请写一个JAVAfx的简易计算器

当然可以！下面是一个简单的JavaFX计算器的示例代码：

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

public class SimpleCalculator extends Application {
    
    private TextField display;

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Simple Calculator");
        
        GridPane grid = new GridPane();
        grid.setPadding(new Insets(10));
        grid.setHgap(5);
        grid.setVgap(5);
        
        display = new TextField();
        display.setPrefWidth(200);
        display.setEditable(false);
        grid.add(display, 0, 0, 4, 1);
        
        String[] buttons = {
            "7", "8", "9", "/",
            "4", "5", "6", "*",
            "1", "2", "3", "-",
            "0", ".", "=", "+"
        };
        
        int row = 1;
        int col = 0;
        
        for (String button : buttons) {
            Button btn = new Button(button);
            btn.setPrefSize(50, 50);
            btn.setOnAction(e -> handleButtonClick(button));
            
            grid.add(btn, col, row);
            
            col++;
            if (col > 3) {
                col = 0;
                row++;
            }
        }
        
        Scene scene = new Scene(grid);
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    
    private void handleButtonClick(String button) {
        if (button.equals("=")) {
            evaluateExpression();
        } else {
            display.setText(display.getText() + button);
        }
    }
    
    private void evaluateExpression() {
        String expression = display.getText();
        
        try {
            double result = Calculator.evaluate(expression);
            display.setText(Double.toString(result));
        } catch (Exception e) {
            display.setText("Error");
        }
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

注意：这只是一个简单的示例，实际上并没有实现完整的计算功能。你需要自己实现 Calculator 类，用于计算表达式的结果。你可以根据需要进行扩展和修改。希望对你有所帮助！