插入小數點Java計算器GUI

Question

我一直想弄清楚如何在要構建的非常簡單的計算器gui中添加小數位函數。 我對makeDecimalButton函數的當前實現在運行時引發錯誤。 我不應該將小數解析為雙精度嗎？ 也許我應該使用BigDecimal？ 任何幫助表示贊賞。

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.*;
import javafx.stage.Stage;
import javafx.stage.StageStyle;

import java.util.HashMap;
import java.util.Map;

public class Calculator extends Application {
    private static final String[][] template = { 
            { "7", "8", "9", "/" }, 
            { "4", "5", "6", "*" }, 
            { "1", "2", "3", "-" },
            { "0", "C", "=", "+", "." } };

    private final Map<String, Button> accelerators = new HashMap<>();

    private DoubleProperty stackValue = new SimpleDoubleProperty();
    private DoubleProperty value = new SimpleDoubleProperty();

    private enum Operation {
        NOOP, ADD, SUBTRACT, MULTIPLY, DIVIDE
    }

    private Operation curOp = Operation.NOOP;
    private Operation stackOp = Operation.NOOP;

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

    @Override
    public void start(Stage stage) {
        final TextField screen = createScreen();
        final TilePane buttons = createButtons();

        stage.setTitle("Calculator");
        stage.initStyle(StageStyle.UTILITY);
        stage.setResizable(false);
        stage.setScene(new Scene(createLayout(screen, buttons)));
        stage.show();
    }

    private VBox createLayout(TextField screen, TilePane buttons) {
        final VBox layout = new VBox(20);
        layout.setAlignment(Pos.CENTER);
        layout.setStyle("-fx-background-color: black; -fx-padding: 20; -fx-font-size: 20;");
        layout.getChildren().setAll(screen, buttons);
        handleAccelerators(layout);
        screen.prefWidthProperty().bind(buttons.widthProperty());
        return layout;
    }

    private void handleAccelerators(VBox layout) {
        layout.addEventFilter(KeyEvent.KEY_PRESSED, new EventHandler<KeyEvent>() {
            @Override
            public void handle(KeyEvent keyEvent) {
                Button activated = accelerators.get(keyEvent.getText());
                if (activated != null) {
                    activated.fire();
                }
            }
        });
    }

    private TextField createScreen() {
        final TextField screen = new TextField();
        screen.setStyle("-fx-background-color: white;");
        screen.setAlignment(Pos.CENTER_RIGHT);
        screen.setEditable(false);
        screen.textProperty().bind(Bindings.format("%f", value));
        return screen;
    }

    private TilePane createButtons() {
        TilePane buttons = new TilePane();
        buttons.setVgap(7);
        buttons.setHgap(7);
        buttons.setPrefColumns(template[0].length);
        for (String[] r : template) {
            for (String s : r) {
                buttons.getChildren().add(createButton(s));
            }
        }
        return buttons;
    }

    private Button createButton(final String s) {
        Button button = makeStandardButton(s);

        if (s.matches("[0-9]")) {
            makeNumericButton(s, button);
        } else {
            final ObjectProperty<Operation> triggerOp = determineOperand(s);
            if (triggerOp.get() != Operation.NOOP) {
                makeOperandButton(button, triggerOp);
            } else if ("C".equals(s)) {
                makeClearButton(button);
            } else if ("=".equals(s)) {
                makeEqualsButton(button);
            } else if (".".equals(s)) {
                makeDecimalButton(button);
            }
        }

        return button;
    }

    private void makeDecimalButton(Button button) {
        button.setStyle("-fx-base: mistyrose;");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                value.set(value.get() + Double.parseDouble("."));
            }
        }); 
    }

    private ObjectProperty<Operation> determineOperand(String s) {
        final ObjectProperty<Operation> triggerOp = new SimpleObjectProperty<>(Operation.NOOP);
        switch (s) {
        case "+":
            triggerOp.set(Operation.ADD);
            break;
        case "-":
            triggerOp.set(Operation.SUBTRACT);
            break;
        case "*":
            triggerOp.set(Operation.MULTIPLY);
            break;
        case "/":
            triggerOp.set(Operation.DIVIDE);
            break;
        }
        return triggerOp;
    }

    private void makeOperandButton(Button button, final ObjectProperty<Operation> triggerOp) {
        button.setStyle("-fx-base: lightgray;");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                curOp = triggerOp.get();
            }
        });
    }

    private Button makeStandardButton(String s) {
        Button button = new Button(s);
        button.setStyle("-fx-base: beige;");
        accelerators.put(s, button);
        button.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        return button;
    }

    private void makeNumericButton(final String s, Button button) {
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                if (curOp == Operation.NOOP) {
                    value.set(value.get() * 10 + Integer.parseInt(s));
                } else {
                    stackValue.set(value.get());
                    value.set(Integer.parseInt(s));
                    stackOp = curOp;
                    curOp = Operation.NOOP;
                }
            }
        });
    }

    private void makeClearButton(Button button) {
        button.setStyle("-fx-base: mistyrose;");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                value.set(0);
            }
        });
    }

    private void makeEqualsButton(Button button) {
        button.setStyle("-fx-base: ghostwhite;");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @SuppressWarnings("incomplete-switch")
            @Override
            public void handle(ActionEvent actionEvent) {
                switch (stackOp) {
                case ADD:
                    value.set(stackValue.get() + value.get());
                    break;
                case SUBTRACT:
                    value.set(stackValue.get() - value.get());
                    break;
                case MULTIPLY:
                    value.set(stackValue.get() * value.get());
                    break;
                case DIVIDE:
                    value.set(stackValue.get() / value.get());
                    break;
                }
            }
        });
    }
}

Answer 1

從文檔中：

parseDouble(String s)
Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double.

因此您正在嘗試從字符串“。”中解析一個雙精度型。 這不是有效的十進制數字。