Problem when holding a button event in Java Swing

Question

I’m having a problem doing an event on a button (using textfield to set values) and calling a method to calculate BMI (I haven’t finished this method yet).

Code: (java screen.)

package calculadoraimc;
import javax.swing.*;
import java.awt.*;
 //evento para button
import java.awt.event.*; //evento para button

public class tela extends JFrame 
{
    private IMC[] i;
    private JLabel lb1,lb2,lb3;
    private JTextField tf1,tf2,tf3;
    private JButton bt1;
    public tela(){
        setTitle("Calculadora IMC");
        setLayout(new FlowLayout());
        setSize(600,600);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        lb1 = new JLabel("Nome");
        tf1 = new JTextField(20);
        lb2 = new JLabel("Peso");
        tf2 = new JTextField(20);
        lb3 = new JLabel("Altura");
        tf3 = new JTextField(20);
        bt1 = new JButton ("Calcular");
        bt1.addActionListener(new ActionListener(){public void actionPerformed (ActionEvent ev){bConf();}});


        add(lb1);
        add(tf1);   
        add(lb2);
        add(tf2);
        add(lb3);
        add(tf3);
        add(bt1);
    }

    public void bConf() {
    i[Integer.parseInt(tf2.getText())].setNome(tf2.getText());// converter string para inteiro e adicionar em cliente e converte string em inteiro e adicionar em Nome
    i[Integer.parseInt(tf1.getText())].setPeso(Double.parseDouble(tf1.getText())); // converter string para inteiro e adicionar em cliente e converte string em inteiro e adicionar em codigo
    tf1.setText(" "); // limpar campos
    tf2.setText(" ");  
    }
}

IMC.java

package calculadoraimc;

public class IMC{
private String nome;
private double altura,peso,imc;

public void setNome(String n){
this.nome=n;
}
public String getNome(){
return this.nome;
}
public void setAltura(double a){
this.altura=a;
}
public double getAltura(){
return this.altura;
}
public void setPeso(double p){
this.peso=p;
}
public double getpeso(){
return this.peso;
}

public void calcularIMC(){
this.imc=this.peso/(this.altura*this.altura);
if (imc < 16.0){

            }
            if (16< imc && imc <16.99){

            }
            if (17<imc && imc <18.49){


            }
            if (18.50< imc && imc < 24.99){

            }
            if(25<imc && imc <29.99){

            }
            if(30<imc && imc <34.99){

            }
            if(35<imc && imc <39.99){

            }
            if(imc>=40){

            }
}


}

main:

package calculadoraimc;

import java.util.Scanner;

public class programa {
 public static void main(String[] args){
  tela t = new tela();
  IMC i = new IMC();
  t.setVisible(true);

}
}   

Answer 1

If the goal is to pass the captured values in the text fields by clicking the button, there is no need to create an array of type IMC. I would suggest that you create a constructor that receives the necessary values for the calculation, more or less in this way:

public class IMC {

//seus campos...

    public IMC(String nome, double peso, double altura) {

        this.nome = nome;
        this.altura = altura;
        this.peso = peso;

    }

//restante da classe...

}

And instead of starting in main, which is also completely unnecessary since the scope of the IMC class does not need to be part of this, start as class field Tela:

public class Tela {

//...
private IMC imc;
//...

}

and stand inside the button event, passing the values:

bt1.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ev) {
        String nome = tf1.getText();
        double peso = Double.parseDouble(tf2.getText());
        double altura = Double.parseDouble(tf3.getText()); 

        this.imc = new IMC(nome, peso, altura);

        tf1.setText(" ");
        tf2.setText(" ");
    }
});

Then just set where the result will appear on your screen and invoke the method you calculate.

However, your code has a lot of problems worth highlighting below:

• you are not dispatching your application to the Event-Dispatch-thread recommend you read Why the main method should dispatch the creation of the GUI to the EDT in a swing application? and fix your code.

• your class does not agree with the java convention, where class names should always start with uppercase letter.

• Most of your field variables have names that don’t make any sense, which makes your code unreadable. Variable names should tell you what it’s for, and not have generic names that make it difficult to identify. The same goes for method names, they must say what the method does or what it’s for.

It is essential to follow these tips in order to improve your codes and make them more readable.