有问题创建一个javafx形状的二维数组，因为它不能分配值

Question

我已经看了一段时间，无法找到解决方案。基本上在Circle[][] board = new Circle[rows][column];行下面的代码给我提出了问题，当我尝试将这些值分配给这些圈时由于它们为空。我一直试图添加大括号像这个Circle[][] board = new Circle(0)[rows][column];，这将解决问题，但后来它说预期的阵列类型;发现javafx.scene.shape.Circle我添加了这个类的代码以及我的错误代码。如果需要任何其他代码，请通知我，并提前感谢您的帮助。码：

package com.company;


import javafx.event.ActionEvent;
import javafx.fxml.FXMLLoader;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class SetupBoard {

    public void main(Stage stage) {
        int rows = 8;
        int column = 8;
        Circle[][] board = new Circle[rows][column];
        int rowcounter = 0;
        int columncounter = 0;
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < column; j++) {
                board[i][j].setRadius(0);
            }
        }


            while (rowcounter < 3) {
                if (columncounter == 9) {
                    columncounter = 0;
                }
                if (columncounter == 8) {
                    columncounter = 1;
                }
                while (columncounter < 8) {
                    board[rowcounter][columncounter].setRadius(20);
                    columncounter = columncounter + 2;
                }
                rowcounter++;
            }

            rowcounter = 5;
            columncounter = 1;

            while (rowcounter < 8) {
                if (columncounter == 9) {
                    columncounter = 0;
                }
                if (columncounter == 8) {
                    columncounter = 1;
                }
                while (columncounter < 8) {
                    board[rowcounter][columncounter].setRadius(20);
                    columncounter = columncounter + 2;

                    int centrex;
                    int centrey;
                    centrex = 75 + (50 * rowcounter);
                    centrey = 125 + (50 * columncounter);

                    board[rowcounter][columncounter].setStroke(Color.BLUE);
                    board[rowcounter][columncounter].setFill(Color.BLUE);
                    board[rowcounter][columncounter].setCenterX(centrex);
                    board[rowcounter][columncounter].setCenterY(centrey);


                }
                rowcounter++;
            }


            for (int i = 0; i < rows; i++) {
                for (int j = 0; j < column; j++) {
                    //System.out.print(board[i][j]);
                    //Group root = new Group((board[i][j]));
                    //Scene scene = new Scene(root, 600, 600);
                    //stage.setScene(scene);
                    //stage.show();
                }
                System.out.println("");
            }

        }


    }

和错误：

> 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.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.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.Node.fireEvent(Node.java:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$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.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$MouseEventNotification.run(GlassViewEventHandler.java:352)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:388)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 48 more
Caused by: java.lang.NullPointerException
    at com.company.SetupBoard.main(SetupBoard.java:19)
    at com.company.Screens.MainWindow.BtnPress_start(MainWindow.java:25)
    ... 58 more*

Answer 1

Circle[][] board = new Circle[rows][column];

这里你刚刚初始化了数组。 这意味着你告诉JVM“嘿！看，我需要这个空间让我的元素存储在这里！”。 然后JVM通过给你一个指向该空间的指针来响应。每个矩阵位置代表该空白空间内的一个点。

 ____________________
| null | null | null |
|______|______|______|
| null | null | null |
|______|______|______|
| null | null | null |
|______|______|______|

---

for (int i = 0; i < rows; i++) {
   for (int j = 0; j < column; j++) {
      board[i][j].setRadius(0);
   }
}

在这里，您尝试将setRadius称为null引用，这是空白空间的默认有效值。在此之前，您需要以相同的方式初始化Circle（s）

for (int i = 0; i < rows; i++) {
   for (int j = 0; j < column; j++) {
      board[i][j] = new Circle();
   }
}