Find another messaging app. The inability to disable the camera preview when the attached menu is open is absolutely unacceptable. If you want to prevent the camera from launching  wasting battery  and crashing older devices  you'll have to disable it in the system permission menu (but only newer versions of Android support that  meaning old devices are still losing battery and crashing because of this offensively obvious bug that they refuse to repair). Find yourself a messaging app that supports  instead of ignores  its community.
January 08 2017