@mark4jets thank you for your answer.
I have seen your link but like you, i'm not a developer.
I just need to unlock an easy action to launch the action "shoot a photo" in any app that permit to take a photo with volume button for example.
I know that there is a way to do it but i don't know which is the best one without write code.
I make an example, Flic app permits to read a sentence and my native camera app permits to shoot a photo with a voice command. So now, i have create the action to say "capture". So i open my camera app, i set every parameters and next with flic button i shoot the photo reading the sentence "capture".
It's absolutely an ugly way to take a photo ahahah that's why i would like to improve this function.
I think that simulate physical buttons could solve this problem in a better way.

Or maybe these solutions

https://developer.android.com/training/camera/photobasics.html

https://coderwall.com/p/3-tgjg/take-a-photo-via-adb

Or similar to this one
https://stackoverflow.com/questions/6061421/how-to-disable-search-key-and-camera-key-while-displaying-menu

I mean, an intent with this action
Android.intent.action.VOICE_COMMAND
it works

This one
android.intent.action.CAMERA_BUTTON
Doesn't work

What do you think?

I have seen in some images that Flic app should has the possibility to control the shutting command of our native camera app. In these images the app asks to choose which app you want to control.
I have a little problem, in my app (android phone), there is only the action "camera" which start an "easy" camera app and take a photo.
I need to use the native camera and simulate with the flic button, the shutter command.
Is it possible to restore this function?
Else, is it possible to use the Android Intent to send a similated "volume up push"?
I mean, for example, there is a keyevent called KEYCODE_VOLUME_UP or KEYCODE_CAMERA.
Is it possible to use this intent or maybe is there other solutions?
Thank you.