Lab – System Application

1. Create an android studio project with simple activity
2. Design:
   1. add Edittext, button and textview
   2. Change the layout to LinearLayout with vertical orientation 
3.   Code
   1. Change the superclass to Activity
   2. Implement the button click event – read the text in the edittext control, convert to uppercase and write to the textview control
4. Build and run on the emulator 

 

Add the application to AOSP 

•  Create a folder “app” in ~/aosp/device/generic/goldfish
• Add the following Android.mk file

include $(call all-subdir-makefiles)

• Create a new directory “sysapp” in the folder app for the system application 
• Copy the files from the android studio project to the new folder:

 

cp ~/AndroidStudioProjects/SysApp/app/src/main/* -r .

• Add the following Android.mk file to sysapp folder:

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := eng
LOCAL_SRC_FILES := $(call all-java-files-under,java)
LOCAL_PACKAGE_NAME := sysapp
include $(BUILD_PACKAGE)

• Use mm to build the code – remove styles to make it compiled 
• build the emulator and test your work 

Make Your Application Run with System Privileges

Add coreApp and sharedUserId to the manifest file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="app.mabel.com.jnitest"
        coreApp="true"
        android:sharedUserId="android.uid.system">
....


</manifest>

Add the following vars to main Android.mk file:

LOCAL_CERTIFICATE := platform
LOCAL_PRIVILEGED_MODULE := true

Build the rom and test your work

Now run the application, connect to the device using adb and run ps -A to see all the processes. You will see application run as system user