Android 11：保存其他应用可以访问的文件

Question

(This question is regarding Android 11)

I want to print crash logs to a file that other applications can read (specifically, I want to be able to navigate to the file and view the data with the "Files" app).

I've seen dozens of answers to this question, but they all have one of two problems:

1. they're using Environment.getExternalStoragePublicDirectory which is deprecated, or
2. they're using getExternalFilesDir but this returns a directory that is not visible to other apps.

Please note I want to do this in my Application class, not in an activity.

According to the official docs I could save it as a "document", but the example provided there has a problem; it is invoked from an activity. Since I am trying to invoke it from an application, the method startActivityForResult doesn't exist.

// Request code for creating a PDF document.
const val CREATE_FILE = 1

private fun createFile(pickerInitialUri: Uri) {
    val intent = Intent(Intent.ACTION_CREATE_DOCUMENT).apply {
        addCategory(Intent.CATEGORY_OPENABLE)
        type = "application/pdf"
        putExtra(Intent.EXTRA_TITLE, "invoice.pdf")

        // Optionally, specify a URI for the directory that should be opened in
        // the system file picker before your app creates the document.
        putExtra(DocumentsContract.EXTRA_INITIAL_URI, pickerInitialUri)
    }
    startActivityForResult(intent, CREATE_FILE) // <--- This does not compile, a subclass of Application doesn't have this method avaiable...
}

Answer 1

For Android 11. In your case, I think contentResolver.insert will be more suitable.

You'll need to use MediaStore.Files.getContentUri & put your content values in it. Then write your crash log to it by using openOutputStream & outputStream.write .

This can be used in the Application class as well.

Following is the code snippet tested on Android 11.

class MyApp : Application() {

    override fun onCreate() {
        super.onCreate()
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            saveFileToExternalStorage(
                System.currentTimeMillis().toString(),
                "This is test crash log"
            )
        } else {
            //your old code for below Q
        }
    }

    @RequiresApi(Build.VERSION_CODES.Q)
    private fun saveFileToExternalStorage(displayName: String, content: String): Boolean {
        val externalUri = MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)

        val relativeLocation = Environment.DIRECTORY_DOCUMENTS

        val contentValues = ContentValues().apply {
            put(MediaStore.Files.FileColumns.DISPLAY_NAME, "$displayName.txt")
            put(MediaStore.Files.FileColumns.MIME_TYPE, "application/text")
            put(MediaStore.Files.FileColumns.TITLE, "Log")
            put(MediaStore.Files.FileColumns.DATE_ADDED, System.currentTimeMillis() / 1000)
            put(MediaStore.Files.FileColumns.RELATIVE_PATH, relativeLocation)
            put(MediaStore.Files.FileColumns.DATE_TAKEN, System.currentTimeMillis())
        }


        return try {
            contentResolver.insert(externalUri, contentValues)?.also { uri ->
                contentResolver.openOutputStream(uri).use { outputStream ->
                    outputStream?.let {
                        outputStream.write(content.toByteArray())
                        outputStream.close()
                    }
                }
            } ?: throw IOException("Couldn't create MediaStore entry")
            true
        } catch (e: IOException) {
            e.printStackTrace()
            false
        }
    }
}

I got this idea from this github project. I would suggest you check it out too. https://github.com/philipplackner/AndroidStorage

Answer 2

Your own first suggestion was Environment.getExternalStoragePublicDirectory . If you go to the documentation , it indeed days it is deprecated and redirects you to Content. getExternalFilesDir() . This contains example code how to save data and get permission.

Although your pick was a document from the data storage docs , this is not suitable for you: every time yo want to save a log, your user is presented a save file dialog. That is way the function is called startActivityForResult , because it starts a new activity. That is also why it should be called from an existing activity, so the user is in a UI flow already and it may expect a new screen.

You need write permission, because you want to write a file without consent per file; which is considered potentially dangerous. The data storage docs says you don't need permission, because it's the new activity that already owns the permission and the user can pick a single file to be written, making it less dangerous.

Also, not all users will grant the permission. A better alternative would be is to store the crashes locally and use startActivityForResult() eventually to make it public.

Answer 3

You should convert your string to byte array and write them in loop

val sdcard = Environment.getExternalStorageDirectory()
val file = File(sdcard, "filename")
val fis = FileOutputStream(file)
fis.write("bytes", 0, count)
fis.close()

Answer 4

In Android 11 API 30 you need to grant this permission in manifest to be able to write or create new File/Folder in any location:

<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

then in your code on you MainActivity onCreate:

if (Environment.isExternalStorageManager()) {
//todo when permission is granted
} else {
//request for the permission
    Intent intent = new 
Intent(Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION);
Uri uri = Uri.fromParts("package", getPackageName(), null);
intent.setData(uri);
startActivity(intent);
}

This is Java code but you can get its Kotlin equvelant

Update

Maybe this is the Kotlin Version

    if (Environment.isExternalStorageManager()) {
        //todo when permission is granted
    } else {
        //request for the permission
        val intent = Intent(Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION)
        val uri: Uri = Uri.fromParts("package", packageName, null)
        intent.data = uri
        startActivity(intent)
    }