Xamarin.Forms: how to display a Lottie animation at least one time when IsBusy is true during data loading?

Question

On my Xamarin.Forms project, I would like to display a Lottie animation during API calls or during the loading of a we

Answer 1

I've found another approach that works, even if this solution is a bit heavy and can be improved.

Firstly, as recommended there, I've created 2 Triggers:

public class PlayLottieAnimationTriggerAction : TriggerAction<AnimationView>
{
    protected override void Invoke(AnimationView sender)
    {
        Debug.WriteLine($"PlayLottieAnimationTriggerAction()");
        sender.PlayAnimation();
    }
}

public class StopLottieAnimationTriggerAction : TriggerAction<AnimationView>
{
    protected override void Invoke(AnimationView sender)
    {
        Debug.WriteLine($"StopLottieAnimationTriggerAction()");
        sender.StopAnimation();
    }
}

I also used EventToCommandBehaviors, like described there.

After this I can use the Lottie animation like this:

<forms:AnimationView 
    x:Name="animationView" 
    BackgroundColor="Transparent"
    AutoPlay="True"
    IsVisible="{Binding ShowAnimation}"
    Animation="resource://lottie_4squares_apricot_blond.json?assembly=Example.Forms"
    AnimationSource="EmbeddedResource"
    VerticalOptions="FillAndExpand" 
    HorizontalOptions="FillAndExpand">
    <forms:AnimationView.Triggers>
        <MultiTrigger TargetType="forms:AnimationView">
            <MultiTrigger.Conditions>
                <BindingCondition Binding="{Binding ShowAnimation}" Value="True" />
            </MultiTrigger.Conditions>
            <MultiTrigger.EnterActions>
                <triggers:LottieTriggerAction />
            </MultiTrigger.EnterActions>
            <MultiTrigger.ExitActions>
                <actions:StopLottieAnimationTriggerAction />
            </MultiTrigger.ExitActions>
        </MultiTrigger>
    </forms:AnimationView.Triggers>
    <forms:AnimationView.Behaviors>
        <behaviors:EventToCommandBehavior
            EventName="OnFinishedAnimation"
            Command="{Binding OnFinishedAnimationCommand}"
            CommandParameter="{x:Reference animationView}"/>
    </forms:AnimationView.Behaviors>
</forms:AnimationView>

And in my ViewModel, I've declared a property ShowAnimation that is related to IsBusy and the Command OnFinishedAnimationCommand like this:

private bool _showAnimation;
public bool ShowAnimation
{
    get => _showAnimation;
    set => Set(ref _showAnimation, value);
}

public ICommand OnFinishedAnimationCommand
{
    get
    {
        return new Xamarin.Forms.Command<object>(async (object sender) =>
        {
            if (sender != null)
            {
                await OnFinishedAnimation(sender);
            }
        });
    }
}

private Task OnFinishedAnimation(object sender)
{
    var view = sender as AnimationView;
    if (IsBusy)
    {
        view.PlayAnimation();
    }
    else
    {
        ShowAnimation = false;
    }
    return Task.CompletedTask;
}

In case of the Loader is related to a WebView, the ShowLoadingView property is set like this:

private Task WebViewNavigatingAsync(WebNavigatingEventArgs eventArgs)
{
    IsBusy = true;
    ShowLoadingView = true;
    return Task.CompletedTask;
}

private async Task WebViewNavigatedAsync(WebNavigatedEventArgs eventArgs)
{
    IsBusy = false;
}

But, as I also display an ErrorView in case of issues (timeout, unreachable server, ...) and a Reload/Retry button, I had to add some code:

private async Task WebViewNavigatedAsync(WebNavigatedEventArgs eventArgs)
{
    IsBusy = false;
    // for display loading animation on Refresh
    while (ShowLoadingView)
        await Task.Delay(50);
    SetServiceError();
}

In case of the Loader is related to Data loading, the ShowLoadingView property is set like this:

private async Task GetNewsAsync(bool forceRefresh = false)
{
    try
    {
        ShowErrorView = false;
        ErrorKind = ServiceErrorKind.None;
        IsBusy = true;
        ShowLoadingView = true;
        var _news = await _dataService.GetNews(forceRefresh);
        News = new ObservableCollection<News>(_news);
    }
    catch (Exception ex)
    {
        ErrorKind = ServiceErrorKind.ServiceIssue;
    }
    finally
    {
        IsBusy = false;
        await SetServiceError();
    }

}

However, I noticed that in some cases the SetServiceError() was not fired, as OnFinishedAnimation() was called in the same time. I haven't yet investigated, but I've fixed this by adding the call to SetServiceError() in in OnFinishedAnimation():

private async Task OnFinishedAnimation(object sender)
{
    var view = sender as AnimationView;
    if (IsBusy)
    {
        view.PlayAnimation();
    }
    else
    {
        ShowLoadingView = false;
        // fix SetServiceError() call issue
        await SetServiceError();
    }
}

Don't hesitate to tell what could be done to optimize this.

Answer 2

I would like to display a Lottie animation during API calls

public async void loadData()
{
    //Data load started
    viewModel.IsBusy = true;

    await methodOfLoadingData...;

    //Data load finished
     viewModel.IsBusy = false;
}

during the loading of a website in a WebView：

private void MyWebView_Navigating(object sender, WebNavigatingEventArgs e)
{
    viewModel.IsBusy = true;
}

private void MyWebView_Navigated(object sender, WebNavigatedEventArgs e)
{
    viewModel.IsBusy = false;
}

But the loading duration is sometimes very short

The loading duration is depending on the time you completely loading the data/webview. If you load the data/webview very fast, the loading duration should be short.