Flutter-password-visibility.dart

Initiate passwordVisible to false in initState()

@override
  void initState() {
    passwordVisible = false;
  }
Following is the TextFormField widget :

TextFormField(
   keyboardType: TextInputType.text,
   controller: _userPasswordController,
   obscureText: passwordVisible,//This will obscure text dynamically
   decoration: InputDecoration(
       labelText: 'Password',
       hintText: 'Enter your password',
       // Here is key idea
       suffixIcon: IconButton(
            icon: Icon(
              // Based on passwordVisible state choose the icon
               passwordVisible
               ? Icons.visibility
               : Icons.visibility_off,
               color: Theme.of(context).primaryColorDark,
               ),
            onPressed: () {
               // Update the state i.e. toogle the state of passwordVisible variable
               setState(() {
                   passwordVisible = !passwordVisible;
               });
             },
            ),
          ),
        );