How can an App write and read file in Documents folder? - android-studio

Question

I wrote an App, in Kotlin with Android Studio that write some strings to a file.
All work, I can write and read inside the App, but I can't see the file looking in Documents folder.
How can I use the folder Documents as a storage space?
Thank you
These are the function I use:
fun saveTextFile(view: View, nomeFile: String, testo: String, contesto: Context){
var fileStream: FileOutputStream
try {
fileStream = contesto.openFileOutput(nomeFile, MODE_APPEND) // OK esegue append
fileStream.write(testo.toByteArray())
fileStream.close()
}catch (e: Exception){
e.printStackTrace()
}
}
fun readTextFile(view: View, nomeFile: String, contesto: Context): String{
var fileInputStream: FileInputStream? = null
fileInputStream = contesto.openFileInput(nomeFile)
var inputStreamReader: InputStreamReader = InputStreamReader(fileInputStream)
val bufferedReader: BufferedReader = BufferedReader(inputStreamReader)
val stringBuilder: StringBuilder = StringBuilder()
var text: String? = null
while ({ text = bufferedReader.readLine(); text }() != null) {
stringBuilder.append(text)
}
inputStreamReader.close();
return(stringBuilder.toString())
}
Thank you, Livio

Answer 1

For writing in Documents folder of your device , you just need to make use of MediaStore for the same. You can take input for this function anything that you want like String , bitmap , PdfDocument and other's too .
For Your UseCase you can do the following ,
Global Variable :
private var imageUri: Uri? = null
override suspend fun saveDocument(context : Context, text : String) {
withContext(Dispatchers.IO) {
try {
val collection =
MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
val dirDest = File(
Environment.DIRECTORY_DOCUMENTS,
context.getString(R.string.app_name)
)
val date = System.currentTimeMillis()
val fileName = "$date.txt"
val contentValues = ContentValues().apply {
put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
put(MediaStore.MediaColumns.RELATIVE_PATH,
"$dirDest${File.separator}")
put(MediaStore.Files.FileColumns.IS_PENDING, 1)
}
}
val imageUri = context.contentResolver.insert(collection, contentValues)
withContext(Dispatchers.IO) {
imageUri?.let { uri ->
context.contentResolver.openOutputStream(uri, "w").use { out -> out?.write(text.toByteArray())
}
contentValues.clear()
contentValues.put(MediaStore.Files.FileColumns.IS_PENDING, 0)
context.contentResolver.update(uri, contentValues, null, null)
}
}
} catch (e: FileNotFoundException) {
null
}
}
}
For Updating the already existing file , do the following . After creating file for the first time I have saved the imageUri in a global variable (If you want to store it permanently / or for a while you can use Jetpack Datastore / Shared Preference to save the same ):
suspend fun updateData(context: Context,text : String){
withContext(Dispatchers.IO) {
try {
val collection =
MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
val dirDest = File(
Environment.DIRECTORY_DOCUMENTS,
context.getString(R.string.app_name)
)
val fileName = "test.txt"
val contentValues = ContentValues().apply {
put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
put(
MediaStore.MediaColumns.RELATIVE_PATH,
"$dirDest${File.separator}"
)
put(MediaStore.Files.FileColumns.IS_PENDING, 1)
}
withContext(Dispatchers.IO) {
imageUri?.let { uri ->
context.contentResolver.openOutputStream(uri, "wa").use { out ->
out?.write(text.toByteArray())
}
contentValues.clear()
contentValues.put(MediaStore.Files.FileColumns.IS_PENDING, 0)
context.contentResolver.update(uri, contentValues, null, null)
}
}
} catch (e: FileNotFoundException) {
null
}
}
}
For Reading the File , Do the following :
suspend fun read(context: Context, source: Uri): String = withContext(Dispatchers.IO) {
val resolver: ContentResolver = context.contentResolver
resolver.openInputStream(source)?.use { stream -> stream.readText() }
?: throw IllegalStateException("could not open $source")
}
private fun InputStream.readText(charset: Charset = Charsets.UTF_8): String =
readBytes().toString(charset)
This is how the final code looks like :
class MainActivity : AppCompatActivity() {
private lateinit var btn: Button
private var imageUri: Uri? = null
private lateinit var btn2: Button
private lateinit var btn3 : Button
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
btn = findViewById(R.id.btnAdd)
btn2 = findViewById(R.id.getText)
btn3 = findViewById(R.id.updateText)
btn.setOnClickListener {
lifecycleScope.launch {
saveDocument(applicationContext, "Original ")
}
}
btn3.setOnClickListener {
lifecycleScope.launch {
updateData(applicationContext,"Appended")
}
}
btn2.setOnClickListener {
lifecycleScope.launch {
imageUri?.let { it1 ->
val data = read(applicationContext, it1)
Toast.makeText(applicationContext, "The data is $data ", Toast.LENGTH_LONG)
.show()
}
}
}
}
suspend fun saveDocument(context: Context, text: String) {
withContext(Dispatchers.IO) {
try {
val collection =
MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
val dirDest = File(
Environment.DIRECTORY_DOCUMENTS,
context.getString(R.string.app_name)
)
val date = System.currentTimeMillis()
val fileName = "test.txt"
val contentValues = ContentValues().apply {
put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
put(
MediaStore.MediaColumns.RELATIVE_PATH,
"$dirDest${File.separator}"
)
put(MediaStore.Files.FileColumns.IS_PENDING, 1)
}
imageUri = context.contentResolver.insert(collection, contentValues)
withContext(Dispatchers.IO) {
imageUri?.let { uri ->
context.contentResolver.openOutputStream(uri, "w").use { out ->
out?.write(text.toByteArray())
}
contentValues.clear()
contentValues.put(MediaStore.Files.FileColumns.IS_PENDING, 0)
context.contentResolver.update(uri, contentValues, null, null)
}
}
} catch (e: FileNotFoundException) {
null
}
}
}
suspend fun updateData(context: Context, text: String) {
withContext(Dispatchers.IO) {
try {
val collection =
MediaStore.Files.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
val dirDest = File(
Environment.DIRECTORY_DOCUMENTS,
context.getString(R.string.app_name)
)
val fileName = "test.txt"
val contentValues = ContentValues().apply {
put(MediaStore.MediaColumns.DISPLAY_NAME, fileName)
put(
MediaStore.MediaColumns.RELATIVE_PATH,
"$dirDest${File.separator}"
)
put(MediaStore.Files.FileColumns.IS_PENDING, 1)
}
withContext(Dispatchers.IO) {
imageUri?.let { uri ->
context.contentResolver.openOutputStream(uri, "wa").use { out ->
out?.write(text.toByteArray())
}
contentValues.clear()
contentValues.put(MediaStore.Files.FileColumns.IS_PENDING, 0)
context.contentResolver.update(uri, contentValues, null, null)
}
}
} catch (e: FileNotFoundException) {
null
}
}
}
suspend fun read(context: Context, source: Uri): String = withContext(Dispatchers.IO) {
val resolver: ContentResolver = context.contentResolver
resolver.openInputStream(source)?.use { stream -> stream.readText() }
?: throw IllegalStateException("could not open $source")
}
private fun InputStream.readText(charset: Charset = Charsets.UTF_8): String =
readBytes().toString(charset)
I have three buttons . With the first I create a file , then the uri gets stored in the global variable . Then onClick of second button I add to the already existing file and then read the file using the third button using the same imageUri stored in the global variable
This is the demo for the same . Check when the buttons are being pressed and the output in the form of Toast at the bottom .