File cannot be updated in external storage

Question

I have a file in storage and I'm trying to write data into that file. But an exception os thrown.

val file = File(myFilePath)
val data : String = my_data
var bW: BufferedWriter
try {
    bW = BufferedWriter(FileWriter(file, true));
    bW.write(data);
    bW.newLine();
    bW.flush();
    bW.close();
} catch (e: Exception) {
    Log.d("log", "error = $e")
}

The error I'm getting

java.io.FileNotFoundException: /storage/emulated/0/Download/myFolder/myFile.txt: open failed: EACCES (Permission denied)

I have placed the file in above path and I cross checked frequently that the file exists there. But why I'm getting FileNotFoundException I don't know.

My Android version is 10 QP1A and mobile I'm using redmi note 8 pro.

I tried all solutions that exists (5 to 8 years old) and nothing was working.

Answer 1

For API 29 (Android 10),

1. Ensure you have android.permission.WRITE_EXTERNAL_STORAGE granted.

2. Add android:requestLegacyExternalStorage="true" to your application element in your manifest file. Reference

E.g.

AndroidManifest.xml

<manifest ...>

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

    <application
        ...
        android:requestLegacyExternalStorage="true">
        ...
    </application>

</manifest>

MyActivity.kt

...

        val permissionStatus = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
        if(permissionStatus == PackageManager.PERMISSION_GRANTED) {
            lifecycleScope.launch(Dispatchers.IO) {
                writeToFile()
            }
        } else {
            ActivityCompat.requestPermissions(this@MainActivity,
                arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE),
                PERMISSION_REQUEST_CODE)
        }

...

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)

        if(grantResults.all { it == PackageManager.PERMISSION_GRANTED }) {
            lifecycleScope.launch(Dispatchers.IO) {
                writeToFile()
            }
        }
    }

...

    @WorkerThread
    private fun writeToFile() {
        val file = File(<myFilePath>)
        val data = <my_data>

        with(BufferedWriter(FileWriter(file, true))) {
            write(data)
            newLine()
            flush()
            close()
        }
    }
}