Java経由でグリッドペインにラベルを追加したかったのです。したがって、次のコードを使用しました。
public class Controller {
@FXML
private Button addTeam;
private GridPane teams;
public void addTeam(ActionEvent e) throws Exception {
if(e.getSource()==addTeam) {
Label apple = new Label("hello");
teams.setConstraints(apple, 0, 0);
teams.getChildren().add(apple);
}
}
コードを実行すると、InvocationTargetException にラップされた NullPointerException が発生します。
ここでnullとは正確には何ですか？私の現在の理解では、「@FXML」タグは、その下で宣言した変数をインスタンス化します。
スタック：
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java
.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown So
urce)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unkn
own Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknow
n Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknow
n Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(U
nknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Node.fireEvent(Unknown Source)
at javafx.scene.control.Button.fire(Unknown Source)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Un
known Source)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown S
ource)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown S
ource)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.h
andleBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unkn
own Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknow
n Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknow
n Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(U
nknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Sourc
e)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Sou
rce)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene$MouseHandler.process(Unknown Source)
at javafx.scene.Scene$MouseHandler.access$1500(Unknown Source)
at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotificatio
n.run(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotificatio
n.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEve
nt$355(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown
Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unkn
own Source)
at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.notifyMouse(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$149(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
... 61 more
Caused by: java.lang.NullPointerException
at GuiController.addTeam(GuiController.java:42)
... 70 more