java - FXMLLoader.getController() 无论如何都返回 null

Question

我一直在为我的 JavaFX 学习做一个小应用程序。在应用程序中，我需要从主文件中单独获取 Controller ，所以我设计了这个:

public class DiceObserver implements Observer {

    FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
    public Controller controller = loader.<Controller>getController();

    Dice ov;
    public DiceObserver(Dice dice){
        this.ov = dice;
    }

    public void update(Observable o, Object arg) {
        int roll = ov.getLastValue().getRolledValue();
        System.out.println(roll);
        controller.updateBarChart(roll);
    }
}

FXML 文件:

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.chart.BarChart;
import javafx.scene.chart.XYChart;
import javafx.scene.control.Button;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;

import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;


public class Controller{
    @FXML public TextField freqText;
    @FXML public Slider freqSlider;
    @FXML public Button startButton;
    @FXML public Button endButton;
    @FXML public BarChart rollChart;
    @FXML public ImageView dicePic;
    XYChart.Series s1 = new XYChart.Series<>();
    XYChart.Series s2 = new XYChart.Series<>();
    XYChart.Series s3 = new XYChart.Series<>();
    XYChart.Series s4 = new XYChart.Series<>();
    XYChart.Series s5 = new XYChart.Series<>();
    XYChart.Series s6 = new XYChart.Series<>();
    Image side1 = new Image("Dice_Side_1.png");
    SimulationThread t = SimulationThread.getInstance();

    public void startSimulation(ActionEvent event) { // start the simulation
        t.start();
    }

    public void getNewFreqValue(ActionEvent event) {
        freqText.setText(String.valueOf(freqSlider.getValue()));
    }

    public void stopSimulation(ActionEvent event) {
        t.end();
    }

    public void updateBarChart(int diceRoll){
        System.out.println(diceRoll);
        int rollval = diceRoll;
        switch (rollval) {
            case 1:
                s1.getData().add(rollval);
                break;
            case 2:
                s2.getData().add(rollval);
                break;
            case 3:
                s3.getData().add(rollval);
                break;
            case 4:
                s4.getData().add(rollval);
                break;
            case 5:
                s5.getData().add(rollval);
                break;
            case 6:
                s6.getData().add(rollval);
                break;
        }
    }

    public void updateDicePic(int diceRoll){
        dicePic.setImage(side1);
    }

    public void initialize() {
    }
}

updateBarChart 方法位于 Controller 中。当我运行代码时，加载器有一个值，但 getcontroller 方法返回 null。我该如何解决这个问题？

Answer 1

它返回null，因为您尚未指定 Controller 。从您上面发布的代码来看，您的 Controller 和 FXML 彼此不知道。

调用:

loader.setController(yourControllerInstance);

示例:

https://github.com/SnakeDoc/superD/blob/master/src/com/vanomaly/superd/Main.java#L39

或者您必须在 FXML 文档(在根元素中)中指定 Controller :

<AnchorPane maxHeight="...".... fx:controller="sample.Controller">
    <HBox .... >
    ....

示例:

https://github.com/SnakeDoc/Narvaro/blob/master/src/resources/Narvaro.fxml#L13