Android 6(M) permission issue (create directory not working)

Question

I have this code for creating directory for saving pictures:

        File storageDir = null;
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {                
            storageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "myphoto");
            if (!storageDir.mkdirs()) {                    
                if (!storageDir.exists()){                       
                    Log.d("photo", "failed to create directory");
                    return null;
                }
            }
        }
        return storageDir;

storeDir returns "/storage/emulated/0/Pictures/myphoto/" below android 6 and on android 6 it returns null.

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

buildToolVersion 23 targetSdkVersion 23

How to fix?

Answer 1

As @CommonsWare answered, there is run-time permission asking concept on Android M, so in new approach, permissions are not asked when installing the app but when trying to use specific feature of phone which requests permission, at run-time. User later can disable permission from phone settings->app->yourapp->permissions as well. So you have to check before doing something with that permission, and ask user:

int REQUEST_WRITE_EXTERNAL_STORAGE=1;
////...
        File storageDir = null;
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
            //RUNTIME PERMISSION Android M
            if(PackageManager.PERMISSION_GRANTED==ActivityCompat.checkSelfPermission(context,Manifest.permission.WRITE_EXTERNAL_STORAGE)){
                storageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "myPhoto");
            }else{
                requestPermission(context);
            }    

        } 
        return storageDir;
////...
        private static void requestPermission(final Context context){
        if(ActivityCompat.shouldShowRequestPermissionRationale((Activity)context,Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
            // Provide an additional rationale to the user if the permission was not granted
            // and the user would benefit from additional context for the use of the permission.
            // For example if the user has previously denied the permission.

            new AlertDialog.Builder(context)
                    .setMessage(context.getResources().getString(R.string.permission_storage))
                    .setPositiveButton(R.string.tamam, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCompat.requestPermissions((Activity) context,
                            new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                            REQUEST_WRITE_EXTERNAL_STORAGE);
                }
            }).show();

        }else {
            // permission has not been granted yet. Request it directly.
            ActivityCompat.requestPermissions((Activity)context,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                    REQUEST_WRITE_EXTERNAL_STORAGE);
        }
    }

///...

    @Override
    public void onRequestPermissionsResult(int requestCode,String permissions[], int[] grantResults) {
        switch (requestCode) {
            case UtilityPhotoController.REQUEST_WRITE_EXTERNAL_STORAGE: {
                if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(context,
                            getResources().getString(R.string.permission_storage_success),
                            Toast.LENGTH_SHORT).show();

                } else {
                    Toast.makeText(context,
                            getResources().getString(R.string.permission_storage_failure),
                            Toast.LENGTH_SHORT).show();
                    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
                }
                return;
            }
        }
    }