java - 如何从同一文本字段获取两个值？

Question

我是 GUI 新手，尝试在 JFrame 中制作计算器，但每当我执行加法操作时，它都会说字符串为空。如果我删除 "jTextField1.setText("");" 部分，它工作正常，但之前的文本仍然在文本字段中。有没有办法创建文本字段的另一个实例或类似的东西来容纳第二个字符串？

 private void jButton10ActionPerformed(java.awt.event.ActionEvent evt) {                                          
        a=Float.parseFloat(jTextField1.getText());
         jTextField1.setText("");
        b=Float.parseFloat(jTextField1.getText());
        res=a+b; 

    }  

Answer 1

我认为您需要此代码。

enter code here

import java.awt.*;
import javax.swing.*;

class Calculation_ActionEvent extends JFrame implements ActionListener {
JFrame f;
JLabel l;
JTextField tf1, tf3;
JButton b1, b2, b3, b4, b5, b6;

Calculation_ActionEvent(String s) {
    f = new JFrame(s);
    f.setLayout(null);
    l = new JLabel("Enter two numbers : ");
    tf1 = new JTextField();
    // tf2 = new JTextField();
    tf3 = new JTextField();
    b1 = new JButton("+");
    b2 = new JButton("-");
    b3 = new JButton("*");
    b4 = new JButton("/");
    b5 = new JButton("equals");
    b6 = new JButton("C");
    f.add(l);
    f.add(tf1);
    f.add(tf3);
    f.add(b1);
    f.add(b2);
    f.add(b3);
    f.add(b4);
    f.add(b5);
    f.add(b6);
    tf1.setBounds(160, 100, 250, 30);
    // tf2.setBounds(320,100,50,30);
    tf3.setBounds(250, 420, 50, 30);
    b1.setBounds(250, 180, 50, 30);
    b2.setBounds(350, 260, 50, 30);
    b3.setBounds(150, 260, 50, 30);
    b4.setBounds(250, 340, 50, 30);
    b5.setBounds(230, 260, 90, 30);
    b6.setBounds(420, 100, 50, 30);
    b1.addActionListener(this);
    b2.addActionListener(this);
    b3.addActionListener(this);
    b4.addActionListener(this);
    b5.addActionListener(this);
    b6.addActionListener(this);
    f.setSize(550, 550);
    f.setVisible(true);
}

int total = 0;
String lastAction = "";

public void actionPerformed(ActionEvent e) {
    int num = 0;
    try {
        num = Integer.parseInt(tf1.getText());
    } catch(NumberFormatException ex) {}
    String s1 = e.getActionCommand();
    if (s1.equals("C")) {
        tf1.setText("");
        tf3.setText("0");
        tf1.requestFocus();
        total = 0;
    } else if (s1.equals("equals")) {
        tf3.setText(String.valueOf(calc(total, lastAction, num)));
        tf1.setText("");
        tf1.requestFocus();
        total = 0;
    } else {
        total = total==0 ? num : calc(total, lastAction, num);
        tf3.setText(String.valueOf(total));
        tf1.setText("");
        tf1.requestFocus();
        lastAction = s1;
    }
}

private int calc(int num1, String action, int num2) {
    switch (action) {
    case "+":
        return num1 + num2;
    case "-":
        return num1 - num2;
    case "*":
        return num1 * num2;
    case "/":
        return num1 / num2;
    default:
        return num1;
    }
}

public static void main(String... s) {
    new Calculation_ActionEvent("Calculator");
}

}