how to work with activity indicator until listview loaded xamarin form

Question

I am binding listview from web service, now some time listview take time to load depend on internet connection, i need activity indicator keep running until listview is load. here is my code

xaml

<ListView x:Name="ReportListView" ItemsSource="{Binding ReportList}"
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <StackLayout Padding="9" HorizontalOptions="StartAndExpand" Orientation="Vertical" BackgroundColor="Lavender">
                    <Label Text="{Binding ReportName}" FontSize="Medium" WidthRequest="10000" TextColor="Blue" Style="{DynamicResource ListItemTextStyle}" />
                </StackLayout
            </ViewCell>
        </DataTemplate>
   </ListView.ItemTemplate>
</ListView>

<ActivityIndicator HorizontalOptions="Center" VerticalOptions="Center" IsRunning="False" IsVisible="False" x:Name="activity"/>

i am working like this which is absolutely not correct

.cs

activity.IsVisible = true;
activity.IsRunning = true;
wait.IsVisible = true;
progressControl.IsVisible = true;
ReportListView.IsVisible = false;
Task.Delay(5000);
BindingContext = new MainViewModel();

activity.IsVisible = false;
activity.IsRunning = false;
wait.IsVisible = false;
progressControl.IsVisible = false;

ReportListView.IsVisible = true;

with this code activity indicator run for 5 sec and disappear and listview load depends on network connection. How can i work where activity indicator keep running until listview load?

Bind your IsVisible and IsRunning to something that gets set from the actual networking code instead of using Task.Delay(5000) — Biesi
– Biesi, Commented May 11, 2018 at 12:24

Valeriy Kovalenko · Accepted Answer · 2018-05-11 12:31:44Z

3

A common approach is to bind the IsVisible property of the ActivityIndicator to some IsBusy or IsLoading property of your view model.

XAML:

<ListView x:Name="ReportListView" ItemsSource="{Binding ReportList}">
    ...
</ListView>
<ActivityIndicator IsRunning="{Binding IsBusy}" IsVisible="{Binding IsBusy}" />

ViewModel:

bool isBusy;
public bool IsBusy
{
    get => isBusy; 
    set 
    { 
        isBusy = value; 
        OnPropertyChanged(); 
    }
}

async Task LoadItemsAsync()
{
    try
    {
        IsBusy = true;

        // Call your web service here
        var items = await service.LoadSomthingAsync();
    }
    catch (Exception ex)
    {
        // Handle exception
    }
    finally
    {
        IsBusy = false;
    }
}

In this case, each time when you set IsBusy to true, the app will show a loading indicator.

answered May 11, 2018 at 12:31

Valeriy Kovalenko

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Comments

Sayo Komolafe · Accepted Answer · 2018-05-11 20:18:59Z

0

In your xaml, you should bind the IsRunning property of your ActivityIndicator to your listview

<ListView x:Name="ReportListView" ItemsSource="{Binding ReportList}"
<ListView.ItemTemplate>
    <DataTemplate>
        <ViewCell>
            <StackLayout Padding="9" HorizontalOptions="StartAndExpand" Orientation="Vertical" BackgroundColor="Lavender">
                <Label Text="{Binding ReportName}" FontSize="Medium" WidthRequest="10000" TextColor="Blue" Style="{DynamicResource ListItemTextStyle}" />
            </StackLayout
        </ViewCell>
    </DataTemplate>
  </ListView.ItemTemplate>
</ListView>
<ActivityIndicator HorizontalOptions="Center" VerticalOptions="Center" 
 IsRunning="{Binding Source={x:Reference ReportListView}, Path=IsLoading}" 
 x:Name="activity"/>

Then, in your code behind, on initialization, set the IsVisible, IsEnabled and IsRunning to true

For example

public ListViewPage()
    {
        InitializeComponent();
        activity.IsVisible = true;
        activity.IsRunning = true;
        activity.IsEnabled = true;
    }

You can then handle hiding your activityIndicator as below

protected override void OnAppearing()
    {
        ReportListView.ItemsSource = //your items;
        reportIndicator.IsVisible = false;
        reportIndicator.IsRunning = false;
        reportIndicator.IsEnabled = false;

        base.OnAppearing();            
    }

edited May 11, 2018 at 20:18

answered May 11, 2018 at 16:09

Sayo Komolafe

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1 Comment

quemeful Over a year ago

@OlorunfemiAjibulu not picking on you, but that statement shows where good modern programming has gone. All terminology and standards and no depth. Knowing the terminology for MVVM but not knowing how to take this example and build a working MVVM version of it.

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