In most cases you do not need c/c++ to develop for android.
According to Android NDK Overview
II. Android NDK Non-Goals: -------------------------- The NDK is *not* a good way to write generic native code that runs on Android devices. In particular, your applications should still be written in the Java programming language, handle Android system events appropriately to avoid the "Application Not Responding" dialog or deal with the Android application life-cycle. II. Android NDK Non-Goals:
The NDK is not a good way to write generic native code that runs on Android devices. In particular, your applications should still be written in the Java programming language, handle Android system events appropriately to avoid the "Application Not Responding" dialog or deal with the Android application life-cycle.
however c/c++ is important if you want to use existing c/c++ libraries.
Example: Android has no build-in mp3 encoder but you can use opensource lame library.
The same might apply to 3d-imageprocessing