oldVal, newVal) -> updateMedia(newVal));
    }

    private final ObjectProperty<Media> media = new SimpleObjectProperty<>((Media) null, "media");
    @FXML private ImageView coverView;
    @FXML private Label trackName;
    @FXML private Label artist;
    @FXML private Label album;
    @FXML private Label genre;
    @FXML private Label trackNumber;

    public void updateMedia(Media media) {
        // TODO show updated metadata
    }

    public ObjectProperty<Media> mediaProperty() {
        return media;
    }
    public Media getMedia() {
        return mediaProperty().get();
    }
    public void setMedia(final Media media) {
        mediaProperty().set(media);
    }
}

错误的原因,在Scene Builder显示的堆栈跟踪中:

Caused by: javafx.fxml.LoadException: Root value already specified.
file:/Users/guillaumegaly/Library/Application%20Support/Scene%20Builder/Library/custom-controls_2.11.jar!/customjavafx/scene/control/MediaMetadataDisplay.fxml

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2613)
    at javafx.fxml.FXMLLoader.createElement(FXMLLoader.java:2771)
    at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2720)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
    at customjavafx.scene.control.MediaMetadataDisplay.<init>(MediaMetadataDisplay.java:26)
    ... 18 more

2 个答案:

答案 0 :(得分:7)

删除行

fxmlLoader.setRoot(this);

您的FXML将root定义为AnchorPane(并且您无法设置root两次,这就是您收到错误的原因)。

<fx:root type="javafx.scene.layout.GridPane" id="MediaMetadataDisplay" hgap="20.0" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0"
         prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">

我非常感谢这篇文章

Root value already specified

答案 1 :(得分:2)

我正在关注文档中的Javafx FXML教程,并且我被困在自定义组件部分。对我来说问题是,当我调用setRoot方法时,它会抛出“Root already specified”错误。就个人而言,我通过将根标记添加到自定义组件FXML文档中来修复此问题。它现在有效。

我正在添加此项,以便如果其他人遇到同样的问题,Google可以给他们答案。