Set QLineEdit to accept only numbers

Question

I have a QLineEdit where the user should input only numbers    So is there a numbers-only setting for QLineEdit

User · Answer

If you re using QT Creator 5 6 you can do that like this    include  lt QIntValidator gt   ui- gt myLineEditName- gt setValidator  new QIntValidator     I recomend you put that line after ui- setupUi this    I hope this helps

User · Answer

The best is QSpinBox   And for a double value use QDoubleSpinBox   QSpinBox myInt  myInt setMinimum -5   myInt setMaximum 5   myInt setSingleStep 1     Will increment the current value with 1  if you use up arrow key   if you use down arrow key   gt  -1  myInt setValue 2     Default begining value myInt value      Get the current value   connect  amp myInt  SIGNAL valueChanged int    this  SLOT myValueChanged int

User · Answer

Why don t you use a QSpinBox for this purpose   You can set the up down buttons invisible with the following line of codes          QSpinBox  spinBox   new QSpinBox  this    spinBox- gt setButtonSymbols  QAbstractSpinBox  NoButtons       After this it looks just like a QLineEdit

User · Answer

The Regex Validator  So far  the other answers provide solutions for only a relatively finite number of digits  However  if you re concerned with an arbitrary or a variable number of digits you can use a QRegExpValidator  passing a regex that only accepts digits  as noted by user2962533 s comment   Here s a minimal  complete example    include  lt QApplication gt   include  lt QLineEdit gt   include  lt QRegExpValidator gt   int main int argc  char  argv          QApplication app argc  argv        QLineEdit le      le setValidator new QRegExpValidator QRegExp   0-9       amp le        le show         return app exec        The QRegExpValidator has its merits  and that s only an understatement   It allows for a bunch of other useful validations   QRegExp   1-9  0-9            leading digit must be 1 to 9  prevents leading zeroes   QRegExp    d                  allows matching for unicode digits  e g  for                                  Arabic-Indic numerals such as       QRegExp   0-9                 input must have at least 1 digit  QRegExp   0-9  8 32           input must be between 8 to 32 digits  e g  for some basic                                 password special-code checks   QRegExp   0-1   4             matches at most four 0s and 1s  QRegExp  0x 0-9a-fA-F         matches a hexadecimal number with one hex digit  QRegExp   0-9  13             matches exactly 13 digits  e g  perhaps for ISBN    QRegExp   0-9  1 3     0-9  1 3     0-9  1 3     0-9  1 3                                  matches a format similar to an ip address                                  N B  invalid addresses can still be entered   999 999 999 999          More On Line-edit Behaviour  According to documentation      Note that if there is a validator set on the line edit  the returnPressed   editingFinished   signals will only be emitted if the validator returns QValidator  Acceptable    Thus  the line-edit will allow the user to input digits even if the minimum amount has not yet been reached  For example  even if the user hasn t inputted any text against the regex   0-9  3     which requires at least 3 digits   the line-edit still allows the user to type input to reach that minimum requirement  However  if the user finishes editing without satsifying the requirement of  at least 3 digits   the input would be invalid  the signals returnPressed   and editingFinished   won t be emitted    If the regex had a maximum-bound  e g    0-1   4     then the line-edit will stop any input past 4 characters  Additionally  for character sets  i e   0-9    0-1    0-9A-F   etc   the line-edit only allows characters from that particular set to be inputted   Note that I ve only tested this with Qt 5 11 on a macOS  not on other Qt versions or operating systems  But given Qt s cross-platform schema     Demo  Regex Validators Showcase

User · Answer

You could also set an inputMask   QLineEdit setInputMask  9     This allows the user to type only one digit ranging from 0 to 9  Use multiple 9 s to allow the user to enter multiple numbers  See also the complete list of characters that can be used in an input mask    My answer is in Python  but it should not be hard to transform it to C

User · Answer

QLineEdit  setValidator    for example   myLineEdit- gt setValidator  new QIntValidator 0  100  this       or  myLineEdit- gt setValidator  new QDoubleValidator 0  100  2  this       See  QIntValidator  QDoubleValidator  QLineEdit  setValidator

[c++] Set QLineEdit to accept only numbers

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