How to get text from JTextField? [duplicate]

Question

This question already has answers here:

Retrieving JTextField Contents Like Scanner (2 answers)

Closed 9 years ago.

I'm trying to understand the Scanner function, but I can't seem to understand it.

I'm making a program to calculate the BMI (body mass index) and it's practically done, except that I can't make the calculation! Everything works fine except for when I click the "ok" button.

Had to take away my code so my collegues won't copy my code, like they've made in the past, will be posting again after friday.

Answer 1

first thing there is no poblem with Scanner things and its not required when we use GUI.

its useful only for console input/output.

so when you get text it will be in string format so parse it to double like

String val = txt1.getText();
double valueDouble = Double.parseDouble(val);

and handle the parse exception using try/catch

so replace the piece of code below

 Scanner dado1 = new Scanner(txt1.getText());
            System.out.println(dado1);
                if(dado1.hasNextDouble()){
                    tamanho = dado1.nextDouble();
                }
            Scanner dado2 = new Scanner(txt2.getText());
                if(dado2.hasNextDouble()){
                    peso = dado2.nextDouble();
                }

to

String t1 = txt1.getText();
if(!"".equals(t1))
tamanho = Double.parseDouble(t1);


String t2 = txt2.getText();
if(!"".equals(t2))
peso = Double.parseDouble(t2);

i tried to run your program but i got the exception saying -> container does not have parent attribute.

so what i did is i have added a parent container inside your ok button action listener

and it works well.

container to be added is

final JDesktopPane desk = new JDesktopPane();
                    setContentPane(desk);

to your

JOptionPane.showInternalMessageDialog(desk,"Seu IMC é:"+ (result/ peso));

but you have passed null as the first argement.

so it should become like below

   ok.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent evt){
            String t1 = txt1.getText();
            if(!"".equals(t1))
            tamanho = Double.parseDouble(t1);


            String t2 = txt2.getText();
            if(!"".equals(t2))
            peso = Double.parseDouble(t2);
              result = tamanho*tamanho;
            if (ok != null){
                System.out.println(result);
                System.out.println(peso);
                final JDesktopPane desk = new JDesktopPane();
                setContentPane(desk);
                JOptionPane.showInternalMessageDialog(desk,"Seu IMC é:"+ (result/ peso));
            }
        }
    });

Answer 2

you may simply parse instead of Scanner:

tamanho = Double.parseDouble(txt1.getText());