Develop Reference

In android, how to access file in assets or raw in c++ via url?

I want to use the url of the files in assets or raw in C++ (JNI).
However, I don't know how to obtain the url of these files, since I cann't use getAssets().open() in C++ code.

it is possible to load a C++ file from a URL and load it in android
but it's illegal and google play doesn't let apps load codes dynamically in the google play store
first you should create a new android-ndk project with the same package name
then run
./ndk build
in the intermediate folder you will get .so files which are compiled files from c++
put files for x86, x64 , arm64, x86_64, or other ABIs files in your main project or serve it in the cloud server
you can download it in phone storage
add "lib" before SO file name and add the .so extension
EXAMPLE -> libexample. so
simply call
static {
System.load("PATH_TO_THE_FILE/libfile.so");
}
or call loading from ndk with
dlopen("PATH_TO_THE_FILE/libfile.so")

Include files with different prefixes in apk

I have a project with native libraries that I want to use, files with this format: lib<name>.so do get included into apk. But files with <name>.so format does not.
Is there a way to include the later type into apk in lib directory?
If not, is there a way to include the files into a directory inside apk, where I can load it from my native code?

The short answer is "no". The native binaries will only be packed into APK, and extracted to executable files upon installation, if their names follow the lib….so pattern.
Note that these libraries will be extracted to files according to the ABI of the target system. The installer does not check the actual properties of the file. The decision is based on the name of the folder under lib in the APK structure.
If you add the attribute extractNativeLibs=false to the application tag in AndroidManifest.xml of your APK, the installer (on Android Nougat and higher) will not extract the native libraries.
You can trick the system and have files that don't follow the above rule to the lib folder of APK, but there is very little sense in it, because they will never be extracted by the loader (it may also extract file gdbserver if the file is there).
The common practice is to put the arbitrary files in the assets folder of your APK, and extract them programmatically when the app runs for the first time after install. You cannot extract these files to the secured location where the usual native libraries go. You should not extract the native libraries to sdcard (e.g. getExternalFilesDir()), because the system may not allow execution of the files there, regardless of the execute access flag on the file. Make sure that you use the correct ABI flavour.
You can peek at the source code of Nougat native lib loader that can load native libraries from the APK without extraction, and use it to load your custom libraries directly from the assets folder of your APK.

Android how to extract *.so file during execution

I have one android myLibrary.jar file. But myLibrary.jar file will load the native 3 different so file. I have a.so, b.so and c.so.
When i using in my own application, it just simply put the jar file to the Android Dependencies and all 3 so files put in the libs/armeabi of the main application package.
When deploy and install on the device, these so file will be in the data/data/my-appname/lib/*.so.
Now i need to provide the sdk solution. The user side doesn't want the main application. They just want the myLibrary.jar. So i am considering about packing all 3 *.so files to the jar. I searched for the how to add to the so files to myLibrary.jar. But i still don't understand.
In this following post:
[Ant]How to add .so file into a jar and use it within jar(set the java.library.path)?
It mentioned about adding the so file to the jar and extract at runtime. But i still don't understand how to achieve that.
After trying that mentioned in the following post:
Creating a product SDK: How do I add a native lib (.so) and a jar with the SDK I am creating?
After my sample application reference the the compiled jar that included the .so file. After installing to the device, the libs/armeabi/xxx is not unpacked on the install. So i would like to know how to extract them dynamically and save them to data/data/my-appname/lib/ so that i can use with System.loadlibary(.so).
Thanks a lot.

Using resource files in NDK

I have an NDK library that I am creating that needs to contain and access a binary data file (.dat extension). I am having trouble getting the compiled library to see this file. To make things a little more difficult, I am doing this within a library package.
I think it would work if, during my Android.mk file, I copy this .dat file to my app's resources folder, and then access that from within the app, but I feel like there must be a better way.
Any suggestions?

Instead of resources, put it in the assets folder; NDK provides API to access assets from native code.
Often, we unpack some "files" from the resources or assets to the file system (e.g. /sdcard) on the first run of the app after install. This approach works best when the files must be used by external apps and libs (e.g. to play sounds), or when these files will be changing.
Finally, you can link the data into your .so during ndk-build. This will resolve the question how the .dat file will be copied into the app folder, but reading it may be tricky, and modifying - impossible. You don't need to create a huge library. You can create a mock-up library that contains the data. If I understand correctly, you can ignore the file structure, headers, etc. You only need a file named lib something .so in your libs/armeabi (or other) folder.

Separate .so libraries from .apk

I have an enterprise app which I am deploying manually (no Google Play) which uses a number of .so libraries for mapping (ArcGIS). However, the .so files (arm, armv7a, x86) in the libs folder blow the .apk size out from 3mb to 21mb. I dont particularly want to remove one of the .so files (removing support for that architecture), or mess around with one .apk per architecture.
Can anyone think of a way I can update my app without including the .so files in each update .apk?

Yes, you can have the Java portion of your app manually download the appropriate .so files into your app's internal storage folder and mark them executable.
You will then have to load them with System.load() and the full pathname of the .so file, rather than System.loadLibrary() and the trimmed library name.
The biggest issue here is that you are now responsible for matching the ABI's yourself, and more importantly, providing your own protection against being tricked into installing a modified or imposter library which might do something nefarious in the name of your app and using it's permissions.
Of course you have to make sure not to try to call any of the native methods before you have installed them.
You could also consider delivering the .so files as binary assets each in its own skeleton .apk having a shared user id (and matching certificate) as your main .apk
Or you could simply make platform-specific .apk's for each target, containing only one .so, and have your distribution system pick the right ones (though that doesn't help with the upgrade problem).