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Oundroni
Asked: 2020-04-24 09:10:16 +0800 CST 2020-04-24 09:10:16 +0800 CST

Limit the size of a TextField in javaFX

  • 772

I want to limit the number of characters a control supports TextFieldand I have tried this method:

    public static void fijarTamañoMáximo(final TextField campoTexto, final int tamañoMáximo) {
        campoTexto.textProperty().addListener(new ChangeListener<String>() {
            @Override
            public void changed(final ObservableValue<? extends String> ov, final String valorAnterior, final String valorActual) {

                Pattern permitido = Pattern.compile("[A-Za-zÑÇÁÉÍÓÚÀÈÌÒÙÏÜÂÊÎÔÛñçáéíóúàèìòùïüâêîôû]");
                Matcher mpermitido = permitido.matcher(valorActual.substring(valorActual.length() - 1));

                if (mpermitido.find()) {
                    if (campoTexto.getText().length() > tamañoMáximo) {
                        String s = campoTexto.getText().substring(0, tamañoMáximo);
                        campoTexto.setText(s);
                    }
                } else // caracter no permitido, borrarlo
                if (valorActual.length() == 1) {
                    campoTexto.setText(""); // ¿Por qué sale error?
                } else {
                    campoTexto.setText(valorAnterior);
                }
            }
        });
   }

fijarTamañoMáximo(miTextField, 10); // limito a 10 caracteres

I also limit the data type to alphabetic characters. Up to here everything works fine (although I accept suggestions to improve it). The problem is that when the first character is typed as one that is not allowed, for example a number, an error comes out when I put the text of the TextFielda "" with campoTexto.setText("");. The same thing happens if I try to delete the single character from the control and I don't know why.

java

3 Answers

  1. Uses: campoTexto.lengthProperty()

    instead of :

    campoTexto.textProperty()

    and uses the same listener, ChangeListenerto validate the number of characters allowed.

    Example:

    public static void fijarTamanoMaximo(final TextField campoTexto, final int tamanoMaximo) {

         campoTexto.lengthProperty().addListener(new ChangeListener<Number>() {

            @Override
            public void changed(ObservableValue<? extends Number> observable,
                    Number valorAnterior, Number valorActual) {
                if (valorActual.intValue() > valorAnterior.intValue()) {
                    // Revisa que la longitud del texto no sea mayor a la variable definida.
                    if (campoTexto.getText().length() >= tamanoMaximo) {
                        campoTexto.setText(campoTexto.getText().substring(0, tamanoMaximo));
                    }
                }
            }
        });

   }

    In this way we can validate our TextField, CustomTextField, etc, to avoid entering more than a certain number of characters.

    enter image description here

    • 0

  2. The problem that I have found in the previous answers is that if the illegal character is entered at the beginning or in the middle of the string then it does not work and allows the wrong character to be entered. To solve it we can go through all the characters of the new string and check one by one if it meets the filter:

    campoTexto.textProperty().addListener((final ObservableValue<? extends String> ov, final String valorAnterior, final String valorActual) -> {

    if (valorActual.length() > valorAnterior.length()) {

        Pattern permitido = Pattern.compile("[\\d]"); // filtro sólo números
        Matcher mpermitido;

        // recorremos la cadena buscando carácteres no deseados               
        for (int i = 0; i < valorActual.length(); i++) {                  
            mpermitido = permitido.matcher(valorActual.substring(i, i + 1));
            if (!mpermitido.find()) {
                campoTexto.setText(valorAnterior);
                return;
            }
        }
        // controlamos la longitud máxima...            
        if (decimales.getText().length() > longitudMáxima) {
            decimales.setText(decimales.getText().substring(0, longitudMáxima));
        }               
    }
});
    • 0
  3. Best Answer

    The error occurs because when an illegal character is typed being the length of TextField0 in the declaration of the Matcherattempt to assign a substring(-1). On the other hand, when the text "" is assigned to TextFieldit causes an automatic refill of the Listener that returns to encounter the same error from the beginning. The solution is to not apply the Patternif nothing has been added to the TextField:

    public static void fijarTamañoMáximo(final TextField campoTexto, final int tamañoMáximo) {
    campoTexto.textProperty().addListener(new ChangeListener<String>() {

        @Override
        public void changed(final ObservableValue<? extends String> ov, final String valorAnterior, final String valorActual) {

            if (valorActual.length() > valorAnterior.length()) {
                Pattern permitido = Pattern.compile("[A-Za-zÑÇÁÉÍÓÚÀÈÌÒÙÏÜÂÊÎÔÛñçáéíóúàèìòùïüâêîôû]");
                Matcher mpermitido = permitido.matcher(valorActual.substring(valorAnterior.length()));

                if (!mpermitido.find()) {
                    // caracter no permitido, borrarlo
                    campoTexto.setText(valorAnterior);
                    return;
                }
                if (campoTexto.getText().length() > tamañoMáximo) {
                    campoTexto.setText(campoTexto.getText().substring(0, tamañoMáximo));
                }
            }
        }
    });
}

    For those who prefer to use lengthProperty:

    public static void fijarTamañoMáximo(final TextField campoTexto, final int tamañoMáximo) {
    campoTexto.lengthProperty().addListener(new ChangeListener<Number>() {

        @Override
        public void changed(ObservableValue<? extends Number> observable,
            Number valorAnterior, Number valorActual) {          

            if (valorActual.intValue() > valorAnterior.intValue()) {
                Pattern permitido = Pattern.compile("[A-Za-zÑÇÁÉÍÓÚÀÈÌÒÙÏÜÂÊÎÔÛñçáéíóúàèìòùïüâêîôû]");            
                Matcher mpermitido = permitido.matcher(campoTexto.getText().substring(valorAnterior.intValue()));

                if (!mpermitido.find()) {
                    // caracter no permitido, borrarlo                       
                    campoTexto.setText(campoTexto.getText().substring(0, valorAnterior.intValue()));
                    return;                    
                }

                // Revisa que la longitud del texto no sea mayor a la variable definida.
                if (campoTexto.getText().length() >= tamañoMáximo) {
                    campoTexto.setText(campoTexto.getText().substring(0, tamañoMáximo));
                }                   
            }               
        }
    });
}

    Solution a little longer but just as effective.

    • -1