如何在angularjs中聚焦表格中的文本框？

角度js代码：ng onchange代码

html表格代码

{{item.ProductName}
{{item.ProductRate}
{{item.TotalAmount}
总计{{gridproducts[0].TotalBill}}总计项目25

 $scope.txtqty = function (item) {
        var id = item.Id;
        $http.put("/api/Products/txtqty/" + id, item).then(function (response) {
            $scope.gridproducts = response.data;
        })
    }

 <tbody>
                                                    <tr ng-repeat="item in gridproducts">
                                                        <td ng-click="griddelete(item.Id)"><a class="delete"><i class="fa fa-times-circle-o"></i></a></td>
                                                        <td class="name">{{item.ProductName}}</td>
                                                        <td>{{item.ProductRate}}</td>
                                                        <td><input class="form-control qty" type="text" style="width:50px" ng-change="txtqty(item)" ng-model="item.ProductQty" value="{{item.ProductQty}}"></td>
                                                        <td>{{item.TotalAmount}}</td>
                                                    </tr>
                                                    <tr></tr>
                                                <tfoot><tr><th colspan="2"></th><th colspan="2"><b>Total</b></th><th><b>{{gridproducts[0].TotalBill}}</b></th></tr><tr><th colspan="2"><b></b></th><th colspan="2"><b>Total Items</b></th><th><b>25</b></th></tr></tfoot>
                                            </table>