Thanks.
From the last screenshot, we can see that the NullPointerException points to line 29 of the NfcTagController.java file.
This line concerns readerStatusLabel, referring to a node that should exist in the NfcTagView.fxml file.
In JavaFX, the fxml file defines the Graphical User Interface. You can edit the fxml in a text editor or use Gluon's free SceneBuilder app for a GUI editor.
Unfortunately, it looks like the readerStatusLabel is not initialized, which could mean one of 2 things:
- readerStatusLabel is not defined in the fxml file -> open the NfcTagView.fxml file and check if you can see it.
- The fxml file has a syntax error that prevents it from loading. Seeing that the null pointer happens at the last line of initialize() instead of the first, this looks unlikely.
Reading the example guide again, I understand the problem now. The fxml file that is given at the beginning of the document does not contain the readerStatusLabel which is introduced in a later chapter. The guide is missing the update of the fxml file (It will be added in the next release, thanks to your intervention). For now, please replace your fxml file with this one:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<AnchorPane xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.st.myst25app.view.NfcTagController">
<children>
<GridPane hgap="5.0" layoutX="12.0" layoutY="87.0" AnchorPane.bottomAnchor="10.0" AnchorPane.leftAnchor="10.0" AnchorPane.rightAnchor="10.0" AnchorPane.topAnchor="10.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" maxWidth="284.0" minWidth="0.0" prefWidth="90.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="300.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Button fx:id="discoverButton" mnemonicParsing="false" prefWidth="90.0" text="Discover Tag" />
<Label text="Tag UID:" GridPane.halignment="RIGHT" GridPane.rowIndex="1" />
<Label fx:id="tagUidLabel" text="UID" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<Label text="EEPROM size:" GridPane.halignment="RIGHT" GridPane.rowIndex="2" />
<Label fx:id="tagSizeLabel" text="Size" GridPane.columnIndex="1" GridPane.rowIndex="2" />
<Button fx:id="writeNdefButton" mnemonicParsing="false" prefWidth="90.0" text="Write Uri" GridPane.rowIndex="3" />
<Label fx:id="writeStatusLabel" text="Status" GridPane.columnIndex="1" GridPane.rowIndex="3" />
<Label fx:id="readerStatusLabel" text="Reader Status" GridPane.columnIndex="1" GridPane.halignment="RIGHT" GridPane.rowIndex="4" />
<Label text="Detects Iso15693/NFC Forum Type 5 tag" GridPane.columnIndex="1" />
</children>
</GridPane>
</children>
</AnchorPane>
Cheers,
Damien
