如何從同一文本字段中獲得兩個值？

Question

我是GUI的新手，正在嘗試在JFrame中創建一個計算器，但是每當執行加法運算時，它都說該字符串為空。如果刪除了"jTextField1.setText("");" 部分可以正常工作，但先前的文本仍在文本字段中。 有沒有辦法創建文本字段的另一個實例或類似的東西來容納第二個字符串？

 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

我認為您需要此代碼。

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");
}

}