is there an API or event listener or plugin or whatever means that corona can utilize android phone camera?
Yes. Check docs:
I can’t find it. can you provide the link to me? thanks
Out of the box you can call up the native camera app to capture photos, but you’re somewhat reliant on the user actually then taking a photo with it. https://docs.coronalabs.com/api/library/media/capturePhoto.html
To display the camera preview and take captures directly, without relying on user interaction, we have a plugin: https://marketplace.coronalabs.com/corona-plugins/android-custom-camera-preview
Our plugin is built in native Java so displays on top of the rest of your app, but does include the ability to display text and imagery overlaying the preview, so that you can show instructions or results to the user at the same time, or a custom cross-hair graphic. There’s no way of showing the preview behind other display objects unfortunately.
thanks to all. 
Yes. Check docs:
I can’t find it. can you provide the link to me? thanks
Out of the box you can call up the native camera app to capture photos, but you’re somewhat reliant on the user actually then taking a photo with it. https://docs.coronalabs.com/api/library/media/capturePhoto.html
To display the camera preview and take captures directly, without relying on user interaction, we have a plugin: https://marketplace.coronalabs.com/corona-plugins/android-custom-camera-preview
Our plugin is built in native Java so displays on top of the rest of your app, but does include the ability to display text and imagery overlaying the preview, so that you can show instructions or results to the user at the same time, or a custom cross-hair graphic. There’s no way of showing the preview behind other display objects unfortunately.
thanks to all.