Heat up the camera glass for a while. You can use a hair dryer instead of heat gun. Scotch tape. Put some tape around the camera lens. Prevent from scratching the back cover. Now we can remove the broken camera glass.
And you need a tweezers. A black adhesive around the glass. We need to loosen it up. Be careful. Do not scratch the rear camera.
Keep pry up the glass. The glass is removed. Some small detritus on the camera here. Take up the device cautiously and flap the small detritus away. Use a Band-aid stick the detritus left away.
A cotton swab. You can also put some alcohol for cleaning. Heat up the glass. A regular pen. Use a pen to pop out the glass.
This way can be safety for rear camera. But need to remove the rear housing. Here is the camera glass. In this video,I use a Samsung S7 camera glass instead. The side which comes with black masklike is inside.
The new product must come with sticker. S7's glass is a little bit big. But applicable if installed carefully. Recommend for an original camera glass for OnePlus 3. The link is in the description.
The glass installation need to be very careful. If not,it will broken like this. Camera glass installation like the video showed. Do not put more pressure in the middle of the glass. Install it from the edges of the glass instead.
Strongly recommend for an original camera glass of OnePlus 3 again. You can get it in the description. The S7's camera glass is a relatively thiner than OnePlus's.
Source : Wit Rigs