如何从不同的控制器加载窗格到中间窗格的Vbox

Question

我有一个带有按钮的边界窗格，在顶部窗格中加载视图到边界窗格的左窗格中，然后在加载左窗格时，有一个按钮将视图加载到中心窗格中的vbox

Main.java

public class Main extends Application {
@Override
public void start(Stage stage) throws Exception{
//this is to load the parent (borderpane)
FXMLLoader loader = new FXMLLoader(getClass().getResource("/Views/fxml/main.fxml"));

//this is to create a controller for the parent view
loader.setController(new MainController());

Parent root = loader.load();

Scene scene = new Scene(root);
stage.setScene(scene);
stage.show;

/**
* @param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}

}

}

然后是Main MainController.java

public class MainController implements Initializable {

@FXML
protected BorderPane borderPane;
// This is a VBox occupying the Centerpane of the Borderpane
@FXML
protected VBox centerPane;
public MainController(){         
}

@Override
public void initialize(URL url, ResourceBundle rb) {

}    
// This loads the layout1 into the left pane of the borderpane from button handler inside the Top pane
@FXML
private void showLayout1(ActionEvent event) throws IOException {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource( "/Views/fxml/Layout1.fxml"));
loader.setController(new Controller1());
leftPane.getChildren().clear();
leftPane.getChildren().add(loader.load());
}

}

Layout1Controller.java

public class Layout1Controller implements Initializable{
private MainController app;

@Override
public void initialize(URL url, ResourceBundle rb){        
}

@FXML
private void ShowLayout2(ActionEvent event) throws IOException{
FXMLLoader loader2 = new FXMLLoader();
loader2.setLocation(getClass().getResource("/Views/fxml/Layout2.fxml"));
loader2.setController(new Controller2());
// This is returning a null causing a java.lang.NullPointerException
app.centerPane.getChildren().clear();      
app.centerPane.getChildren().add(loader2.load());  
}
}
}

Main.fxml

<BorderPane fx:id="border_pane" prefHeight="650.0" prefWidth="1018.0" style=" type="BorderPane" xmlns="http://javafx.com/javafx/8.0.141" xmlns:fx="http://javafx.com/fxml/1">
<left>
<VBox fx:id="leftPane" alignment="CENTER" prefHeight="569.0" prefWidth="215.0"  />
</left>
<center>
<VBox fx:id="centerPane" alignment="CENTER" prefHeight="586.0" prefWidth="701.0"  BorderPane.alignment="CENTER">
</VBox>
</center>
<top>
<HBox prefHeight="81.0" prefWidth="876.0" >
<children>
<Button fx:id="btnSGRE" mnemonicParsing="false" onAction="#ShowLayout1" prefHeight="26.0" prefWidth="151.0" style="-fx-background-color: transparent;" text="REVENUE ENTRIES" textFill="#11124a">
<font>
<Font name="Century" size="13.0" />
</font>
</Button>
</children>
</HBox>
</top>
</BorderPane>

Layout1.fxml

<AnchorPane prefHeight="565.0" prefWidth="215.0"  xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" >
<children>
<VBox alignment="BASELINE_CENTER" layoutY="40.0" prefHeight="415.0" prefWidth="215.0" >
<children>
<Text strokeType="OUTSIDE" strokeWidth="0.0" text="Revenue Entries">
<font>
<Font name="System Bold" size="18.0" />
</font>
</Text>
<HBox alignment="BASELINE_CENTER" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="35.0" prefWidth="173.0" >
<children>
<ComboBox fx:id="cmbRevGroup" onAction="#setCenters" prefHeight="35.0" prefWidth="195.0" promptText="Main Revenue Centers"/>
</children>
</HBox>
<HBox alignment="BASELINE_CENTER" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="35.0" prefWidth="173.0">
<children>
<ComboBox fx:id="cmbRevCent" onAction="#SelectedCenter" prefHeight="35.0" prefWidth="195.0" promptText="Revenue Centers"/>
<Button  mnemonicParsing="false" onAction="#ShowLayout2" prefHeight="43.0" prefWidth="142.0"  text="Revenue Entries" />
</children>
</HBox>
</children>
</VBox>
</AnchorPane>

现在，当我从Controller1访问主控制器中的VBox, centerPane时，它给了我一个空指针错误请帮助我如何将layout2从Controller1加载到centerPane

Answer 1

最后它能让centerPane加载layout2.fxml。所以我所要做的就是在ShowLayout1中创建Layout1Controller时为centerPane通过MainController创建一个get方法

MainController代码:

public class MainController implements Initializable {

@FXML
protected BorderPane borderPane;
// This is a VBox occupying the Centerpane of the Borderpane
@FXML
private VBox centerPane;

public VBox getCenterPane(){
return centerPane;
}
public MainController(){         
}

@Override
public void initialize(URL url, ResourceBundle rb) {

}    
// This loads the layout1 into the left pane of the borderpane from button handler inside the Top pane
@FXML
private void showLayout1(ActionEvent event) throws IOException {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource( "/Views/fxml/Layout1.fxml"));
loader.setController(new Controller1());
Layout1Controller controller = (Layout1Controller)loader.getController();
controller.setMainController(this);
leftPane.getChildren().clear();
leftPane.getChildren().add(loader.load());
}

}

Layout1Controller code:

public class Layout1Controller implements Initializable{
private MainController app;
public void setMainController(MainController app){
this.app = app;
}
@Override
public void initialize(URL url, ResourceBundle rb){        
}

@FXML
private void showLayout2(ActionEvent event) throws IOException{
FXMLLoader loader2 = new FXMLLoader();
loader2.setLocation(getClass().getResource("/Views/fxml/Layout2.fxml"));
loader2.setController(new Controller2());
// This is returning a null causing a java.lang.NullPointerException
app.getCenterPane().getChildren().clear();      
app.getCenterPane().getChildren().add(loader2.load());  
}
}
}