For projects that have been established, if the original project name is found to be inappropriate, if you want to completely change the project name, you need three steps:
1. Change the project name
Select the project name and right-click-->refactor-->rename.
2. Change the package name under the src file
Select the package name and change it in the same way as step 1. But notice that all the options in the pop-up box are selected, and the other items are not changed until finish.
Note: The package name can only be lowercase.
3. Change the package name under Gen file
Select the package name, change the way the package name under the step 2.gen file is usually the same as the file package name under SRC. However, you are prompted that the name already exists, regardless of the hint.
If you do not perform the third step, when you view the running program in the Application Manager, you will find that the program name is still the original name at this time.
Source: >
From for notes (Wiz)
Android Development: Change project name completely