IOS注意：windows上加view，view下移20

AppDelegate * appDelegate = [[UIApplication sharedApplication] delegate];
AppRaterView * raterView = [[AppRaterView alloc] initWithNibName:@"AppRaterView" bundle:nil];
    CGRect f = CGRectOffset(raterView.view.frame, 0.0, 20.0);
    raterView.view.frame = f;
    [appDelegate.window addSubview:raterView.view];