Java图形界面 简易BMI计算器怎样设计算法

Question

老师出差去了 布置作业做一个简易BMI计算器
写了半天才写出一个图形界面
不知道怎样实现键盘录入身高、体重，点击评估按钮得到BMI和结果（结果输出的是胖，瘦，正常三种情况）
代码、界面如下:

Answer 1

你的核心问题是如何对按钮进行响应，需要看下ActionListener的相关方法。

    public class BMI extends JFrame{

    private JLabel lblHeight;
    private JLabel lblWeight;
    private JLabel lblBMI;
    private JLabel lblResult;

    private JButton btnRun;
    private JPanel pnlMain;
    private JTextField txtHeight;
    private JTextField txtWeight;
    private JTextField txtBMI;
    private JTextField txtResult;
    DecimalFormat dformat = new DecimalFormat("#.00");
    public BMI(){
        lblHeight = new JLabel("身高(米/m)");
        txtHeight = new JTextField(10);
        lblWeight = new JLabel("体重(千克/kg)");
        txtWeight = new JTextField(10);
        lblBMI = new JLabel("健康值(BMI)");
        txtBMI = new JTextField(10);
        lblResult = new JLabel("结果");
        txtResult = new JTextField(10);
        btnRun = new JButton("评估");
        pnlMain = new JPanel();
        pnlMain.setLayout(null);
        lblHeight.setBounds(100, 50, 80, 25);
        txtHeight.setBounds(200, 50, 100, 25);
        lblWeight.setBounds(100, 80, 80, 25);
        txtWeight.setBounds(200, 80, 100, 25);
        lblBMI.setBounds(100, 110, 80, 25);
        txtBMI.setBounds(200, 110, 100, 25);
        lblResult.setBounds(100, 170, 80, 25);
        txtResult.setBounds(200, 170, 100, 25);
        btnRun.setBounds(150, 140, 80, 25);

        pnlMain.add(lblHeight);
        pnlMain.add(txtHeight);
        pnlMain.add(lblWeight);
        pnlMain.add(txtWeight);
        pnlMain.add(lblBMI);
        pnlMain.add(txtBMI);
        pnlMain.add(lblResult);
        pnlMain.add(txtResult);
        pnlMain.add(btnRun);
        this.setContentPane(pnlMain);
        setSize(400,300);
        setTitle("健康评估");
        setVisible(true);
        setResizable(false);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setLocationRelativeTo(null);

        btnRun.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                // TODO Auto-generated method stub
                if( txtWeight.getText() == null){
                    JOptionPane.showMessageDialog(null, "身高为空，请输入一个正值身高！");
                    return;
                }
                if( txtHeight.getText() == null){
                    JOptionPane.showMessageDialog(null, "体重为空，请输入一个正值体重！");
                    return; 
                }
                double weight = Double.valueOf(txtWeight.getText());
                if(weight <= 0 ){
                    JOptionPane.showMessageDialog(null, "体重为0，请输入一个正值体重。");
                    return;
                }
                double height = Double.valueOf(txtHeight.getText());
                if(height <= 0 ){
                    JOptionPane.showMessageDialog(null, "身高为0，请输入一个正值身高。");
                    return;
                }
                double bmi = weight/height/height;
                txtBMI.setText(dformat.format(bmi));
                txtResult.setText(getResult(bmi));
            }

        });
    }
    private String getResult(double bmi) {
        // TODO Auto-generated method stub
        if(bmi < 18.5){
            return "瘦";
        }else if(bmi>=18.5 && bmi < 24){
            return "正常";
        }else{
            return "胖";
        }
    }

    public static void main(String[] args) {
        new BMI();
    }
}