hi all! how can I avoid Android to request the permissions again when the phone is rotated?

# android

[Manuel Lorenzo]

hi all!

how can I avoid Android to request the permissions again when the phone is rotated?

[Manuel Lorenzo]

for example in my MainActivity I have this:

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            PSPDFKitAssignmentTheme {
                MainScreen()
            }
        }
    }

    @OptIn(ExperimentalAnimationApi::class)
    @SuppressLint("UnusedMaterialScaffoldPaddingParameter")
    @Composable
    fun MainScreen(
        mainViewModel: MainViewModel = viewModel(),
        savePDFViewModel: SavePDFViewModel = viewModel()
    ) {
        val navController = rememberAnimatedNavController()
        val navBackStackEntry by navController.currentBackStackEntryAsState()

        if (ActivityCompat.checkSelfPermission(
                this,
                Manifest.permission.MANAGE_EXTERNAL_STORAGE
            ) == PackageManager.PERMISSION_GRANTED
        ) {
            OpenDownloadsFolderAsLaunchedEffect()
        } else {
            RequestPermissions()
        }
        Scaffold(...

But the problem is that of course, when I rotate the device, the activity gets recreated again and if the permissions are already granted the method OpenDownloadsFolderAsLaunchedEffect() is called again and that breaks the app

[Jan Starczewski]

@Manuel Lorenzo Hi, can you show the implementation of OpenDownloadsFolderAsLaunchedEffect ?

[Manuel Lorenzo]

LaunchedEffect(true) {
    mainViewModel.openFolder(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS))
}

[Manuel Lorenzo]

@Jan Starczewski

[Jan Starczewski]

oh well sorry

[Jan Starczewski]

so

[Manuel Lorenzo]

no worries, thanks for the help by the way 🙂

[Jan Starczewski]

@Manuel Lorenzo 1. Long story short effects do not survive configuration changes and after the change they will be relaunched, what you can do to quickly fix the issue is to save state of a boolean indicating whether you made a certain job inside effect or not with rememverSaveable so It will not be launched on configuration change

val wasLaunched = rememberSaveable { mutableStateOf(false) }
            if (wasLaunched.value.not()) {
                LaunchedEffect(Unit) {
                    // do your calls
                    // mainViewModel.openFolder(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS))
                    // change value
                    wasLaunched.value = true
                }
            }

[Jan Starczewski]

2. Other solution is to move the state into viewModel assuming it is properly scoped, so I also survives configuration changes, and then you can relay on the value of it to launch an effect or not

[Manuel Lorenzo]

and how can I move it there? I’ve been trying to find out how to handle the permissions there but I can’t find any example

[Jan Starczewski]

What do you mean by “how can I move it there”?

[Manuel Lorenzo]

how to handle the permissions in the view model

[Jan Starczewski]

Do not handle permission in the view model, just keep some kind of information (state) that you have already handled it inside view or not

[Jan Starczewski]

I can try to provide a full example, but just give me some time

[Manuel Lorenzo]

oh OK thanks!

[Jan Starczewski]

@Manuel Lorenzo but I am wondering, you are asking how to keep the state in ViewModel, or how to handle permissions?

[Manuel Lorenzo]

to be honest, I have a huge mess here, and in particular two problems:
• I need to show a list of downloaded PDFs, and I need to request the permissions based on the API level. When the permissions are granted and I get back to my app’s screen, the documents aren’t there so I need to close and open the app again.
• When I have my app and I rotate the OpenDownloadsFolderAsLaunchedEffect is called again, which kind of restarts the data structure that holds the list of documents of the app, and thus the state isn’t saved

[Jan Starczewski]

Allright, and when you get back to the app it crashes?

[Manuel Lorenzo]

no, it just doesn’t show anything

[Jan Starczewski]

right, so as I understand the problem is only the fact that the folder is being opened twice as you mentioned, yes?

[Jan Starczewski]

because of the second launch

[Manuel Lorenzo]

yeah, I would consider the second problem the most important one actually

[Manuel Lorenzo]

@Composable
    fun MainScreen(
        mainViewModel: MainViewModel = viewModel(),
        savePDFViewModel: SavePDFViewModel = viewModel()
    ) {
        val navController = rememberAnimatedNavController()
        val navBackStackEntry by navController.currentBackStackEntryAsState()

        if (ActivityCompat.checkSelfPermission(
                this,
                Manifest.permission.MANAGE_EXTERNAL_STORAGE
            ) == PackageManager.PERMISSION_GRANTED
        ) {
            OpenDownloadsFolderAsLaunchedEffect()
        } else {
            RequestPermissions()
        }
        Scaffold(...

As you can see here it’s my MainScreen and of course, when rotated the checkSelfPermission is called again because the activity was rotated

[Manuel Lorenzo]

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            PSPDFKitAssignmentTheme {
                MainScreen()
            }
        }
    }

Not the best way I guess

[Jan Starczewski]

So as I said, you can prevent the launch with saved value by rememberSaveable but to be honest it that case it may not be the best thing to do, because after process death when app is opened again it will prevent downloading the pdfs, I think we should go with viewModel approach

[Jan Starczewski]

Could you please send me the impl of openFolder function ?

[Manuel Lorenzo]

fun openFolder(selectedItem: File) {
        viewModelScope.launch(ioDispatcher) {
            val filesList = getFilesList(selectedItem)
            _documentListLiveData.postValue(buildDocumentListToShow(selectedItem, filesList))
        }
    }

[Jan Starczewski]

I think the easiest solution for you is to check whether your files represented by _documentListLiveData is has an empty value before downloading it with getFilesList or expose other live data like canOpenFolder that can represent the state informing whether you should open the folder or not.

@Composable
fun OpenDownloadsFolderAsLaunchedEffectIfClosed(isClosed: Boolean) {
    if (isClosed) {
        LaunchedEffect(Unit) {
            // do your calls
            // mainViewModel.openFolder(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS))
        }
    }
}

And as the value of isClosed use the value stored in your viewModel

[Jan Starczewski]

@Manuel Lorenzo But it all depends on you what you try to achieve, adding a simple check whether opening a folder is necessary would fix the issue with your crash on configuration change, because the viewModel will survive it and I it wont survive process death, so your folder then will be opened again assuming that’s the behaviour you want

[Manuel Lorenzo]

that’s true indeed

[Manuel Lorenzo]

thanks a lot for your help @Jan Starczewski