使用 GUI 计算斐波那契方法

Question

我正在尝试使用斐波那契方法绑定到按钮，该方法将使用滑块作为输入值，然后在文本字段中打印斐波那契数。我在将值从我的斐波那契方法传递到文本字段时遇到了麻烦。任何帮助，将不胜感激。这是我到目前为止所写的：

public class Main extends Application {

    private static Slider fibSlider = new Slider(0, 10, 0);
    private static Label indexLabel = new Label();
    private static Label fibNumLabel = new Label();
    private static int colIndex = 0;
    private static int rowIndex = 0;
    private static int topIndex = 0;
    private static int rightIndex = 0;
    private static int leftIndex = 0;
    private static int bottomIndex = 0;
    private static TextField tfIndex;
    private static TextField tfFibNum;
    private static Button butCalcFib = new Button();

    @Override
    public void start(Stage primaryStage) {

        fibSlider.setMajorTickUnit(1);
        fibSlider.setMinorTickCount(0);
        fibSlider.setShowTickLabels(true);
        fibSlider.setShowTickMarks(true);
        fibSlider.setSnapToTicks(true);

        fibSlider.valueProperty().addListener(sl -> {
            tfIndex.setText(Double.toString(fibSlider.getValue()));
        });

        indexLabel.setText("Index: ");
        fibNumLabel.setText("Fibonacci #: ");
        butCalcFib.setText("Calculate Fibonacci");
        //tfFibNum.setText(long.toString(ComputeFibonacci()));

        fibSlider.valueProperty().addListener(new ChangeListener<Number>() {
            @Override
            public void changed(ObservableValue<? extends Number> observableValue, Number oldValue, Number newValue) {
                if (newValue == null) {
                    tfIndex.setText("");
                    return;
                }
                tfIndex.setText(Math.round(newValue.intValue()) + "");
            }
        });

        GridPane mainGPane = buildGPane();
        Scene mainScene = new Scene(mainGPane, 500, 200);

        primaryStage.setTitle(" - Fibonacci Calculator");
        primaryStage.setScene(mainScene);
        primaryStage.show();

    }

    private GridPane buildGPane() {
        GridPane gPane = new GridPane();
        gPane.setAlignment(Pos.CENTER);
        gPane.setPadding(new Insets(topIndex = 10, rightIndex = 10,
            bottomIndex = 10, leftIndex = 10));
        gPane.setHgap(2);
        gPane.setVgap(2);
        gPane.add(fibSlider, colIndex = 1, rowIndex = 3);
        gPane.add(indexLabel, colIndex = 1, rowIndex = 5);
        gPane.add(tfIndex, colIndex = 2, rowIndex = 5);
        gPane.add(butCalcFib, colIndex = 1, rowIndex = 6);
        gPane.add(fibNumLabel, colIndex = 1, rowIndex = 7);
        gPane.add(tfFibNum, colIndex = 2, rowIndex = 7);

        return gPane;
    }

    public Main() {
        tfIndex = new TextField();
        tfFibNum = new TextField();
    }

    public static void ComputeFibonacci() {
        double index = fibSlider.getValue();
        // Find and display the Fibonacci number
        fib((long) index);
    }

    /**
     * The method for finding the Fibonacci number
     */
    public static long fib(long index) {
        if (index == 0) // Base case
        {
            return 0;
        } else if (index == 1) // Base case 
        {
            return 1;
        } else // Reduction and recursive calls 
        {
            return fib(index - 1) + fib(index - 2);
        }
    }

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

Answer 1

您可以通过让滑块的侦听器更新两个索引和结果字段来大大简化您的代码。那么你只需要一个滑块监听器，不需要按钮。

    fibSlider.valueProperty().addListener(sl -> {
        long value = (long) fibSlider.getValue();
        tfIndex.setText(Long.toString(value));
        tfFibNum.setText(Long.toString(fib(value)));
    });

另见Q&A 关于观察者模式。在下面的变体中，

• GridPane 允许滑块跨越两列。

• 调用滑块的setBlockIncrement() 方法可让您使用箭头键更改滑块。

• 在滑块的InvalidationListener 中，您可以引用滑块的DoubleProperty 值，而不是引用封闭类的fibSlider 字段。

经测试：

import javafx.application.Application;
import javafx.beans.property.DoubleProperty;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

/** @see https://stackoverflow.com/a/37068554/230513 */
public class Main extends Application {

    private final Slider fibSlider = new Slider(0, 10, 0);
    private final Label indexLabel = new Label("Index: ");
    private final Label fibNumLabel = new Label("Fibonacci #: ");
    private final TextField tfIndex = new TextField("0");
    private final TextField tfFibNum = new TextField("0");

    @Override
    public void start(Stage primaryStage) {
        fibSlider.setMajorTickUnit(1);
        fibSlider.setMinorTickCount(0);
        fibSlider.setShowTickLabels(true);
        fibSlider.setShowTickMarks(true);
        fibSlider.setSnapToTicks(true);
        fibSlider.setBlockIncrement(1.0);
        fibSlider.valueProperty().addListener(sl -> {
            long value = ((DoubleProperty) sl).longValue();
            tfIndex.setText(Long.toString(value));
            tfFibNum.setText(Long.toString(fib(value)));
        });

        GridPane mainGPane = buildGPane();
        Scene mainScene = new Scene(mainGPane);
        primaryStage.setTitle("Fibonacci Calculator");
        primaryStage.setScene(mainScene);
        primaryStage.show();
    }

    private GridPane buildGPane() {
        GridPane gPane = new GridPane();
        gPane.setAlignment(Pos.CENTER);
        gPane.setPadding(new Insets(10, 10, 10, 10));
        gPane.setHgap(10);
        gPane.setVgap(10);
        gPane.add(fibSlider, 0, 0, 2, 1);
        gPane.add(indexLabel, 0, 1);
        gPane.add(tfIndex, 1, 1);
        gPane.add(fibNumLabel, 0, 2);
        gPane.add(tfFibNum, 1, 2);
        return gPane;
    }

    /**
     * The method for finding the Fibonacci number
     */
    public long fib(long index) {
        if (index == 0) {
            return 0;
        } else if (index == 1) {
            return 1;
        } else {
            return fib(index - 1) + fib(index - 2);
        }
    }

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