This works for me, the source is here
int MY_PERMISSIONS_REQUEST_CAMERA=0;
// Here, this is the current activity
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)
{
if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA))
{
}
else
{
ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUEST_CAMERA );
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}