getChildren（）.AddAll（）出现异常

Question

我正在尝试制作一个创建棋盘格的javafx程序。但是，当我尝试运行我的程序时，它在这一行中抛出异常：optionsPane.getChildren（）.addAll（optionsPane,n_input,grid_display,label,createButton）；这些是例外情况：

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class DD_CheckerBoard extends Application {

    Scene scene1, scene2; //2 scenes created to pass from a scene to another scene when create a checkerboard is clicked

    @Override
    public void start(Stage primaryStage) throws Exception{

        primaryStage.setTitle("My Checkerboard");

        //Scene 1
        HBox optionsPane = new HBox(10);
        optionsPane.setAlignment(Pos.CENTER); //sets alignment
        TextField n_input = new TextField(); //gets n from the user
        TextField grid_display = new TextField(); //only displays n x n
        grid_display.setEditable(false);
        Label label = new Label("Enter a single number to customize grid size.");
        Button createButton = new Button("Create New Checkerboard"); //button to create the new grid for checkerboard
        createButton.setOnAction(e-> primaryStage.setScene(scene2)); //calls checkerboard to the scene
        optionsPane.getChildren().addAll(optionsPane, n_input, grid_display, label, createButton); //add components
        scene1 = new Scene(optionsPane, 300,250); //create scene 1 for optionsPane

        //Scene 2
        getCheckerBoard(n_input); //create the checkerboard using the input from the user

        //SET SCENE
            primaryStage.setScene(scene1); // Place in scene in the stage, first scene is for the option pane
            primaryStage.show(); // Display the stage;
        }

    /**
     * And this method creates the checkerboard
     * @param input n by the user
     */
    public void getCheckerBoard(TextField input) {
            GridPane checkerboardPane = new GridPane(); //create a grid pane
            int n = Integer.parseInt(input.getText()); //parse input n to int
            int count = 0; //keep count of rectangles
            double s = 70; // side of rectangle
            for (int i = 0; i < n; i++) { //create the grid and rectangles
                count++; //increment count
                for (int j = 0; j < n; j++) {
                    Rectangle r = new Rectangle(s, s, s, s);
                    if (count % 2 == 0) r.setFill(Color.BLACK); //put rectangles to assigned colors in order
                    else r.setFill(Color.WHITE);
                    checkerboardPane.add(r, j, i); //add components to checkerboard
                    count++; //increment count
                } }
            scene2 = new Scene(checkerboardPane); //Create scene 2
         }

    public static void main(String[] args) throws Exception{
        launch(args);
    }
}

Answer 1

您正在尝试将optionspane作为子级添加到自身：

optionsPane.getChildren().addAll(optionsPane, n_input, grid_display, label, createButton);

这会导致您得到的异常。要解决此问题，只需从子级列表中删除optionspane:

optionsPane.getChildren().addAll(n_input, grid_display, label, createButton);

但是您还会得到一个NumberFormatException,因为您的Textfield默认为空：

java.lang.NumberFormatException：对于输入字符串：“”

因此您可能应该为textfield设置一个默认值：

TextField n_input = new TextField("0");