问题
I created a card like pane so that I can add data to it and create a page with many cards according to data (much like a card layout in mobile applications) however, I don't know how to add new instances of this to VBox. I tired with and without a loop and still didn't work. It Keeps Giving the Following Error:
javafx.fxml.LoadException:
/C:///////bin/application/HotelReservation.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at application.Main.start(Main.java:18)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException: Children: child node is null: parent = VBox[id=vboxData]
at javafx.scene.Parent$2.onProposedChange(Parent.java:435)
at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:206)
at application.HotelReservationController.initialize(HotelReservationController.java:45)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
... 17 more
Here is the FXML File For the Card like Pane:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.image.ImageView?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.text.Font?>
<?import javafx.scene.text.Text?>
<AnchorPane fx:id="cardAnchor" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1">
<children>
<HBox fx:id="cardHBox" prefHeight="152.0" prefWidth="584.0">
<children>
<ImageView fx:id="cardPhoto" fitHeight="150.0" fitWidth="200.0" pickOnBounds="true" preserveRatio="true" />
<VBox prefHeight="200.0" prefWidth="100.0">
<children>
<Text fx:id="cardTitle" strokeType="OUTSIDE" strokeWidth="0.0" text="Ttile:" wrappingWidth="385.9830722808838">
<font>
<Font name="System Bold" size="31.0" />
</font>
</Text>
<HBox prefHeight="18.0" prefWidth="386.0">
<children>
<Text fx:id="cardLocation" strokeType="OUTSIDE" strokeWidth="0.0" text="Location:" wrappingWidth="211.9830722808838">
<font>
<Font name="System Bold" size="15.0" />
</font>
</Text>
<Text fx:id="cardRating" strokeType="OUTSIDE" strokeWidth="0.0" text="Rating:" wrappingWidth="172.9830722808838">
<font>
<Font name="System Bold" size="15.0" />
</font>
</Text>
</children>
</HBox>
<HBox prefHeight="100.0" prefWidth="200.0">
<children>
<Text fx:id="cardDescription" strokeType="OUTSIDE" strokeWidth="0.0" wrappingWidth="308.9830722808838" />
<Button fx:id="cardDetails" mnemonicParsing="false" prefHeight="89.0" prefWidth="79.0" text="Details" textAlignment="JUSTIFY" />
</children>
</HBox>
</children>
</VBox>
</children>
</HBox>
</children>
</AnchorPane>
and here is the FXML for where the VBox is located:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ScrollPane?>
<?import javafx.scene.control.SplitPane?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="700.0" prefWidth="700.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.HotelReservationController">
<children>
<SplitPane dividerPositions="0.14630681818181818" layoutX="-2.0" layoutY="-2.0" orientation="VERTICAL" prefHeight="706.0" prefWidth="708.0">
<items>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="85.0" prefWidth="162.0" style="-fx-background-color: brown;">
<children>
<HBox layoutX="2.0" prefHeight="100.0" prefWidth="248.0" spacing="2.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="75.0">
<children>
<Button mnemonicParsing="false" style="-fx-background-color: #EE854E;" text="Home" />
<Button mnemonicParsing="false" style="-fx-background-color: #EE854E;" text="Hotels" />
<Button mnemonicParsing="false" style="-fx-background-color: #EE854E;" text="Cars" />
<Button mnemonicParsing="false" style="-fx-background-color: #EE854E;" text="Trips" />
</children>
</HBox>
</children>
</AnchorPane>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="508.0" prefWidth="673.0" style="-fx-background-color: orange;">
<children>
<ScrollPane fx:id="scrollPaneContent" layoutX="-1.0" layoutY="-2.0" prefHeight="605.0" prefWidth="708.0" style="-fx-background-color: orange;" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<content>
<VBox fx:id="vboxData" prefHeight="176.0" prefWidth="705.0" style="-fx-background-color: orange;" />
</content></ScrollPane>
</children></AnchorPane>
</items>
</SplitPane>
</children>
</AnchorPane>
and here is how I implemented it in java:
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
public class Main extends Application {
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) {
try {
AnchorPane root =(AnchorPane) FXMLLoader.load(Main.class.getResource("/application/HotelReservation.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.setTitle("Hotel Reservation");
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
}
......
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
public class HotelReservationController implements Initializable{
@FXML
private ScrollPane scrollPaneContent;
@FXML
private VBox vboxData;
@FXML
private AnchorPane cardAnchor;
@FXML
private HBox cardHBox;
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
// TODO Auto-generated method stub
vboxData.setSpacing(5);
vboxData.getChildren().add(cardAnchor);
// for (int j = 0; j < 100; j++) {
// vboxData.getChildren().add(cardAnchor);
// }
}
回答1:
There is no element in HotelReservation.fxml with fx:id="cardAnchor", so cardAnchor is null in the controller, and you get the null pointer exception shown in your stack trace.
To "create instances of a FXML", you need to load the FXML. So I think what you are trying to do here is:
public class HotelReservationController implements Initializable{
@FXML
private ScrollPane scrollPaneContent;
@FXML
private VBox vboxData;
@FXML
private HBox cardHBox;
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
// unclear why you wouldn't do this in the FXML
vboxData.setSpacing(5);
// guessing at the path, will need to be set appropriately:
URL cardURL = getClass().getResource("/application/Card.fxml");
try {
for (int j = 0; j < 100; j++) {
Parent cardAnchor = FXMLLoader.load(cardURL);
vboxData.getChildren().add(cardAnchor);
}
} catch (IOException exc) {
exc.printStackTrace();
System.exit(1);
}
}
}
来源：https://stackoverflow.com/questions/65340356/javafx-fxmlhow-to-create-new-instances-of-a-self-made-fxml-to-vbox