I want to request permission at app runtime android Marshmallow ..!

Question

i am making an android app on my music player in which i have populated all the songs in my device using a listview,but in android 6.0 my app crashes as i open it.It doesn't crash anymore when i give it storage permissions manually in app info,and then my songs are displayed. I have used the android 6.0 request permissions,and it results in asking the user for asking access to storage,but then it doesn't shows the list anymore.I am stuck on this...!

MainActivity.java

public class MainActivity extends AppCompatActivity implements MediaPlayerControl  {
    private ArrayList<Song> songList;
    private ListView songView;
    private MusicController controller;
    private MusicService musicSrv;
    private Intent playIntent;
    private boolean musicBound=false;
    private boolean paused=false, playbackPaused=false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        songView = (ListView) findViewById(R.id.song_list);
        songList = new ArrayList<Song>();

    //Android 6.0
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED) {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.READ_EXTERNAL_STORAGE)) {


        } else {

        }
    } else {
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},1002);
    }
}
//Android 6.0
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    switch (requestCode){
        case 1002:
            if(grantResults.length>0 && grantResults[0]==PackageManager.PERMISSION_GRANTED){
                getSongList();
                // List songs in Alphabetical Order
                Collections.sort(songList, new Comparator<Song>() {
                    public int compare(Song a, Song b) {
                        return a.getTitle().compareTo(b.getTitle());
                    }
                });

                SongAdapter songAdt = new SongAdapter(this, songList);
                songView.setAdapter(songAdt);
                setController();
            }else{

            }
            return;
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.action_shuffle:
            musicSrv.setShuffle();
            break;
        case R.id.action_end:
            stopService(playIntent);
            musicSrv = null;
            System.exit(0);
            break;
    }
    return super.onOptionsItemSelected(item);
}
@Override
protected void onStart() {
    super.onStart();
    if(playIntent==null) {
        playIntent = new Intent(this, MusicService.class);
        bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
        startService(playIntent);
    }
}

@Override
protected void onPause() {
    super.onPause();
    paused=true;
}

@Override
protected void onResume() {
    super.onResume();
    if(paused){
        setController();
        paused=false;
    }
}
@Override
protected void onStop() {
    controller.hide();
    super.onStop();
}
@Override
protected void onDestroy() {
    stopService(playIntent);
    musicSrv=null;
    super.onDestroy();
}
public void songPicked(View view){
    musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
    musicSrv.playSong();
    if(playbackPaused){
        setController();
        playbackPaused=false;
    }controller.show(0);
}

//connect to the service
private ServiceConnection musicConnection = new ServiceConnection(){

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        MusicService.MusicBinder binder = (MusicService.MusicBinder)service;
        //get service
        musicSrv = binder.getService();
        //pass list
        musicSrv.setList(songList);
        musicBound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        musicBound = false;
    }
};

public void getSongList() {
    //retrieve song info
    ContentResolver musicResolver = getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);

    if(musicCursor!=null && musicCursor.moveToFirst()){
        //get columns
        int titleColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.TITLE);
        int idColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex
                (android.provider.MediaStore.Audio.Media.ARTIST);
        //add songs to list
        do {
            long thisId = musicCursor.getLong(idColumn);
            String thisTitle = musicCursor.getString(titleColumn);
            String thisArtist = musicCursor.getString(artistColumn);
            songList.add(new Song(thisId, thisTitle, thisArtist));
        }
        while (musicCursor.moveToNext());
    }
}

Answer 1

You can use this android library for to make handling runtime permissions a whole lot easier.

If your Activity subclasses PermisoActivity, requesting a permission is as simple as:

    Permiso.getInstance().requestPermissions(new Permiso.IOnPermissionResult() {
    @Override
    public void onPermissionResult(Permiso.ResultSet resultSet) {
        if (resultSet.areAllPermissionsGranted()) {
            // Permission granted!
        } else {
            // Permission denied.
        }
    }

    @Override
    public void onRationaleRequested(Permiso.IOnRationaleProvided callback, String... permissions) {
        Permiso.getInstance().showRationaleInDialog("Title", "Message", null, callback);
    }
}, Manifest.permission.READ_EXTERNAL_STORAGE);

Gradle

 dependencies {
    compile 'com.greysonparrelli.permiso:permiso:0.2.0'
}

You can add multiple permissions also please visit link shared. You can get All information in details.

Answer 2

This code will allow you to request permission at run time by checking if the permission has been granted and if not, ask the user to enable the permission.

if(ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, MY_PERMISSION_RESPONSE);
        }

The permission being checked for in this case is to do with location services. Just replace ACCESS_COARSE_LOCATION with whatever permission you wish to ask for.