为什么java不从GUI中获取数字？

-4

我创建了一个贷款计算器。但它没有计算价值。请你帮我找到出了什么问题。为什么java不从GUI中获取数字？

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



public void initUIPanel() { 
    jf = new JFrame(); 
    jf.setTitle("Mortgage Calculator"); 
    jf.setLocation(100, 200); 
    jf.setSize(530, 740); 
    jf.setVisible(true); 
    jf.setResizable(false); 


    GridBagLayout gbl = new GridBagLayout(); 
    GridBagConstraints gbc = new GridBagConstraints(); 
    JPanel pane = new JPanel(gbl); 
    JPanel pane1 = new JPanel(gbl); 
    JPanel pane2 = new JPanel(gbl); 
    gbc.anchor = GridBagConstraints.WEST; 



    gbc.weightx = 1.0; 
    gbc.insets = new Insets(30, 3, 3, 3); 
    loanAmount = new JTextField(12); 
    gbc.gridx = 1; 
    gbc.gridy = 0; 
    gbc.fill = GridBagConstraints.BOTH; 
    gbl.setConstraints(loanAmount, gbc); 
    pane.add(loanAmount); 



    loanTerm = new JTextField(15); 
    gbc.weightx = 1.0; 
    gbc.insets = new Insets(20, 3, 3, 3); 
    loanAmount = new JTextField(12); 
    gbc.gridx = 1; 
    gbc.gridy = 1; 
    gbc.fill = GridBagConstraints.BOTH; 
    gbl.setConstraints(loanAmount, gbc); 
    pane.add(loanAmount); 




    gbc.insets = new Insets(30, 0, 3, 0); 
    interestRate = new JTextField(4); 
    gbc.gridx++; 
    gbc.gridy = 3; 
    gbc.fill = GridBagConstraints.BOTH; 
    gbl.setConstraints(interestRate, gbc); 
    pane2.add(interestRate); 


    b1 = new JButton("Calculate"); 
    b1.setPreferredSize(new Dimension(5, 25)); 
    gbc.gridx = 0; 
    gbc.gridy = 5; 
    gbc.insets = new Insets(20, 30, 0, 30); 
    b1.addActionListener(this); 
    gbl.setConstraints(b1, gbc); 
    pane2.add(b1); 




    jf.add(pane, BorderLayout.NORTH); 
    jf.add(pane2, BorderLayout.SOUTH); 
    jf.setVisible(true); 
    jf.pack(); 


} 

public void actionPerformed(ActionEvent e) { 


    double amt, rate, pay; 
    int time; 
    String name; 

    if (e.getSource() == b1) { 
     amt = Double.parseDouble(loanAmount.getText()); 
     rate = Double.parseDouble(interestRate.getText()); 
     time = Integer.parseInt(loanTerm.getText()); 


     System.out.println(amt); 
     System.out.println(rate); 
     System.out.println(time); 


    } else { 
     jf.dispose(); 
    } 
} 




public static void main(String[] args) { 
    // TODO Auto-generated method stub 
    MortgageCalculator mc = new MortgageCalculator(); 
    mc.initUIPanel(); 



} 

}

我有

我有一个计算不同类不同的类，但ATLEAST未服用的价值，甚至在同一个班级。当我输入任何值时，它显示异常错误。我编辑了代码，缩短了它们。我得到的错误

异常在线程“AWT-EventQueue-0”java.lang.NumberFormatException：对于输入字符串：“” 即使当我把值放入textAreas。

来源

2013-06-02 Shasi

什么是例外？ –

这是太多的代码。将其分解为[SSCCE]（http://sscce.org），并且不要忘记发布确切的错误消息... – jlordo

线程“AWT-EventQueue-0”中的异常java.lang.NumberFormatException：For输入字符串：“” – Shasi

您永远不会将JTextFieldloanTerm添加到JPanelpane，因此它仍保留其默认值为空的String值。发生ActionListener时，空的String会导致NumberFormatException。

添加JTextField到容器：

pane.add(loanTerm);

来源

2013-06-02 14:35:22 Reimeus

为什么java不从GUI中获取数字？

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