android - 写入权限不起作用 - 范围存储 Android SDK 30(又名 Android 11)

Question

还有其他人发现分区存储几乎无法工作吗？哈哈。

我一直在尝试了解如何允许用户向我的应用授予对应用文件夹外的文本文件的写入权限。 (假设允许用户编辑其文档文件夹中文件的文本)。我设置了 MANAGE_EXTERNAL_STORAGE 权限，可以确认该应用程序拥有该权限。但还是每次我尝试

val fileDescriptor = context.contentResolver.openFileDescriptor(uri, "rwt")?.fileDescriptor

我收到Illegal Argument: Media is read-only 错误。

我的 list 请求这三个权限:

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

我也尝试过使用传统存储:

<application
    android:allowBackup="true"
    android:requestLegacyExternalStorage="true"

但仍然遇到这个只读问题。

我错过了什么？

额外说明

我如何获取 URI:

view?.selectFileButton?.setOnClickListener {
            val intent =
                Intent(Intent.ACTION_OPEN_DOCUMENT).apply {
                    addCategory(Intent.CATEGORY_OPENABLE)
                    type = "*/*"
                    flags = Intent.FLAG_GRANT_READ_URI_PERMISSION or
                            Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                }
            startActivityForResult(Intent.createChooser(intent, "Select a file"), 111)
        }

然后

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (requestCode == 111 && resultCode == AppCompatActivity.RESULT_OK && data != null) {
        val selectedFileUri = data.data;
        if (selectedFileUri != null) {
            viewModel.saveFilename(selectedFileUri.toString())
            val contentResolver = context!!.contentResolver
            val takeFlags: Int = Intent.FLAG_GRANT_READ_URI_PERMISSION or
                    Intent.FLAG_GRANT_WRITE_URI_PERMISSION
            contentResolver.takePersistableUriPermission(selectedFileUri, takeFlags)
            view?.fileName?.text = viewModel.filename
            //TODO("if we didn't get the permissions we needed, ask for permission or have the user select a different file")
        }
    }
}

Answer 1

您可以试试下面的代码。它对我有用。

class MainActivity : AppCompatActivity() {

    private lateinit var theTextOfFile: TextView
    private lateinit var inputText: EditText
    private lateinit var saveBtn: Button
    private lateinit var readBtn: Button
    private lateinit var deleteBtn: Button

    private lateinit var someText: String
    private val filename = "theFile.txt"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        if (!isPermissionGranted()) {
            val permissions = arrayOf(WRITE_EXTERNAL_STORAGE)
            for (i in permissions.indices) {
                requestPermission(permissions[i], i)
            }
        }

        theTextOfFile = findViewById(R.id.theTextOfFile)
        inputText = findViewById(R.id.inputText)
        saveBtn = findViewById(R.id.saveBtn)
        readBtn = findViewById(R.id.readBtn)
        deleteBtn = findViewById(R.id.deleteBtn)

        saveBtn.setOnClickListener { savingFunction() }
        deleteBtn.setOnClickListener { deleteFunction() }
        readBtn.setOnClickListener {
            theTextOfFile.text = readFile()
        }

    }

    private fun readFile() : String{
        val rootPath = "/storage/emulated/0/Download/"
        val myFile = File(rootPath, filename)
        return if (myFile.exists()) {
            FileInputStream(myFile).bufferedReader().use { it.readText() }
        }
        else "no file"
    }

    private fun deleteFunction(){
        val rootPath = "/storage/emulated/0/Download/"
        val myFile = File(rootPath, filename)
        if (myFile.exists()) {
            myFile.delete()
        }
    }

    private fun savingFunction(){
        deleteFunction()
        someText = inputText.text.toString()
        val resolver = applicationContext.contentResolver
        val values = ContentValues()
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.Q) {
            values.put(MediaStore.MediaColumns.DISPLAY_NAME, filename)
            values.put(MediaStore.MediaColumns.MIME_TYPE, "text/plain")
            values.put(MediaStore.MediaColumns.RELATIVE_PATH, Environment.DIRECTORY_DOWNLOADS)
            val uri = resolver.insert(MediaStore.Files.getContentUri("external"), values)
            uri?.let { it ->
                resolver.openOutputStream(it).use {
                    // Write file
                    it?.write(someText.toByteArray(Charset.defaultCharset()))
                    it?.close()
                }
            }
        } else {
            val rootPath = "/storage/emulated/0/Download/"
            val myFile = File(rootPath, filename)
            val outputStream: FileOutputStream
            try {
                if (myFile.createNewFile()) {
                    outputStream = FileOutputStream(myFile, true)
                    outputStream.write(someText.toByteArray())
                    outputStream.flush()
                    outputStream.close()
                }
            } catch (e: Exception) {
                e.printStackTrace()
            }

        }
    }

    private fun isPermissionGranted(): Boolean {
        val permissionCheck = ActivityCompat.checkSelfPermission(this, WRITE_EXTERNAL_STORAGE)
        return permissionCheck == PackageManager.PERMISSION_GRANTED
    }

    private fun requestPermission(permission: String, requestCode: Int) {
        ActivityCompat.requestPermissions(this, arrayOf(permission), requestCode)
    }
}