如何使用prestashop的post api使用react-native将产品添加到购物车中？ 这是我在react-native中使用的代码

addtocart = () => {
      console.log("adding to cart");
      //  const addtocarturl = "BFFRCL879WV8RDF35DY5MLVEMG19IKTJ@ec2-3-16-44-207.us-east-2.compute.amazonaws.com/api/carts?schema=blank";
      // this.navigate.addtocarturl
      // http://ec2-3-16-44-207.us-east-2.compute.amazonaws.com/api/carts?ws_key=BFFRCL879WV8RDF35DY5MLVEMG19IKTJ&schema=blank
      fetch('http://ec2-3-16-44-207.us-east-2.compute.amazonaws.com/api/carts?ws_key=BFFRCL879WV8RDF35DY5MLVEMG19IKTJ&schema=blank',{
  method: 'POST',headers: { 
    "async": true,"crossDomain": true,'accept': "*/*",'Content-Type': 'application/xml',// <-- Specifying the Content-Type
    "Authorization": "Basic QkZGUknmODc5V1Y4UkRGMzVEWTVNTFZFTUcxOUlLVEo6","Host": "ec2-3-16-44-207.us-east-2.compute.amazonaws.com","Connection": "keep-alive","cache-control": "no-cache",},body: <prestashop>
    <cart>
    <id_address_delivery>10</id_address_delivery>
    <id_address_invoice>10</id_address_invoice>
    <id_currency >1</id_currency>
    <id_customer>19</id_customer>
    <id_lang >1</id_lang>
    <delivery_option/>
    <secure_key/>
    <allow_seperated_package>0</allow_seperated_package>
    <date_add>2015-06-23 14:45:08</date_add>
    <date_upd>2015-06-23 14:45:08</date_upd>
    <associations><cart_rows>
    <cart_row>
    <id_product>50</id_product>
    <id_product_attribute >0</id_product_attribute>
    <id_address_delivery >10</id_address_delivery>
    <quantity>7</quantity>
    </cart_row>
    </cart_rows>
    </associations>
    </cart>
    </prestashop>
})

.then((responseData) => { console.log(responseData) })
.catch((err) => { console.log(err); });
}

此发布方法用于将产品添加到购物车中。 它的抛出错误： 不变违规：不能用作本机方法参数