Multi tool use

Activity Indicator is dismissed before images are loaded

I have a question. My activity Indicator dismisses before my images are finished loading from my api. Is it because the call to the api is async? If so, how can I make sure the call is done or the images are loaded on the screen before dismissing my activity indicator?

The activity indicator code in my XAML looks like this:

<ActivityIndicator IsRunning="{Binding IsBusy}"
IsVisible="{Binding IsBusy}"
VerticalOptions="Center"
HorizontalOptions="Center"/>


My property (which is located in viewmodel base):

private bool isBusy;
public bool IsBusy
{
get { return isBusy; }
set { SetProperty(ref isBusy, value); }
}


And this is the code where I set the property:

public override async void OnNavigatingTo(NavigationParameters navParams)
{
if(navParams.ContainsKey("query"))
{
var query = (string)navParams["query"];
IsBusy = true;
await DisplayImages(query);
IsBusy = false;

}
}


Thanks!

DisplayImages

2 Answers
2

I'm not at my computer, and it's tricky to do on this device, but here goes...

Option 1: BackgroundWorker

Async/await doesn't make it run on a background thread, you need the loading to occur on a background thread. And be aware that Tasks and threads are different.

Create a field on your class, type BackgroundWorker. Hook up the DoWork event of that field to be a method containing:

BackgroundWorker

IsBusy = true;
DisplayImages(query);
IsBusy = false;


And where those lines used to be, call RunWorkerAsync on your field. You can put the value of query into a field so it can be used from the DoWork method.

RunWorkerAsync

query

Option 2: an actual thread

Put the 3 lines in a method called Load(string query). Where those lines used to be, do this:

Load(string query)

myNewThread = new Thread(() => Load(query));
myNewThread.Start();


I think myNewThread needs to be a field so it doesn't get garbage collected.

myNewThread

Implement in your method using:

Device.BeginInvokeOnMainThread(async () =>
{
//load your images here
//Lastly set IsBusy to false
});


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