Question

我浏览了其他一些问题，但没有发现我的确切问题。这是问题所在，我有这个Java GUI BMI计算器，并且一切正常，除了我得到了BMI的无穷大。奇怪的是，当我将输出语句包括到BMI中时，它在控制台上的显示就很好。控制台和GUI计算器使用的是相同的hp.getBMI（），因此为什么一个要获得正确的输出而另一个要显示无穷大。如果我的代码草率，请原谅我，这是我的第一个Java程序，我还没有完成编辑。提前致谢。

public class HealthProfile 
{
    private int age;
    private double height, heightFt, heightIn, weight, BMI, maxHR;
    private String name, category;

    //parameterized constructor
    public HealthProfile(String name, int age, double heightFt, double heightIn, double weight)
    {
        this.name = name;
        this.age = age;
        this.heightFt = heightFt;
        this.heightIn = heightIn;
        this.weight = weight;

    }
    //default constructor
    public HealthProfile()
    {
        this("",0,0,0,0);
    }

    public double getHeight()
    {
        height = heightIn + heightFt * 12;  
        return height;
    }
    public double getBMI()
    {
        BMI = weight * 703 / (height * height);
        return BMI;
    }

    public double getMaxHR()
    {
        maxHR = 220 - age;
        return maxHR;
    }
    public String getCategory()
    {
        if (BMI < 18.5)
            category = "Underweight";
        else if (BMI >= 18.5 && BMI <= 24.9)
            category = "Normal";
        else if (BMI >= 25 && BMI <= 29.9)
            category = "Overweight";
        else
            category = "Obese";
        return category;
    }

}

HealthProfile_GUI.java：

public class HealthProfile_GUI extends JFrame implements ActionListener 
{
        //Private textfields for name, age, height (feet), height (inches),
        //weight, BMI, category, and max heart rate
        private JTextField txtName = new JTextField(25);
        private JTextField txtAge = new JTextField(3);
        ...

        //Private JLabels for those textfields
        private JLabel lblName = new JLabel("Name");
        ...

        private JButton btnCalc = new JButton("Calcualte BMI");
        private JButton btnClear = new JButton("Clear");
        private HealthProfile hp;

        public HealthProfile_GUI()
        {
            setTitle("Health Profile");
            setSize(400,500);
            setVisible(true);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            Container c = getContentPane();
            c.setLayout(new GridLayout(9,2,10,10));

            c.add(lblName);
            c.add(txtName);
            ...and add all the other text fields and labels

            btnCalc.addActionListener(this);
            btnClear.addActionListener(this);
        }

        @Override
        public void actionPerformed(ActionEvent ae)
        {
            boolean notEmpty = true;
            if(hp == null)
            {
                hp = new HealthProfile();
            }
            if (ae.getSource() == btnCalc) 
            {
                System.out.println("Calculating BMI");

                if(txtName.getText().equals("") || txtName.getText().isEmpty()) 
                {
                    JOptionPane.showMessageDialog(null,"Name is required");
                    notEmpty = false;
                }
                if(txtAge.getText().equals("") || txtAge.getText().isEmpty())
                {
                    JOptionPane.showMessageDialog(null,"Age is required");
                    notEmpty = false;
                }
                if(txtHeightFt.getText().equals("") || txtHeightFt.getText().isEmpty()) 
                {
                    JOptionPane.showMessageDialog(null,  "Height (Feet) is required");
                    notEmpty = false;
                }
                if(txtHeightIn.getText().equals("") || txtHeightIn.getText().isEmpty()) 
                {
                    JOptionPane.showMessageDialog(null,  "Height (Inches) is required");
                    notEmpty = false;
                }
                if(txtWeight.getText().equals("") || txtWeight.getText().isEmpty()) 
                {
                    JOptionPane.showMessageDialog(null,  "Weight is required");
                    notEmpty = false;
                }
                if (notEmpty == true) 
                {
                    hp.setName(txtName.getText());
                    hp.setAge(Integer.parseInt(txtAge.getText()));
                    hp.setHeightFt(Double.parseDouble(txtHeightFt.getText()));
                    hp.setHeightIn(Double.parseDouble(txtHeightIn.getText()));
                    hp.setWeight(Double.parseDouble(txtWeight.getText()));
                    txtBMI.setText(String.format("%.2f", hp.getBMI()));
                    txtCat.setText(hp.getCategory());
                    txtMaxHR.setText(String.format("%.0f", hp.getMaxHR()));
                    System.out.println(hp.getWeight());
                    System.out.println(hp.getHeight());
                    System.out.println(hp.getHeightFt());
                    System.out.println(hp.getHeightIn());
                    System.out.println(hp.getBMI());
                }
            }
            else if(ae.getSource() == btnClear)
            {
                txtName.setText("");
                txtAge.setText("");
                txtHeightFt.setText("");
                txtHeightIn.setText("");
                txtWeight.setText("");
                txtBMI.setText("");
                txtCat.setText("");
                txtMaxHR.setText("");
            }                       
        }                   
}

仅运行GUI的主类

public class HealthProfileMain {

    public static void main(String[] args) 
    {
        HealthProfile_GUI hp = new HealthProfile_GUI();
    }
}

Answer 1

方法getBMI()不计算高度：它仅由getHeight()设置，在第一次调用getBMI()之前不会被调用。

也就是说，您的事件侦听器正确读取了heightFt和heightIn的值，但是height仍然为零。最好也更新height，即您阅读heightFt和heightIn的每个时机。

因此，第一次调用getBMI()会除以零（因此无穷大，因为这在Java浮点数中不是错误），而第二次调用getBMI()则得到正确的{ {1}}，因此是正确的结果。

Answer 2

第一次调用getBMI（）时，未设置高度。但是在第二个调用之前，您调用了getHeight（），它为height设置了正确的值。

Java GUI BMI计算器将Infinity作为BMI返回

2 个答案: