Permission from manifest doesn’t work in Android 6

Thanks to CommonsWare’s blog post, I got some clue.

Assuming your code is in Activity or Fragment, check the overlay permission and make a request for it if necessary:

public static int OVERLAY_PERMISSION_REQ_CODE = 1234;

public void someMethod() {
    if (!Settings.canDrawOverlays(this)) {
        Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                Uri.parse("package:" + getPackageName()));
        startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE);
    }
}

Then, re-check the permission for better UX:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
        if (!Settings.canDrawOverlays(this)) {
            // SYSTEM_ALERT_WINDOW permission not granted...
        }
    }
}