Question

我正在为学校制定一个代码，你可以选择一种贷款类型，然后它会花掉你所欠的金额，并告诉你需要多长时间来偿还贷款。我使用了一些基本的JTextField来允许用户输入，然后使用.getText（）来检索信息。但是，当我使用该字段时，它会在我的控制台中返回nullnull。我一直试图解决这个问题并且已经改变了很多代码，而且我对编码很新，所以可能有点难以理解。如果有人可以帮我解决为什么它会返回null，我会感到沮丧吗？

CODE HERE

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Scanner;
public class Loan1 extends JFrame  implements ActionListener
 {
String paymentTotal, total;
double a;
double b;
double g;
String Total;
FlowLayout flowLayout = new FlowLayout();
private JButton bl = new JButton("Business Loan");
private JButton pl = new JButton("Personal Loan");
private JButton cl = new JButton("Create a Loan");
private JButton submit = new JButton("Submit");
TextField textField = new TextField(20);


JLabel thing = new JLabel("How long were you looking to payoff the loan?");
JLabel thing2 = new JLabel("you will have to pay " + g + " $ a month");


    public Loan1(){
        setLayout(flowLayout);
        add("Business Loan",bl);
        add("Personal Loan",pl);
        add("Create a Loan",cl);
        bl.addActionListener(this);
        pl.addActionListener(this);
        cl.addActionListener(this);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void actionPerformed(ActionEvent e)
    {
        if (e.getSource() == bl || e.getSource() == pl 
|| e.getSource() ==   cl)

            payment();
        if (e.getSource() == submit) {
            Submit();
        }
        repaint();
        //b = new Double(Total);
        System.out.print(Total);
        System.out.print(paymentTotal);
        add(thing);
        TextField textField = new TextField(20);
        String text = textField.getText();
        add(textField);
        remove(bl);
        remove(cl);
        remove(pl);

        if(text.equals("1")){
            a = 1;
            //g = paymentTotal/a *12
            add(thing2);
        }
        if(text.equals("2")){
            a = 2;
            //g = paymentTotal/a *12
            add(thing2);
        }
        if(text.equals("3")){
            a = 3;
            //g = paymentTotal/a *12
            add(thing2);
        }
        if(text.equals("4")){
            a = 1;
            //g = paymentTotal/a *12
            add(thing2);
        }
        if(text.equals("5")){
            a = 1;
            //g = paymentTotal/a *12
            add(thing2);
        }
        }
    public static void main(String[] args)
    {
        Loan1 JBL = new Loan1();
        JBL.setSize(250,250);
        JBL.setVisible(true);
    }


    public void payment() {
        JLabel thing1 = new JLabel("How much money
   were you looking to get a loan for?");
        add(thing1);
        add(textField);
        add(submit);
    }
    public void Submit (){
        String Total = textField.getText();
        paymentTotal = Total;
        System.out.print(Total);
        remove(textField);

    }

  }

Answer 1

首先：在您的方法付款（）中，您忘了：

ID  | Name | Friend  | Enemy   | Alien   | Monster |
35  | John | Friend  | -blank- | -blank- | Monster |
42  | Eric | -blank- | -blank- | -blank- | -blank- |

为什么你没有为每个按钮指定自己的actionPerformed？

返回空值的文本字段

1 个答案: