Folders get deleted while run android

I installed 2 plugins the camera & file-chooser

then I ran the

ionic cordova run android command. the whole process went on and the app is launched on my phone. but then I notice the folders camera & file-chooser in @ionic-native gets deleted after the app is launched.

so if i do the run android again, I would get error reporting that these 2 plugins could not be found.

I wonder is this a normal thing to happen?

I think the issue is related with the installation of plugin you have done
try to save the plugin like this

ionic cordova plugin add cordova-plugin-camera
npm install --save @ionic-native/camera

already did that as on the ionic document page. but still same problem