Get the value in entry field then reflect/react to a label in xamarin form - xamarin.forms

Question

My problem is idk how to reflect in a label depending of input value in a entry field by a customer.
To make the things clear, let's start in our database.
Our database
Few information about our realtime database.
In our DELIVERY TABLE, we have 3 types of delivery(standard, reservation and express). In express, by the word itself, it's a rush delivery and we will require a DELIVERY FEE from the customer.
Another table is PRODUCT. We have 2 product for now, MINERAL(PROD1) AND SPARKLING(PROD2). The price of PROD1 is 35 ana PROD2 is 40.
What I've try right now is I put an SelectedIndexChanged in my picker delivery type and picker product type.
//This is my deliverytype event
private async void Picker_DeliveryType_SelectedIndexChanged(object sender, EventArgs e)
{
DELIVERY deliverySave = Picker_DeliveryType.SelectedItem as DELIVERY;
var selectedDeliveryItem = deliverySave.deliveryType;
var note = deliverySave.deliveryFee;
if(selectedDeliveryItem == "Express")
{
await DisplayAlert("Note", "Estimated Delivery: 2 hours from now", "OK");
labelDeliveryFee.Text = "Delivery Fee:" + note;
entryfieldReservationDate.IsEnabled = false;
}
else if(selectedDeliveryItem == "Standard")
{
await DisplayAlert("Note", "Within the day", "OK");
entryfieldReservationDate.IsEnabled = true;
}
else
{
await DisplayAlert("Note", "Enter Reservation Date", "OK");
entryfieldReservationDate.IsEnabled = true;
}
}
//This is my product type event
private void Picker_ProductType_SelectedIndexChanged(object sender, EventArgs e)
{
PRODUCT prod = Picker_ProductType.SelectedItem as PRODUCT;
var selectedProductItem = prod.productType;
var productPricing = prod.productPrice;
if (selectedProductItem == "Mineral")
{
labelProductPrice.Text = Convert.ToString(productPricing);
}
else
{
labelProductPrice.Text = Convert.ToString(productPricing);
}
}
AND my expected output is I want the 2 SelectedIndexChanged will put inside my order button.
//this is my order button click functio now
async private void Button_Clicked(object sender, EventArgs e)
{
if (selectedDeliveryType == "Standard")
{
if (selectedProductItem == "Mineral")
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
else
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
}
else if (selectedDeliveryType == "Reservation")
{
if (selectedProductItem == "Mineral")
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
else
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
}
else
{
int deliveryfee = deliverySave.deliveryFee;
if (selectedProductItem == "Mineral")
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
else
{
//some code here
waterOrder.orderTotalAmount = totalprice;
}
}
//some code here
var SaveData = await waterorderRepos.Save(waterOrder);
var SaveDataToCustomerNotification = await waterorderRepos.SaveCustomerNotification(customerNotification);
if (SaveData)
{
await this.DisplayAlert("Order", "Order successfully", "OK");
ClearData();
CloseAllPopup();
return;
}
else
{
await this.DisplayAlert("Order", "We cannot process your order at the moment.", "OK");
}
}
I will show you some visual presentation between my work now and my expected output.
This is the image.
Please help me guys, idk how to it.Also, no MVVM please cause IDK how to do it. Thank you so much.

Answer 1

Based on the complexity of your code, I recommend that you use the MVVM pattern for implementation.
I created a demo and achieved your function.
You can refer to the following code:
1.create a view model MyViewModel.cs
public class MyViewModel: INotifyPropertyChanged
{
public ObservableCollection<Delivery> Deliveries { get; set; }
private Delivery _deliverySelectedItem;
public Delivery DeliverySelectedItem
{
get => _deliverySelectedItem;
set {
SetProperty(ref _deliverySelectedItem, value);
// update the TotalAmount
caculateTotalAmount();
}
}
public ObservableCollection<Product> Products { get; set; }
//add SelectedItem here
private Product _productSelectedItem;
public Product ProductSelectedItem
{
get => _productSelectedItem;
set {
SetProperty(ref _productSelectedItem, value);
// update the TotalAmount
caculateTotalAmount();
}
}
private int _quantity;
public int Quantity
{
get => _quantity;
set
{
SetProperty(ref _quantity, value);
// update the TotalAmount
caculateTotalAmount();
}
}
private int _totalAmount;
public int TotalAmount
{
get => _totalAmount;
set
{
SetProperty(ref _totalAmount, value);
}
}
private void caculateTotalAmount() {
if (String.IsNullOrEmpty(Quantity.ToString() ) || Quantity == 0) {
TotalAmount = 0;
return;
}
if (ProductSelectedItem!=null && DeliverySelectedItem!=null) {
TotalAmount = ProductSelectedItem.productPrice * Quantity + DeliverySelectedItem.deliveryFee;
}
}
public MyViewModel() {
Products = new ObservableCollection<Product>();
Products.Add(new Product { ProductId = 01, productType = "Products", productPrice = 10 });
Products.Add(new Product { ProductId = 02, productType = "02", productPrice = 12 });
Products.Add(new Product { ProductId = 03, productType = "Products", productPrice = 13 });
Products.Add(new Product { ProductId = 04, productType = "Products", productPrice = 15 });
Deliveries = new ObservableCollection<Delivery>();
Deliveries.Add(new Delivery { deliveryFee = 10, deliveryType = "Express" });
Deliveries.Add(new Delivery { deliveryFee = 20, deliveryType = "Standard" });
Deliveries.Add(new Delivery { deliveryFee = 30, deliveryType = "Standard" });
}
bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
{
if (Object.Equals(storage, value))
return false;
storage = value;
OnPropertyChanged(propertyName);
return true;
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
2.create class Delivery.cs and Product.cs
public class Delivery
{
public string deliveryType { get; set; }
public int deliveryFee { get; set;}
}
public class Product
{
public int ProductId { get; set; }
public string productType { get; set; }
public int productPrice { get; set; }
}
3.MainPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:pickerapp2023112="clr-namespace:PickerApp2023112"
x:Class="PickerApp2023112.MainPage">
<ContentPage.BindingContext>
<pickerapp2023112:MyViewModel></pickerapp2023112:MyViewModel>
</ContentPage.BindingContext>
<StackLayout>
<Picker x:Name="Picker_DeliveryType" ItemsSource="{Binding Deliveries}" ItemDisplayBinding="{Binding deliveryFee}" SelectedItem="{Binding DeliverySelectedItem}"
Title="Select a delivery type"
TitleColor="Red">
</Picker>
<Picker x:Name="Picker_ProductType" ItemsSource="{Binding Products}" ItemDisplayBinding="{Binding productPrice}" SelectedItem="{Binding ProductSelectedItem}"
Title="Select a product type"
TitleColor="Red">
</Picker>
<StackLayout Orientation="Horizontal">
<Label Text="Please input quantity: " BackgroundColor="CadetBlue"/>
<Entry Placeholder="0" Text="{Binding Quantity}" TextColor="Red" HorizontalOptions="FillAndExpand"></Entry>
</StackLayout>
<Label x:Name="labelDeliveryFee" Text="{Binding DeliverySelectedItem.deliveryFee,StringFormat='The delivery free is {0:F1}'}" HorizontalOptions="StartAndExpand" BackgroundColor="Yellow"></Label>
<Label x:Name="labelProductPrice" Text="{Binding ProductSelectedItem.productPrice,StringFormat='The product price is {0:F2}'}" HorizontalOptions="StartAndExpand" BackgroundColor="Yellow"></Label>
<StackLayout Orientation="Horizontal">
<Label Text="The total amount: " BackgroundColor="CadetBlue"/>
<Entry Placeholder="0" Text="{Binding TotalAmount}" TextColor="Red" HorizontalOptions="FillAndExpand"></Entry>
</StackLayout>
</StackLayout>
</ContentPage>
Note:
1.I add two objects for the SelectedItem property of two Pickers and implement interface INotifyPropertyChanged for this ViewModel, if we change the value of the property, the UI will update automatically. The same is true for other properties.
private Delivery _deliverySelectedItem;
public Delivery DeliverySelectedItem
{
get => _deliverySelectedItem;
set {
SetProperty(ref _deliverySelectedItem, value);
}
}
public ObservableCollection<Product> Products { get; set; }
//add SelectedItem here
private Product _productSelectedItem;
public Product ProductSelectedItem
{
get => _productSelectedItem;
set {
SetProperty(ref _productSelectedItem, value);
}
}
In this condition, we don't need add event SelectedIndexChanged for Picker.