title: How to set Country code before the phone number with flutter?
body: <p>I'm trying to putting the country code before the phone number.
  I used<code>country_pickers</code> package but something gone wrong with my code,
  my TextField's hintText visibility has gone, it's showing nothing</p>
  
  <p>here is my widget</p>
  
  <pre><code> Padding(
                        padding: const EdgeInsets.only(top: 5.0),
                          child:  new Container(
                            padding: const EdgeInsets.only(left: 10.0),
                          decoration: BoxDecoration(
                            borderRadius: BorderRadius.all(Radius.circular(5.0)),
                            border: Border.all(color: Colors.blue)
                          ),  
                          child: TextField(
  
                            keyboardType: TextInputType.phone,
                            decoration: InputDecoration(
                              border: InputBorder.none,
                              hintText: "Phone Number",
                              prefix:  CountryPickerDropdown(
                                initialValue: 'in',
                                itemBuilder: _buildDropdownItem,
                                onValuePicked: (Country country) {
                                  print("${country.name}");
                                },
                              ),
                            ),
                            onChanged: (value){
                              this.phoneNo=value;
                            },
  
                          ),  
                        ),
                      ),
  </code></pre>
  
  <p>here's  widget method for country code</p>
  
  <pre><code>Widget _buildDropdownItem(Country country) =&gt; Container(
          child: Row(
            children: &lt;Widget&gt;[
              CountryPickerUtils.getDefaultFlagImage(country),
              SizedBox(
                width: 8.0,
              ),
              Text("+${country.phoneCode}(${country.isoCode})"),
            ],
          ),
        );
  </code></pre>