title: How to use setState without StatefulWidget?
body: <p>First of all i know it's not really posible to do it, but I have a problem and I don't know what to do.
  I want to use DropDown but it wont change the text without the setState and i cant convert this code to a StatefulWidget. What should i do? The code dosen't reallly matter, but here it is(not the whole code):</p>
  
  <pre><code>  Widget buildAboutDialog(
        BuildContext context, _myHomePageState, bool isEdit, Clothes clothes){
      if(clothes != null){
        this.clothes = clothes;
        teCategoryName = clothes.category;
        teBrandName.text = clothes.brand;
        teColorName.text = clothes.color;
        teSizeName.text = clothes.size;
        teQtyName.text = clothes.qty;
      }
     return new AlertDialog(
        title: new Text(isEdit ? 'Edit' : 'Add new Clothes'),
        content: new SingleChildScrollView(
          child: new Column(
            mainAxisSize: MainAxisSize.min,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: &lt;Widget&gt;[
              Container(
  
                child: Center(
                  child: DropdownButton(
                    hint:  Text("Choose Category"),
                    value: teCategoryName,
                    isExpanded: true,
                    onChanged: (newValue){
                      teCategoryName = newValue;
                      **setState(() {
                        teCategoryName = newValue;
                      });**
  
                    },
                    items: _categorynames.map((location){
                      return DropdownMenuItem(
                        child: new Text(location),
                        value: location,
                      );
                    }).toList(),
  
                  ),
                ),
              ),
  </code></pre>