I need a JTextField can only accept values of both negative and positive numbers but I can not get the '-'. I've already tried several things.
private void JTPtxKeyTyped(java.awt.event.KeyEvent evt) {
char a = evt.getKeyChar();
if ((a<'0' || a>'9' || /*FALTA LA INSTRUCCION PARA ACEPTAR EL MENOS*/)) evt.consume();
}
I recommend starting the validation of the character in two parts.
Part 1: if the character is '-' and if the content of the JTextField is empty, then it is valid.
Part 2: if the character is a digit, it is valid.
In code, this would be something like (note, this code can be greatly reduced):
char a = evt.getKeyChar();
boolean valido = false;
if (a == '-') {
Object component = evt.getComponent();
if (component instanceof JTextField) {
JTextField tf = (JTextField)component;
valido = tf.getText().isEmpty();
}
} else if (a >= '0' && a <= '9') {
valido = true;
}
if (!valido) {
evt.consume();
}
You could work with jspiner and it would no longer be necessary to create anything See here