Problema em somar valores de um Listview Xamarin

Question

User379132 posted

Olá pessoal, estou com uma dificuldade em somar os valores exibido dentro de um ListView e exibir em uma Label;

A Idea é bem simples, (exemplo) eu carrego 5 linhas do ListView com valores distintos (1 ,2, 3, 4, 5) e preciso obter a soma destes valores ( total 15 ) para informar numa Label, já utilizei um FOR mas o ListView não aceita listView.Items[i]; exatamente o ".Items".

Alguém pode ajudar em obter essa soma?

Obrigado!!

Answer 1

User359363 posted

First, please use English to describe your question.

Second, you should do it in your view model. Here is an simple example:

My View Model: ``` class Product { public string Name { get; set; } public double Number { get; set; } }

class ProductVM : INotifyPropertyChanged
{
    double _totalNumber;
    List<Product> _products;

    public event PropertyChangedEventHandler PropertyChanged;

    public List<Product> Products
    {
        set
        {
            if (_products != value)
            {
                _products = value;
                OnPropertyChanged("Products");
                Recalculate();
            }
        }
        get
        {
            return _products;
        }
    }

    public string Intro
    {
        get
        {
            return "Product Header";
        }
    }

    public double TotalNumber
    {
        set
        {
            if (_totalNumber != value)
            {
                _totalNumber = value;
                OnPropertyChanged("TotalNumber");
            }
        }
        get
        {
            return _totalNumber;
        }
    }

    void Recalculate()
    {
        foreach(Product price in Products)
        {
            this.TotalNumber += price.Number;
        }
        //.TotalPrice = this.Price * this.Quantity;
    }

    protected void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

```

ListViewPage.xaml:

<ListView x:Name="listView" ItemsSource="{Binding Products}" Header="{Binding Intro}" Footer="{Binding TotalNumber}"> <ListView.HeaderTemplate > <DataTemplate> <StackLayout Orientation="Horizontal" Padding="10,5,5,10" BackgroundColor="Yellow"> <Label Text="~~"/> <Label Text="{Binding .}"/> <Label Text="~~"/> </StackLayout> </DataTemplate> </ListView.HeaderTemplate> <ListView.ItemTemplate> <DataTemplate> <TextCell Text="{Binding Name}" Detail="{Binding Number}"></TextCell> </DataTemplate> </ListView.ItemTemplate> </ListView>

ListViewPage.xaml.cs: ``` public partial class ListViewPage : ContentPage { public ListViewPage() { InitializeComponent();

        var products = new List<Product> {
            new Product {Name = "Xander", Number = 1},
            new Product {Name = "Rupert", Number = 2},
            new Product {Name = "Tammy", Number = 3},
            new Product {Name = "Blue", Number = 4},
        };

        BindingContext = new ProductVM { Products = products };
    }
}

```

Answer 2

User379132 posted

@YorkGo,

Muito obrigado pela ajuda, exatamente, isso deu certo!! Valeu amigo!

Feliz 2019