How can I add validation to not enabled textformfeld? - flutter

Question

im trying to displaying error text when textformfield is empty and this is working fine but only when user tapping on the textfield he is seeing the error . What I want is if user tap upload video and the textfomrfield for the hashtag is empty then showing error text so also when its not enabled .
Hope anyone can help
Here is my code
Container(
width: 170,
height: 65,
margin: EdgeInsets.only(left: 12, right: 10),
child: TextFormField(
controller: hashtagcontroller2,
decoration: InputDecoration(
hintText: 'Hashtag',
prefixText: '#',
contentPadding: EdgeInsets.fromLTRB(12, 8, 8, 8),
errorText: _validatehashtag2 ? 'Hashtag Can\'t Be Empty' : null,
border: OutlineInputBorder(
borderRadius: const BorderRadius.all(
const Radius.circular(10.0),
),
borderSide: BorderSide(
width: 2, color: Colors.black),
),
focusedBorder: OutlineInputBorder(
borderRadius: const BorderRadius.all(
const Radius.circular(20.0),
),
borderSide: BorderSide(
width: 2, color: Colors.black),
),//prefixIcon: Icon(Icons.h)
),
),
),
``

Answer 1

First you bind the container with column and try out
Column(
children: [
Container(
width: 170,
height: 65,
margin: EdgeInsets.only(left: 12, right: 10),
child: TextFormField(
controller: hashtagcontroller2,
decoration: InputDecoration(
hintText: 'Hashtag',
prefixText: '#',
contentPadding: EdgeInsets.fromLTRB(12, 8, 8, 8),
errorText: _validatehashtag2 ? 'Hashtag Can\'t Be Empty' : null,
border: OutlineInputBorder(
borderRadius: const BorderRadius.all(
const Radius.circular(10.0),
),
borderSide: BorderSide(
width: 2, color: Colors.black),
),
focusedBorder: OutlineInputBorder(
borderRadius: const BorderRadius.all(
const Radius.circular(20.0),
),
borderSide: BorderSide(
width: 2, color: Colors.black),
),//prefixIcon: Icon(Icons.h)
),
),
),
RaisedButton(
onPressed: () {
setState(() {
hashtagcontroller2.text.isEmpty ? _validatehashtag2 = true : _validatehashtag2 = false;
});
},
child: Text('Submit'),
textColor: Colors.white,
color: Colors.blueAccent,
),],),