maincontroller
package treetest;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.Button;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.input.MouseEvent;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
/**
*
* @author akhil kumar
*/
public class maincontroller {
@FXML
private GraphicsContext gc;
private Canvas canvas;
private TreeView<String> bro;
TreeItem<String> root=new TreeItem<>("root");
TreeItem<String> child = new TreeItem<>("child");
TreeItem<String> child2 = new TreeItem<>("child");
TreeItem<String> child3 = new TreeItem<>("child");
TreeItem<String> child4 = new TreeItem<>("child");
TreeItem<String> child5 = new TreeItem<>("child");
public void initialize(){
root.getChildren().add(child);
root.getChildren().add(child2);
root.getChildren().add(child3);
root.getChildren().add(child4);
root.getChildren().add(child5);
bro.setRoot(root);
bro.setShowRoot(false);
gc=canvas.getGraphicsContext2D();
gc.setFill(Color.WHITE);
gc.fillRect(0,0,canvas.getWidth(),canvas.getHeight());
}
}
fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.canvas.*?>
<?import javafx.geometry.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="600.0" minWidth="800.0" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="treetest.maincontroller">
<top>
<VBox BorderPane.alignment="CENTER">
<children>
<MenuBar>
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Edit">
<items>
<MenuItem mnemonicParsing="false" text="Delete" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Help">
<items>
<MenuItem mnemonicParsing="false" text="About" />
</items>
</Menu>
</menus>
</MenuBar>
<HBox>
<children>
<Button fx:id="catchment" mnemonicParsing="false" text="Button" />
<Button fx:id="output" mnemonicParsing="false" text="Button" />
<Button fx:id="junction" mnemonicParsing="false" text="Button" />
<Button fx:id="run" mnemonicParsing="false" text="Button" />
</children>
<padding>
<Insets bottom="10.0" left="10.0" top="10.0" />
</padding>
</HBox>
</children>
</VBox>
</top>
<center>
<Canvas fx:id="canvas" height="533.0" width="592.0" BorderPane.alignment="CENTER">
<cursor>
<Cursor fx:constant="CROSSHAIR" />
</cursor>
</Canvas>
</center>
<left>
<TreeView fx:id="bro" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
</left>
</BorderPane>
even though the fx : ids of the canvas and treeview are matching with the ones in the emain controller i am getting a null pointer exception
at the lines
bro.setRoot(root)
bro.setShowRoot(false);
gc=canvas.getGraphicsContext2D();
basically in any line itry to use the canvas and treeview i am getting a nullpointer exception
error log
file:/C:/Users/akhil%20kumar/Documents/NetBeansProjects/treetest/dist/run720357897/treetest.jar!/treetest/tree.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2571)
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 treetest.Treetest.start(Treetest.java:30)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
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 treetest.maincontroller.initialize(maincontroller.java:52)
... 27 more
what is wrong with my code ?
line 52 is
bro.setRoot(root);
the weird part is when i remove all the lines with the graphiccontext gc and the canvas in the initialise function it completly works fine.
this is specific too javafx of why the controller is not able to find the objects in the fxml file hence a general answer for nullpointer exceptions might not help me
not able to understand why this is happening ?
