update validate field

lib/presentation/screens/actions/dung/widget_dung_supply.dart

 class _WidgetDungSupplyState extends State<WidgetDungSupply> {
   final _dosageController = TextEditingController();
   final _quantityController = TextEditingController();
+  final _howToUseController = TextEditingController();
   final changeSelectedSupply = Get.put(ChangeSupply());
   final changeSupplyUsing = Get.put(ChangeSupplyUsing());
   final changeUnit = Get.put(ChangeUnit());
         return Container();
       } else {
         return Container(
-            height: 80,
+            height: 100,
             child: ListView.builder(
                 physics: ClampingScrollPhysics(),
                 scrollDirection: Axis.horizontal,
                             .updateListByUnitName(editedSupplyUsing.supplyUnit);
                         changeUnit.updateSelected(editedSupplyUsing.supplyUnit);
                         _dosageController.text = editedSupplyUsing.dosage;
+                        _howToUseController.text = editedSupplyUsing.howToUse;
                         _quantityController.text = editedSupplyUsing.quantity
                             .formatNumtoStringDecimal();
                       },
                                   Flexible(
                                       child: Text(
                                           "${value.currentItems[index].quantity.formatNumtoStringDecimal() ?? ""} ${value.currentItems[index].supplyUnit ?? ""}")),
+                                  Flexible(
+                                      child: Text(
+                                          "${value.currentItems[index].howToUse ?? ""}")),
                                 ],
                               ),
                             ),
                         borderRadius: new BorderRadius.circular(8.0)),
                     onPressed: () {
                       var currentSupply = changeSelectedSupply.currentSupply;
-                      if (currentSupply.id != null) {
+                      var currentQuantity =
+                          _quantityController.text.parseDoubleThousand();
+                      if (currentSupply.id != null && currentQuantity > 0) {
                         var quantityWithCurrentSupplyUnit =
                             UtilAction.convertUnit(
-                                inputValue: _quantityController.text
-                                    .parseDoubleThousand(),
+                                inputValue: currentQuantity,
                                 oldUnit: changeUnit.selectedUnit,
                                 newUnit:
                                     changeSelectedSupply.currentSupply.unit);
                         SuppliesUsing newSup = SuppliesUsing()
                           ..dosage = _dosageController.text
+                          ..howToUse = _howToUseController.text
                           ..quantity = quantityWithCurrentSupplyUnit
                           ..tbSuppliesInWarehouseId = currentSupply.id
                           ..suppliesInWarehouseId = currentSupply.id
                         borderRadius: new BorderRadius.circular(8.0)),
                     onPressed: () {
                       var currentSupply = changeSelectedSupply.currentSupply;
-                      if (currentSupply.id != null) {
+                      var currentQuantity =
+                          _quantityController.text.parseDoubleThousand();
+                      if (currentSupply.id != null && currentQuantity > 0) {
                         var quantityWithCurrentSupplyUnit =
                             UtilAction.convertUnit(
-                                inputValue: _quantityController.text
-                                    .parseDoubleThousand(),
+                                inputValue: currentQuantity,
                                 oldUnit: changeUnit.selectedUnit,
                                 newUnit:
                                     changeSelectedSupply.currentSupply.unit);
                         SuppliesUsing newSup = SuppliesUsing()
                           ..dosage = _dosageController.text
+                          ..howToUse = _howToUseController.text
                           ..quantity = quantityWithCurrentSupplyUnit
                           ..tbSuppliesInWarehouseId = currentSupply.id
                           ..suppliesInWarehouseId = currentSupply.id
             Container(
               width: double.infinity,
               child: Text(
-                "Tên thương mại",
+                "Tên thương mại *",
                 style: TextStyle(color: Colors.black54, fontSize: 13.0),
               ),
             ),
                         child: _dropdownUnitTypes(),
                       )),
                 ]),
+            TextFormField(
+              keyboardType: TextInputType.text,
+              controller: _howToUseController,
+              decoration: InputDecoration(labelText: "Phương pháp sử dụng"),
+              onSaved: (newValue) {},
+            ),
             _buttonInForm()
           ],
         ));
     changeSupplyUsing.changeIndexEdit(-1);
     changeButton.resetValue();
     _dosageController.text = "";
+    _howToUseController.text = "";
     _quantityController.text = "";
     changeUnit.initValue();
     changeSelectedSupply.initValue();