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Richard
Asked: 2020-07-02 15:34:27 +0800 CST 2020-07-02 15:34:27 +0800 CST

How to validate a TextField after losing focus?

  • 772

Currently I perform the validation using onChange, but my intention is that when the user moves to another text field, TextFieldwhen it loses focus , it will be validated and show an error message if there is one.

new TextField(
          controller: textController,
      decoration: new InputDecoration(
        hintText: 'Email',
        border: InputBorder.none ,
        labelText: 'Ingrese su Email',
        errorText: _validate ? "Dato no valido" : null
      ),
      keyboardType:TextInputType.emailAddress,
      onChanged: (validate){
       setState(() {
        if (validanco(validate)) {
          _validate = false;
        }else _validate = true;
        });
      },
      onEditingComplete: () =>FocusScope.of(context).requestFocus(focusnobe),
    ),

The method validanco()returns a type value boolwhich, if ok, returns the text true.

Look for the documentation of FocusNodebut I did not find any method that helps me to validate when the user changes fromTtextField

validación

1 Answers

  1. Best Answer

    What you need to do is create a FocusNode, assign it to your , TextFieldand add a listener to it FocusNodeto listen for focus changes.

      //Declarando el focusNode
  FocusNode _focusEmail =FocusNode();


  @override
  void initState() {
    //escuchando cambios de foco
    _focusEmail.addListener(() {

      if (_focusEmail.hasFocus){
        print("tiene el foco");
      } else {
        print("perdió el foco");
      }

    },);
    super.initState();
  }

    Assigning focus:

    TextField(
         focusNode: _focusEmail,
          controller: textController,
          ...
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