ashmem | using ashmem in Android Applications | Android library
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QUESTION
I'm building an embedded Android device and I have a Qt/QML
app I'd like to install as a system app.
However, when I attempt to launch it after moving it to /system/app
or /system/priv-app
, I get a popup box "Your application encountered a fatal error and cannot continue"
I tried this on the simplest QML project and as standard an emulator config as I could, and still ran into the issue
I'm doing this on Windows now as I write this question, but I also ran into the same issue trying to do it from my main Linux development machine.
Steps I followed leading up to this (some may be in a different order than they were actually performed, I'm recalling from memory after trial and error):
- Install Android Studio Canary (2021.1.1 Canary 7)
- Install Android 29 SDK and the x86 emulator image (Google APIs, not Google Play), create a Pixel 5 API 29 virtual device
- Install Qt 5.15.2 for Android from the Qt maintenance tool / online installer
- Install AdoptOpenJDK 8
- Run Qt Creator, head to Tools->Options->Devices->Android, point it to the AdoptOpenJDK installation, let it set up the tools it needs, and verify everything has green checkmarks
- Start a new project and select the Qt Quick "Swipe" template (bare minimum QML example), 5.15.2 for Android. Named "QMLhello" in this case.
- In "Projects" tab under the "Build" settings for 5.15.2 multi-abi, expand the "qmake" section and check the "x86" checkbox so that it builds an ABI for the Android emulator
- Verify that Qt Creator can build and run the app as a "normal" app (the green "Run" button successfully deploys and launches the app, and can swipe between pages)
Steps I performed in order to prepare to move the app to the system:
- Add environment variable
studio.emu.params
to the user environment, with the contents-writable-system
- Restart Android Studio and cold boot the AVD emulator to start with a writable system as specified in the environment variable
adb devices
lists the emulator as a deviceadb root
andadb remount
successfully remounts
What I tried after some rummaging around, combining some older answers on StackOverflow into my attempt:
...ANSWER
Answered 2021-Aug-19 at 23:20My mistake was moving the libraries to /system/lib
. I believe I may have blindly copied all the steps of a previous answer where that was necessary, and some changes in Qt and/or Android may've have happened since then that lead to my issue.
For my purposes, it was sufficient to simply move the directory altogether as-is from /data/app/
to /system/priv-app
, keeping the library subdirectory.
QUESTION
I run my Android app (based on Java), and it works. Next, I add to my app code:
FirebaseFirestore fdb = FirebaseFirestore.getInstance();
This code I got from the official Android site https://firebase.google.com/docs/firestore/quickstart
App runs, but next the running device shows the message "app has stopped".
I use a device simulator available in Android Studio.
It is my first Android app, and I can't understand what is going.
----Trace------ 2021-06-08 20:57:30.186 7155-7155/? D/AndroidRuntime: >>>>>> START com.android.internal.os.RuntimeInit uid 2000 <<<<<< 2021-06-08 20:57:30.188 7155-7155/? D/AndroidRuntime: CheckJNI is ON 2021-06-08 20:57:30.210 7155-7155/? W/art: Unexpected CPU variant for X86 using defaults: x86 2021-06-08 20:57:30.214 7155-7155/? D/ICU: No timezone override file found: /data/misc/zoneinfo/current/icu/icu_tzdata.dat 2021-06-08 20:57:30.229 7155-7155/? E/memtrack: Couldn't load memtrack module (No such file or directory) 2021-06-08 20:57:30.229 7155-7155/? E/android.os.Debug: failed to load memtrack module: -2 2021-06-08 20:57:30.230 7155-7155/? I/Radio-JNI: register_android_hardware_Radio DONE 2021-06-08 20:57:30.239 7155-7155/? D/AndroidRuntime: Calling main entry com.android.commands.am.Am
...ANSWER
Answered 2021-Jun-09 at 03:39At the end of your log, just before the initial crash. there is a warning:
Default FirebaseApp failed to initialize because no default options were found. This usually means that com.google.gms:google-services was not applied to your gradle project.
simply adding com.google.gms:google-services
should fix any issues you have, if you have issues, ensure your Gradle cache is cleared or run without the build cache
--no-build-cache
QUESTION
I am working on an application which provides set of question for practice or exam and at end of test we provide an adoption to retest your skills but whenever user refresh for a retest it shows same response as in the first attempt but if I try to fetch data from phpfile url It shows different set of data
just wondering that any cache to do with this.
just ignore the URLs because of restrictions all of them are edited
Connection File
...ANSWER
Answered 2020-Aug-28 at 08:07I am answering my own question
I just found a temporary solution but failed to find what is happening inside retrofit and android and why
QUESTION
I create an cross platform application. when run project in debug mode and click on login button it work correctly ,but when i set in release mode and click on login button get my error message this is my Login xaml
...ANSWER
Answered 2020-Jul-21 at 07:21OK, after 4 days, my resolver was change my assembly name from mixed lowercase and upercase to lowercase and every think work fine to this time.
QUESTION
I have am335x related customized board and kernel(4.4.16) source code I configure the FTDI module driver. so after kernel start successfully I attach ftdi converter to usb port and then type lsmod command to check module list
...ANSWER
Answered 2020-Jul-11 at 14:41As you can see in the dmesg output:
[ 5.379690] usb 1-1: New USB device found, idVendor=10c4, idProduct=ea60
Looking that up, e.g. here: https://www.google.com/search?q=usb%20vendor%20id%2010c4
Tells you that it's a "Silicon Labs" USB device, who also make the CP2102.
The log does not identify other devices (ignore the linux kernel root hub). So either you have also a CP2102 attached (and the FTDI is not properly connected) or the device you think is a FTDI based device, is not.
In addition you can identify currently enumerated devices using the lsusb
command.
The automatic loading is usually done by udev
or a similar user space daemon/mechanism. A decent explanation can be found e.g. here: https://lwn.net/Articles/740455/
QUESTION
I was doing my android project. Basically the user enters a text and the model predicts whether it is offensive or not. This was done by training a deep learning model LSTM on python. Then I deployed it to the cloud (Firebase). And downloaded it in my android phone and created an interpreter from the remote model if it's been downloaded. Now when I try to run the application, the model gets downloaded from the cloud but it gives an error. PFA screenshot of the error message. Let me know what am I am doing wrong and why such an error occurred?
This is the log I get when I run the application,
...ANSWER
Answered 2020-Jun-08 at 18:07It seems to be a tensorflow-lite library internal problem. Your code seems to work fine as the following statement is recorded in the log: "succed to build FirebaseModelInterpreter", which means that onSuccessListener has worked fine. The problem occurs afterwards when tensorflow lite runtime is being initialized and the error is a libc error, which seems to have originated at the OS level, apparently due to some illegal memory access. In my assessment, this can only be due to tensorflow-lite library itself. You may try with a different version of the library or a different device, but I can't say anything for sure.
In gradle file:
Try changing
implementation 'org.tensorflow:tensorflow-lite:2.0.0'
to
implementation 'org.tensorflow:tensorflow-lite:+'
QUESTION
The problem was there when I was using Fabric Crashlytics and now with Firebase Crashlytics latest version it still exists. Everything is implemented based on official NDK docs and the symbol (cSYM) files are uploaded properly after every build. I managed to produce an intentional crash to compare the tombstone and reported native crash backtrace, here is the result:
Reported crash on Firebase console:
The crash saved tombstone file:
...ANSWER
Answered 2020-May-26 at 20:26Firebaser here-
It looks like this crash report you've pasted a screenshot for is occurring in system libraries only. We can see that in the Crashlytics crash report (and the tombstone) that all the stackframes are associated with "libc.so" - this is an Android system runtime library, and any libraries like those Crashlytics is unable to symbolicate.
This is because Crashlytics can only symbolicate crashes or stackframes that come from libraries that you've uploaded symbols for. And since libc.so is a system library for which both you and Crashlytics both don't have the symbols for, this is expected behavior. Crashlytics still shows the frames even though it can't symbolicate just so that it's still reporting as much info as possible.
If you're able to submit a test crash report that has a callstack that goes through your own native libraries for which you're attempting to upload symbols, and you're still seeing "(Missing)" everywhere, that would be unexpected. If that's the case, I recommend making sure you've followed these instructions in the doc you linked, and reaching out to Firebase support if you're still having issues.
QUESTION
Android Studio 3.6
In my activity:
...ANSWER
Answered 2020-May-09 at 21:07your observable should subscribed on background thread for doing a network call. in RxJava you can use subscribeOn(Schedulers.io())
. that means your observable will be subscribed on io schedulers. io schedulers is commonly used when you are doing a network call operation
QUESTION
This is the first time I'm facing this issue, the app works all fine in the development environment. Checked the console everything works fine but when I made a release apk during the network request the app throws an error Network Error
.
ANSWER
Answered 2020-Mar-11 at 14:15In your androidManifest.xml try this :
QUESTION
Library written in c++ produces continuous stream of data and same has to be ported on different platforms. Now integrating the lib to android application, I am trying to create shared memory between NDK and SDK.
Below is working snippet,
Native code:
...ANSWER
Answered 2020-Feb-20 at 09:49You only need /dev/ashmem
to share memory between processes. NDK and SDK (Java/Kotlin) work in same Linux process and have full access to same memory space.
The usual way to define memory that can be used both from C++ and Java is by creating a Direct ByteBuffer. You don't need JNI for that, Java API has ByteBuffer.allocateDirect(int capacity). If it's more natural for your logical flow to allocate the buffer on the C++ side, JNI has the NewDirectByteBuffer(JNIEnv* env, void* address, jlong capacity) function that you used in your question.
Working with Direct ByteBuffer is very easy on the C++ side, but not so efficient on the JVM side. The reason is that this buffer is not backed by array, and the only API you have involves ByteBuffer.get() with typed variations (getting byte array, char, int, …). You have control of current position in the buffer, but working this way requires certain discipline: every get() operation updates the current position. Also, random access to this buffer is rather slow, because it involves calling both positioning and get APIs. Therefore, in some cases of non-trivial data structures, it may be easier to write your custom access code in C++ and have 'intelligent' getters called through JNI.
It's important not to forget to set ByteBuffer.order(ByteOrder.nativeOrder()). The order of a newly-created byte buffer is counterintuitively BIG_ENDIAN. This applies both to buffer created from Java and from C++.
If you can isolate the instances when C++ needs access to such shared memory, and don't really need it to be pinned all the time, it's worth to consider working with byte array. In Java, you have more efficient random access. On the NDK side, you will call GetByteArrayElements() or GetPrimitiveArrayCritical(). The latter is more efficient, but its use imposes restrictions on what Java functions you can call until the array is released. On Android, both methods don't involve memory allocation and copy (with no official guarantee, though). Even though C++ side uses the same memory as Java, your JNI code must call the appropriate Release…() function, and better do that as early as possible. It's a good practice to handle this Get/Release via RAII.
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Install ashmem
You can use ashmem like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the ashmem component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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