萌新求助

萌新寫了給小計算器 想問一下為什么我按C按鈕后 會在文本框內生成一個C字符呢？

以下是全部的代碼
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/**
 * @author 86176
 */
public class Main implements ActionListener {

    static boolean hasPoint = false;
    static String preKey;
    private static double result;
    JTextField tf;
    JTextField tf1;
    JButton bt;
    String[] buttonText = {"7", "8", "9", "/",
                           "4", "5", "6", "*",
                           "1", "2", "3", "-",
                           "0", ".", "=", "+",};
    String strA = "";
    String strB = "";
    String strC = "";

    char operator = '~';

    public static void main(String[] args){
        preKey = "";
        hasPoint = false;
        Main app = new Main();
        app.go();
    }

    void go() {


        //整體的框架
        JFrame frame = new JFrame("Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //顯示計算結果的方框
        tf = new JTextField();
        tf1 = new JTextField(20);
        tf.setPreferredSize(new Dimension(400, 60));


        bt = new JButton();

        JPanel p1 =new JPanel();
        JButton b1 = new JButton("C");
        b1.addActionListener(this);
        p1.add(tf1);
        p1.add(b1);

        // 添加方框和按鈕到框架
        frame.getContentPane().add(tf, BorderLayout.NORTH);
        frame.getContentPane().add(bt, BorderLayout.CENTER);
        frame.getContentPane().add(p1, BorderLayout.SOUTH);

        //放按鈕的方框
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(4, 4));

        for (int i = 0; i < 16; i++){
            JButton bt = new JButton(buttonText[i]);
            p.add(bt);
            bt.addActionListener(this);
        }
        frame.getContentPane().add(p, BorderLayout.CENTER);


        //框架大小
        frame.setSize(300, 400);
        frame.setVisible(true);
    }
    @Override
    public void actionPerformed(ActionEvent e) {
  double secondOperand = 0.0;
        String whichButton = "";

        try {
            whichButton = e.getActionCommand().trim();
            System.out.println("Action now " + whichButton.toString());
            if ("C".equals(whichButton)){
                tf.setText("");
                tf1.setText("");
                hasPoint = false;
            }
            if (".".equals(whichButton)){
                if (hasPoint){
                    tf1.setText("操作非法，已經有小數點了");
                }else {
                    tf.setText(tf.getText() + ".");
                    hasPoint = true;
                }
            }else {
                if ("1234567890".contains(whichButton)){
                    for (int i = 0; i <= 9; i++){
                        if (Integer.parseInt(whichButton) == i){
                            tf.setText(tf.getText() + Integer.toString(i));
                        }
                    }
                }
                if (!"".equals(tf.getText())){
                    secondOperand = Double.valueOf(tf.getText()).doubleValue();
                }
            }
            if ("=+-*/".contains(whichButton)){
                tf.setText("");
                hasPoint = false;
                switch (preKey){
                    case "+":
                        result += secondOperand;
                        break;
                    case "-":
                        result -=  secondOperand;
                        break;
                    case "*":
                        result *= secondOperand;

                        break;
                    case "/":
                        result /= secondOperand;
                        break;
                    default:
                        result = secondOperand;
                        tf.setText("");
                }
                if ("=".equals(whichButton)){
                    tf.setText(String.valueOf(result));
                    if (tf.getText().contains(".")){
                        hasPoint = true;
                    }
                }
                preKey = whichButton;
            }
            tf1.setText(tf1.getText() + whichButton.toString());
        } catch (Exception e1) {
            tf1.setText("操作非法" + e1.toString());
            e1.printStackTrace();
        }
    }
}

uj5u.com熱心網友回復：

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uj5u.com熱心網友回復：

            if ("C".equals(whichButton)){
                tf.setText("");
                tf1.setText("");
                hasPoint = false;
            // 添加
            return;

            }

這個里面,按 C表示已經結束了, 應該直接回傳,不再向下了.

uj5u.com熱心網友回復：

你要將按鈕系結到這個事件上： actionPerformed

轉載請註明出處，本文鏈接：https://www.uj5u.com/houduan/283245.html

標籤：Java相關

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