java - 我可以从 javaFX 中的 setOnAction 参数调用另一个类吗？

Question

我是一个初级程序员，我学了足够多的 java，现在我的目标是使用 JavaFX 为 gui 创建一个计算器，并尽可能让它成为 oop，这样在实践中，其他人很容易修改程序，我在添加按钮并想对其应用 setOnAction 方法时遇到问题，我想有一个单独的类来处理按钮事件，但我不明白如何使用这个特殊的方法

这是 Gui 类:

package calculator;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class Gui extends Application {

    InputHandler inputhandler = new InputHandler();

    Button add = new Button();

    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setTitle("HackCalc");


        add.setText("+");
        add.setOnAction(inputhandler);


        StackPane layout = new StackPane();
        layout.getChildren().add(add);

        Scene scene = new Scene(layout, 330, 500);

        primaryStage.setScene(scene);
        primaryStage.show();
    }
}

如您所见，我已经创建了一个 InputHandler 类的实例，我将向您展示并将其传递给 setOnAction 但它从未奏效，我遇到了一个令人沮丧的 NoSuchMethodException 错误。

现在，这是 InputManager 类:

import javafx.event.ActionEvent;
import javafx.event.EventHandler;

public  class InputHandler extends Gui implements EventHandler<ActionEvent>{

    @Override
    public void handle(ActionEvent event) {
        if(event.getSource()== add){
            System.out.println("InputHandler works");
        }
    }
}

Answer 1

首先 InputHandler 扩展 Gui 就设计而言没有意义，因为 "is" 关系 InputHandler 和 Gui/Application.

您最好使用匿名类/lambda 表达式作为事件处理程序，并取消对按钮的检查，但改用不同的事件处理程序。这样你就可以摆脱所有的 if (source == someButton) 检查...

有意义的是将 View 与计算器逻辑分开，使 GUI 独立于计算器逻辑。

示例

public class Calculator {

    private final ObservableList<String> formulaParts = FXCollections.observableArrayList();
    private final ObservableList<String> formulaPartsUnmodifiable = FXCollections.unmodifiableObservableList(formulaParts);
    private final ReadOnlyStringWrapper operandString = new ReadOnlyStringWrapper();
    private Integer operand;
    private Integer previousOperand;
    private IntBinaryOperator operator;
    private boolean operandModifiable = true;

    /** previous input elements as Strings */
    public ObservableList<String> getFormulaParts() {
        return formulaPartsUnmodifiable;
    }

    public final String getOperand() {
        return this.operandString.get();
    }

    /** property contains current input as String */
    public final ReadOnlyStringProperty operandProperty() {
        return this.operandString.getReadOnlyProperty();
    }

    public void addDigit(byte digit) {
        if (operandModifiable) {
            operand = operand == null ? digit : operand * 10 + digit;
            operandString.set(Integer.toString(operand));
        }
    }

    public void addBinaryOperator(IntBinaryOperator operator) {
        if (operand != null) {
            if (previousOperand != null) {
                evaluate();
            }

            previousOperand = operand;
            operand = null;
            operandString.set("");
            formulaParts.setAll(Integer.toString(previousOperand), operator.toString());
            this.operator = operator;
            operandModifiable = true;
        }
    }

    public void evaluate() {
        if (operand != null && operator != null) {
            int result = operator.applyAsInt(previousOperand, operand);
            formulaParts.clear();
            operandString.set(Integer.toString(result));
            operandModifiable = false;
            previousOperand = null;

            operand = result;
        }
    }

}

public class BinaryPlusOperator implements IntBinaryOperator {

    @Override
    public int applyAsInt(int left, int right) {
        return left + right;
    }

    @Override
    public String toString() {
        return "+";
    }

}

public class Gui extends Application {

    private final static IntBinaryOperator PLUS = new BinaryPlusOperator();

    @Override
    public void start(Stage primaryStage) {
        Calculator calc = new Calculator();

        // display parts of formula in ListView
        ListView<String> formulaPartsDisplay = new ListView<>(calc.getFormulaParts());
        formulaPartsDisplay.setMaxHeight(30);
        formulaPartsDisplay.setOrientation(Orientation.HORIZONTAL);

        Text operand = new Text();
        operand.setFont(Font.font(20));

        // display current input in Text
        operand.textProperty().bind(calc.operandProperty());

        VBox display = new VBox(5, formulaPartsDisplay, operand);
        display.setAlignment(Pos.CENTER_RIGHT);
        VBox.setVgrow(display, Priority.NEVER);
        display.setBorder(new Border(new BorderStroke(Color.GREEN, BorderStrokeStyle.SOLID, CornerRadii.EMPTY, new BorderWidths(3))));

        Button plus = new Button("+");
        Button eval = new Button("=");
        Button d1 = new Button("1");

        // event handlers invoke appropriate methods of Calculator
        plus.setOnAction(evt -> calc.addBinaryOperator(PLUS));
        eval.setOnAction(evt -> calc.evaluate());
        d1.setOnAction(evt -> calc.addDigit((byte) 1));

        GridPane buttons = new GridPane();
        buttons.add(d1, 0, 0);
        buttons.addRow(1, plus, eval);

        Scene scene = new Scene(new VBox(display, buttons));

        primaryStage.setScene(scene);
        primaryStage.show();
    }