Android app can't read external storage files

Question

I'm creating an app for a private use only... it's not so important then, respect your time :P

What I want to make is an app that reads from a database and plays sounds. I've already made the database and I am able to play sound from res/raw folder. However, there are thousands of files to play and some new ones will be a part of the app and other will be deleted in the future. So, adding a simple file makes me to download the whole app (~1 GB) each time (or maybe I'm wrong?). Instead, I thought of reading an Excel file and playing sounds from SD card then. But I can't... as far as i know:

Apps are not allowed to write (delete, modify ...) to external storage except to their package-specific directories.

I put the files into the /storage/emulated/0/Android/data/my_package_folder/files folder. I've read really many topics and nothing helped me.

Environment.MEDIA_MOUNTED.equals(extStorageState) //returns true
Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState) //returns false

I tried a few ways of creating new file object or playing the sound with the mediaplayer (as I've said before, there's no problem with playing res/raw files) but file.exists always returns false or sound doesn't play:

String filePath = getExternalFilesDir(null) + "/myfile.mp3"; //returns correct file path
File file = new File(filePath);

OR

File file = new File(getExternalFilesDir(null).getPath(), "myfile.mp3");

OR

MediaPlayer mp;
mp = MediaPlayer.create(this, Uri.parse(getExternalFilesDir(null).getPath() + "/myfile.mp3"));

The minSdkVersion is set to 19 so I don't need that line in Manifest:

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

I have included that line and nothing changed:

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

I was also trying to do that with other file extensions. Also, the solution from here didn't help. My phone is Samsung Galaxy Grand Prime (SM-G530FZ), Android v. 5.0.2. Help, please! :)

Answer 1

Here is the code @Nisarg, had to clean it a bit:

import android.Manifest;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity implements OnClickListener {

Button readExcelButton;
static String TAG = "ExelLog";
MediaPlayer mpintro;

@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (Build.VERSION.SDK_INT == Build.VERSION_CODES.M) {
        Toast.makeText(this, "Permission checking", Toast.LENGTH_SHORT).show();
        checkPermission();
    }

    readExcelButton = (Button) findViewById(R.id.readExcel);
    readExcelButton.setOnClickListener(this);

}

public void onClick(View v)
{
    switch (v.getId())
    {
        case R.id.readExcel:
            String filePath = getExternalFilesDir(null) + "/p0000.mp3";
            File file = new File(filePath);
            file.setReadable(true);
            file.setWritable(true);

            if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {
                Toast.makeText(this, "Ext storage not available or read only", Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(this, "Ext storage available", Toast.LENGTH_SHORT).show();
            }

            if (file.exists()){
                Toast.makeText(this, "File found", Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(this, getExternalFilesDir(null) + "/p0000.mp3 - File not found", Toast.LENGTH_LONG).show();
            }

            break;
    }
}

private void checkPermission() {
    if (ContextCompat.checkSelfPermission(this,
            Manifest.permission.WRITE_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this,
            Manifest.permission.READ_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED) {//Can add more as per requirement

        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},
                123);

    } else {

    }
}

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    switch (requestCode) {
        case 123: {

            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED)     {
                //Peform your task here if any
            } else {

                checkPermission();
            }
            return;
        }
    }
}

public static boolean isExternalStorageReadOnly() {
    String extStorageState = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
        return true;
    }
    return false;
}

public static boolean isExternalStorageAvailable() {
    String extStorageState = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
        return true;
    }
    return false;
}

}

Answer 2

if your targetSdk is 23 than you have to check permissions like this for marshmallow and above devices

if (Build.VERSION.SDK_INT == Build.VERSION_CODES.M) {
    checkPermission();
}
else {
}


private void checkPermission() {
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this,
            Manifest.permission.READ_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED) {//Can add more as per requirement

            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},
                    123);

        } else {

        }
}

@Override
public void onRequestPermissionsResult(int requestCode,
                                   String permissions[], int[] grantResults)   
   {
    switch (requestCode) {
        case 123: {


 if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED)     {
   //Peform your task here if any
    } else {

        checkPermission();
    }
        return;
    }
}
}

Answer 3

You also have to have the permission READ_EXTERNAL_STORAGE; Either write or read is not enough when it comes to external storage, as you have to use both

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

You can also read more about external data writing in the declaration

The reason you cannot read is because you didn't add that permission. A good rule is if you only need to read, only use read permission. But if you need to write you need the write and the read permission

EDIT:

When loading the directory, try this:

file.setReadable(true);
file.setWritable(true);

Note: the value 'file' here is for the directory, not each separate file(all though that works fine too)

From the declaration:

This permission is enforced starting in API level 19. Before API level 19, this permission is not enforced and all apps still have access to read from external storage.

If I am correct that means the permission has to be there from API 19 and up, but not before API 19