Why I can not use FXML with Controllers and fxid in controller? - javafx

Question

I found here what I need. I need access from 1 Controller to another.
But I have a question. Why when I use FXML annotaion I get exception?
I want to make
public class MainController {
#FXML Tab1Controller tab1Controller;
#FXML Tab2Controller tab2Controller;
#FXML Tab tab1; //THIS
#FXML Tab tab2; // And this call exception. But if i comment both fields is evertying OK.
#FXML public void initialize() {
System.out.println("Application started");
tab1Controller.init(this);
tab2Controller.init(this);
}
public String loadLblTextFromTab1() {
return tab1Controller.lbl1.getText();
}
public void setTab2LabelText(String text) {
tab2Controller.lbl2.setText(text);
}
}
P.S add the XML file where I have that fx:id
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="299.0" prefWidth="309.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<children>
<TabPane prefHeight="299.0" prefWidth="309.0" tabClosingPolicy="UNAVAILABLE" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<tabs>
<Tab closable="false" text="Tab 1">
<content>
<fx:include fx:id="tab1" source="tab/Tab1.fxml" />
</content></Tab>
<Tab closable="false" text="Tab 2">
<content>
<fx:include fx:id="tab2" source="tab/Tab2.fxml" />
</content></Tab>
</tabs>
</TabPane>
</children>
</AnchorPane>
PSS.
If I use my FXML and Class like this I will get NullPointerException because of tab1Controller == null
public class MainController {
#FXML Tab tab1;
#FXML Tab1Controller tab1Controller;
#FXML public void initialize() {
tab1Controller.init(this); // Line 15
}
}
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="controller.MainController">
<TabPane>
<Tab fx:id="tab1" closable="false" text="Tab 1">
<fx:include source="tab/Tab1.fxml"/>
</Tab>
</TabPane>
</AnchorPane>
Exception looks like
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2566)
... 17 more
Caused by: java.lang.NullPointerException
at controller.MainController.initialize(MainController.java:15)
... 27 more
So, now I can not understand why I get that exception? Anyway I generated my Tab from fxml file itself.

Answer 1

The error message:
Caused by: java.lang.IllegalArgumentException:
Can not set javafx.scene.control.Tab field controller.MainController.tab1 to javafx.scene.layout.AnchorPane
explains what the problem is. The <fx:include> generates an AnchorPane (presumably that is the root element of Tab1.fxml), and you are trying to use a field of type Tab to reference it.
If you only need access to the content of the tab, just change the type of the field accordingly:
public class MainController {
#FXML Tab1Controller tab1Controller;
#FXML Tab2Controller tab2Controller;
#FXML AnchorPane tab1;
#FXML AnchorPane tab2;
#FXML public void initialize() {
System.out.println("Application started");
tab1Controller.init(this);
tab2Controller.init(this);
}
public String loadLblTextFromTab1() {
return tab1Controller.lbl1.getText();
}
public void setTab2LabelText(String text) {
tab2Controller.lbl2.setText(text);
}
}
If you specifically need access to the tabs themselves, then you'll need fx:ids on the Tab. As before, to get a reference to the controller, you need an fx:id on the <fx:include>. So if you want an actual reference to the Tab as well as to the controller, you will need (different) fx:ids on both the Tab and the <fx:include>:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="299.0" prefWidth="309.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<children>
<TabPane prefHeight="299.0" prefWidth="309.0" tabClosingPolicy="UNAVAILABLE" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<tabs>
<Tab fx:id="tab1" closable="false" text="Tab 1">
<content>
<fx:include fx:id="tab1Content" source="tab/Tab1.fxml" />
</content></Tab>
<Tab fx:id="tab2" closable="false" text="Tab 2">
<content>
<fx:include fx:id="tab2Content" source="tab/Tab2.fxml" />
</content></Tab>
</tabs>
</TabPane>
</children>
</AnchorPane>
and
public class MainController {
#FXML Tab1Controller tab1ContentController;
#FXML Tab2Controller tab2ContentController;
#FXML Tab tab1;
#FXML Tab tab2;
#FXML public void initialize() {
System.out.println("Application started");
tab1Controller.init(this);
tab2Controller.init(this);
}
public String loadLblTextFromTab1() {
return tab1ContentController.lbl1.getText();
}
public void setTab2LabelText(String text) {
tab2ContentController.lbl2.setText(text);
}
}