What happens if I receive the push notification when the app is launched

I would like to know what happens if I receive the push notification when the app is launched.

Is it a default behavior in ios or Android like the notification will slide in from the top when the app is launched?

or

Will the push notification not show if the app is launched?

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I am working the UI flow. Originally, I use toast to remainder the users when the app is launched, and I use push notification to remainder the users when the app is not launched. However, if I have no idea if I use push notification , does any notification show when the app is notification? I push notification will notice user when the app is launched, then I will not use toast.

Really appreciate!!