Cannot build an Android app with Xamarin

Question

Hi, here is what error is writen when building the app :

1>------ Début de la génération : Projet : Projet CLAC, Configuration : Debug Any CPU ------
C:\Program Files (x86)\Android\android-sdk\emulator\emulator.EXE -no-boot-anim -avd pixel_2_pie_9_0_-_api_28 -prop monodroid.avdname=pixel_2_pie_9_0_-_api_28
Impossible de démarrer l'émulateur pixel_2_pie_9_0_-_api_28.
1>C:\Microsoft\Xamarin\NuGet\xamarin.forms\4.8.0.1451\buildTransitive\Xamarin.Forms.targets(232,5): warning : Xamarin.Forms recommends TargetPlatformMinVersion >= 10.0.14393.0 (current project is -1)
1>C:\Microsoft\Xamarin\NuGet\xamarin.forms\4.8.0.1451\buildTransitive\Xamarin.Forms.targets(238,5): warning : Xamarin.Forms recommends TargetPlatformVersion >= 10.0.17763.0 (current project is -1)
Vérifications à l'exécution effectuées
1>Génération du projet "Projet CLAC.csproj" terminée -- ÉCHEC.
La génération a été annulée.

I don't understand why it doesn't work.

Answer 1

Do you have set the Target platform in the android project properties? It seems it is not defined

Answer 2