System app with android:persistent=true crashes after update

Question

I have a system-privileged app with android:persistent=true in < application>. When I update it (via ADB or any other way), it fails to update properly and crashes.

What I'm seeing is that the system installs the update while the current (system-installed) version is still running. During the update the system does not stop the process (either attempts to stop and fails or doesn't try at all). After the update completes, the app seems to undergo a "restart" - I'm seeing components being initialized such as Application::onCreate() being called. But this is happening on same process as before the update!

Consequently (upon launching some activity of the app), the app crashes with "weird" exceptions such as failing to cast class to itself:

Caused by: java.lang.ClassCastException: com.XX.YY.ZZ.ClassName cannot be cast to com.XX.YY.ZZ.ClassName

While investigating, I saw that the ClassLoader used after the update does not refer to the the path of the updated APK, but remains pointing to the path of the original version:

Expected classloader:

dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.app.package-1/base.apk"],nativeLibraryDirectories=[/data/app/com.app.package-1/lib/x86_64, /data/app/com.app.package-1/base.apk!/lib/x86_64, /system/lib64, /vendor/lib64]]]

Actual classloader:

dalvik.system.PathClassLoader[DexPathList[[zip file "/system/priv-app/Appname.apk"],nativeLibraryDirectories=[/system/lib64/Start, /system/priv-app/Appname.apk!/lib/x86_64, /system/lib64, /vendor/lib64, /system/lib64, /vendor/lib64]]]

I'm assuming this is a result of not restarting the process during update.

Is there a way to update an app with persistent=true? Or is it an expected behavior, such app cannot be updated by the common update procedure (e.g. posting newer version on Google Play)?

Answer 1

You cannot use adb install when working with apps that are in the system image, and apps that are persistent must be in the system image. What version of Android are you developing for? On recent versions of android I use one of methods described below. Before each you must run adb remount at least once.

Method 1: Works for code changes only, does not work for resource changes or manifest changes

Temporarily add this to your Android.mk:

LOCAL_DEX_PREOPT := false # Do not commit

Then perform a build with mm or the like.

Run the appropriate push command like so:

adb push $OUT/system/priv-app/MyApp/MyApp.apk /system/priv-app/MyApp/

Because the app is persistent you must kill the app process with the following command for it to pick up the changes:

adb shell ps | grep com.my.app | awk '{print $2}' | xargs adb shell kill

Do not forget to remove or comment out the change made to Android.mk before committing or making full builds.

Method 2: Necessary for anything other than simple java code changes

Perform a build with mm or the like.

Run the following commands:

adb sync
adb shell stop
adb shell start

Method 3

Just for completeness you could just build the entire tree and either flash the system or apply an OTA from the result.