Despite most android applications is developed using java and kotlin programming languages (in the android studio,) the development of the operating system itself still happens through c and c+. Google however recognized that there is a limitation in this: from now on, the development of android in the aosp project can take place in c, c+ and rust. Low level development of the android operating system requires system programming languages such as c and c ++.
Unfortunately, c and c+ fail to provide security of memory, making them subject to bugs and security vulnerabilities. C and c+ together constitute tens of millions of lines of code on the android platform. These memory security bugs become the most difficult code incorrect source to deal with, representing about 70% of android high gravity security vulnerabilities.
By contrast, rust provides security of memory using a combination of check-up and runtime to ensure that memory access is valid. Although rust actually has its advantages, it is not possible to pass from today to tomorrow the entire android operating system to rust. Google believes that its efforts for a secure development language for memory are better focused on novelties than on rewriting code c and c+ mature.
Although it is not related to android, we point out that also the new fuchsia netstack was written in rust.