JavaFX - 手动将图像添加到GridPane

Question

我有以下设置

三个tic tac toe board是JavaFx中的gridpanes。

我正在尝试一种非常简单的方法，将ImageView添加到网格节点，以指示它是x还是o。

我正在做的代码是。

private void handleNewGameAction(ActionEvent event) throws IOException {

        FXMLLoader fxmlloader = new FXMLLoader(getClass().getResource("FXMLDocument.fxml"));

        GridPane pane = (GridPane)fxmlloader.getNamespace().get("topGrid");

        Image image = new Image("x.png");
        pane.add(new ImageView(image), 0, 0);

    }

我得到的错误是

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.control.MenuItem.fire(MenuItem.java:462)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$343(ContextMenuContent.java:1358)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 43 more
Caused by: java.lang.IllegalArgumentException: Invalid URL: Invalid URL or resource not found
    at javafx.scene.image.Image.validateUrl(Image.java:1118)
    at javafx.scene.image.Image.<init>(Image.java:620)
    at pkg3dtictactoe.FXMLDocumentController.handleNewGameAction(FXMLDocumentController.java:40)
    ... 53 more
Caused by: java.lang.IllegalArgumentException: Invalid URL or resource not found
    at javafx.scene.image.Image.validateUrl(Image.java:1110)
    ... 55 more

我真的很茫然，我一直在看堆栈溢出，看到的答案看起来和我写的完全一样，但我仍然得到上面的错误。

Answer 1

首先，为了回答当前问题，错误的最终原因由堆栈跟踪给出：

Caused by: java.lang.IllegalArgumentException: Invalid URL or resource not found
    at javafx.scene.image.Image.validateUrl(Image.java:1110)
    ... 55 more

这意味着您为"x.png"的构造函数提供的URL（Image）无效。您使用了错误的路径，或者资源不在您认为的位置。您在评论中提到您的图像文件与.java文件位于同一目录中。如果您使用的是Maven或Gradle，则资源的默认位置是src/main/resources（以及src/main/java文件的*.java）。如果这是一个纯NetBeans JavaFX项目（可能使用Ant？），我不知道资源应该去哪里。查看是否有为资源指定的目录，如果有，则移动所有资源文件。

您的代码还有其他一些问题：

private void handleNewGameAction(ActionEvent event) throws IOException {

    FXMLLoader fxmlloader = new FXMLLoader(getClass().getResource("FXMLDocument.fxml"));

    GridPane pane = (GridPane)fxmlloader.getNamespace().get("topGrid");

    Image image = new Image("x.png");
    pane.add(new ImageView(image), 0, 0);

}

第一期涉及fxmlloader.getNamespace().get("topGrid")。你在新创建的FXMLLoader上调用它，你还没有调用load()。这个调用的结果将始终是null，因为FXMLLoader实际上还没有实例化任何东西。

第二个，在我看来，更大的问题涉及每次调用此方法时创建新的GridPane的事实。这个新的GridPane永远不会添加到任何Scene，因此GUI将永远不会更新。需要明确的是，您在方法中检索的GridPane与已经显示的GridPane不同。当方法退出时，

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.image.ImageView;
import javafx.scene.layout.GridPane;

public class Controller {

  @FXML 
  private GridPane topGrid;

  @FXML
  private void handleAction(ActionEvent event) {
    topGrid.add(new ImageView(/*image*/), 0, 0);
    event.consume();
  }

}

超出范围并被垃圾收集。

由于您正在创建游戏板，因此您只需要加载一次（或者每次游戏一次）。之后，您使用加载的板添加图像。您应该使用与FXML文件链接的控制器类。

fx:controller

要将控制器链接到FXML文件，您可以使用文件中的FXMLLoader.setController(Object)属性，或者在调用实例load()方法之前使用FXMLLoader.getController()。要检索控制器，可以在调用load后使用Introduction to FXML。

要了解有关JavaFX中FXML的更多信息，请参阅qazxswpoi。