Android smartphone is one of the most popular smartphone operating system beside iOS, one of the common problem is unable to connect to the camera, this happened because of several reason. 90% of chance that you can fix the Can't Connect To The Camera problem yourself, my solution is using an Apps.
We will need to download apps from Google Play. Search for "Camera fix", the apps that work with my smartphone is "Camera (CMFix) for Cyanogenmod". It's free apps developed by The Seven Media Group. What this apps do is it will restart your camera hardware if it crash. So you don't have to reboot your smartphone.
Your smartphone will warn about this apps might damage your phone but simply ignore it and install anyway. The application size is less than 1MB,
Launch the camera, if error Can't Connect To The Camera appear, close it. Launch Camera (CMFix), it will not display anything. Now go back to camera and launch it. You should able to use the smartphone camera right now. This method works with most of smartphone brand such as acer, alcatel, allview, archos, asus, blu, celkon, dell, gfive, gigabyte, gionee, hp, htc, huawei, Icemobile, intex, karbonn, kyocera, lava, lenovo, lg, maximus, maxwest, micromax, Meizu, Motorola, NIU, oppo, orange, qmobile, panasonic, Philips, Plum, Prestigio, samsung, Sony, spice, symphony, toshiba, unnecto, verykool, Vivo, walton, wiko, xiaomi, xolo, yezz, zte, Zync.