CODEWITHSUNDEEP
c#visual-studioxamarinbinding
S Kirchner
S Kirchner

Reputation: 123

Xamarin Binding Data from ItemSource to a Labels Text

i´ve got 2 things: second one is a list. when i´m clicking the "+1" button, a new element is createt with the name "list.Count"(so first one is 1, 2, 3, 4...). this is working very good. but for the first thing i wanna have only the vurrent value of the "Text"(from the current newest object in the list). But: i do not only want a counter. Maybe you can unterstand better if you check out my code:

<StackLayout>
<StackLayout>
    <StackLayout Orientation="Horizontal" >
        <Label Text="Erg:" HorizontalOptions="StartAndExpand" VerticalOptions="StartAndExpand" />
        <Label Text="{Binding Path=Nummer, Source=Num}" HorizontalOptions="EndAndExpand" VerticalOptions="StartAndExpand" /> *
    </StackLayout>
        <Button Text="+1" Command="{Binding CountUpCommand}" />  **
    <Button Text="Erg x Erg" />
</StackLayout>
<Label Text="--------------" />
<StackLayout>
    <ListView ItemsSource="{Binding Nummer}"> **
        <ListView.ItemTemplate>
            <DataTemplate>
                <TextCell 
                Text="{Binding Num}" **
                />
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackLayout>
</StackLayout>

so my question is at the Line with only one * at the end. the other 3 lines with two ** are working. what do i have to do to get the right Binding-Path or -Statment or something like this, to get the number shown up at labelsText ? i think there´s something missing like "itemsource"..

so here s the code from Itemsource (from My CounterVM):

    public ObservableCollection<NumberViewModel> Nummer { get; private set; } = new ObservableCollection<NumberViewModel>();


    public ICommand CountUpCommand { get; private set; }

    public CounterViewModel()
    {

        CountUpCommand = new Command(CountUp);
    }


    public void CountUp()
    {
        int newNumber = Nummer.Count + 1;
        Nummer.Add(new NumberViewModel { Num = newNumber});
    }

and here the NumverVM, same code as in number.cs:

public class NumberViewModel : BaseViewModel
{
    public int Num { get; set; }
}

Upvotes: 0

Views: 145

Answers (1)

DirtyNative
DirtyNative

Reputation: 2834

You can add a Property inside your ViewModel to get the correct value:

public class CounterViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    public string LastItemsText => Nummer.Last()?.Num.ToString();

    public ObservableCollection<NumberViewModel> Nummer { get; private set; } = new ObservableCollection<NumberViewModel>();

    public ICommand CountUpCommand { get; private set; }

    public CounterViewModel()
    {
        CountUpCommand = new Command(CountUp);
    }

    public void CountUp()
    {
        int newNumber = Nummer.Count + 1;
        Nummer.Add(new NumberViewModel { Num = newNumber});
        PropertyChanged(this, new PropertyChangedEventArgs(nameof(LastItemsText));
    }
}

And instead of 

<Label Text="{Binding Path=Nummer, Source=Num}"

do this:

<Label Text="{Binding LastItemsText}"

Upvotes: 1

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