非工作范围存储的写入权限Android SDK 30（又名Android 11）

Question

还有人发现范围存储几乎不可能工作吗？哈哈。

我一直在努力理解如何允许用户给我的应用程序写的权限，在应用程序的文件夹之外的文本文件。（假设允许用户编辑文档文件夹中的文件文本）。我已经设置了manage_external_storage权限，并且可以确认应用程序具有该权限。但每次我试着

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

“我的清单”请求以下三个权限：

<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" />

我也尝试过使用遗留存储：

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

但仍然遇到只读问题。

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)
        }

后来呢

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。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)
    }
}