Android Crash | `filesystem error: Permission Denied`

[ProgrammedForAdventure]

The latest version (3.9.0) of MAVSDK-Java causes a native crash on Android, the primary error message being:
filesystem_error: filesystem error: in create_directory: Permission denied [/data/local/tmp/mavsdk-component-metadata-a4dc8fef]

The issue does not appear on version 3.6.0. I tried granting Android additional permissions, but this did not solve the issue. I am pretty confident the mentioned path (/data/local/tmp) is a restricted location on Android, that could only be written to on a rooted device.

2025-08-04 13:14:13.991 15460-15753 MAVSDK-Server            D  Running mavsdk_server with connection url: udpout://<drone_ip>:14550
2025-08-04 13:14:13.991 15460-15753 Mavsdk                   I  Waiting to discover system on udpout://<drone_ip>:14550...
2025-08-04 13:15:27.158 15460-15756 Mavsdk                   D  New system ID: 1 Comp ID: 1
2025-08-04 13:15:27.162 15460-15756 libc++abi                E  terminating with uncaught exception of type std::__ndk1::__fs::filesystem::filesystem_error: filesystem error: in create_directory: Permission denied [/data/local/tmp/mavsdk-component-metadata-a4dc8fef]
2025-08-04 13:15:27.186 15460-15756 libc                     A  Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 15756 (mavsdk-event-qu), pid 15460 (myapp)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A  Cmdline: myapp
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A  pid: 15460, tid: 15756, name: mavsdk-event-qu  >>> myapp <<<
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #01 pc 00000000000d1fcc  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #02 pc 00000000000d2180  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #03 pc 00000000000e6e80  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #04 pc 00000000000e6514  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #05 pc 00000000000e646c  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (__cxa_throw+124) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #06 pc 000000000007cbb4  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #07 pc 000000000007fc54  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #08 pc 00000000000803f0  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libc++_shared.so (offset 0x20c8000) (std::__ndk1::__fs::filesystem::__create_directory(std::__ndk1::__fs::filesystem::path const&, std::__ndk1::error_code*)+140) (BuildId: df3f83af4e54f316c793c3655c4753a8851a234c)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #09 pc 00000000017f9224  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::create_tmp_directory(std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&)+656)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #10 pc 00000000017e56c8  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::MavlinkComponentMetadata::MavlinkComponentMetadata(mavsdk::SystemImpl&)+1144)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #11 pc 00000000017bff5c  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::SystemImpl::SystemImpl(mavsdk::MavsdkImpl&)+612)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #12 pc 00000000017bfb84  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::System::System(mavsdk::MavsdkImpl&)+68)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #13 pc 00000000017d285c  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::MavsdkImpl::make_system_with_component(unsigned char, unsigned char)+632)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #14 pc 00000000017d19b0  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::MavsdkImpl::process_message(__mavlink_message&, mavsdk::Connection*)+2688)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #15 pc 00000000017d0ec4  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::MavsdkImpl::process_messages()+112)
2025-08-04 13:15:27.432 15899-15899 DEBUG                    A        #16 pc 00000000017cef4c  /data/app/~~XODcxK6cmAIVh-OPmfQN-g==/myapp-YIgzs15ssLvXR7zzlCwbYg==/base.apk!libmavsdk_server.so (offset 0xaf38000) (mavsdk::MavsdkImpl::work_thread()+108)

[JonasVautherin]

Yes, /data/local/tmp will probably never work on modern Android. So you should probably set the path manually.

I am not sure where this is used: are you saying that you don't need it at all and shouldn't have to set the path manually? Because I guess it wasn't writing a file before 3.6.0 anyway 🤔.

@julianoes: is this a path that could be made optional instead of hardcoded to /data/local/tmp?

[ProgrammedForAdventure]

I did not make any changes to my code when upgrading versions, it just crashes when trying to run mavSdkServer.run(systemAddress) and a Mavlink connection is initially established. I don't know what the tmp directory is being used for; I don't explicitly need it for my purposes.

I saw something about "configurable temp directory" in version 3.8.1's notes?

[ProgrammedForAdventure]

I see there is a new setTempDirectory() command like you mentioned -- is there something I should throw in here for now as a workaround? I didn't know it existed.

[matthieu-db]

Same behavior here, I fixed it with mavsdkServer.setTempDirectory(applicationContext.cacheDir.absolutePath)

[ProgrammedForAdventure]

Great, thanks! Might be worth fixing or adding a line to the README for setup guidelines if this is expected.

[JonasVautherin]

I think a fix would have to go on the C++ side (the part that uses the value set by setTempDirectory(). Ideally it would make it optional to call setTempDirectory(), so that if you don't actually need it you don't have to set it at all.

[ProgrammedForAdventure]

I can confirm that using mavsdkServer.setTempDirectory(applicationContext.cacheDir.absolutePath) is a valid workaround for this issue.

[JonasVautherin]

I think it's not ideal to crash by default. Trying to improve it here.

@matthieu-db, @ProgrammedForAdventure: Would you be willing to try it and review the PR? I published 3.10.0-3-SNAPSHOT (see the docs for the SNAPSHOTs here).

[ProgrammedForAdventure]

Thanks @JonasVautherin! I was slow to getting to this, looks like you've got it resolved now 🙌