secure window with color

secure_window_color.m

- (void)applicationWillResignActive:(UIApplication *)application {
  UIView *__autoreleasing colorView =
      [[UIView alloc] initWithFrame:self.window.frame];
  // Can be any integer you’re not using as a tag.
  colorView.tag = 9999;
  
  // Here we used white as the subview color.
  colorView.backgroundColor = [UIColor whiteColor];
  [self.window addSubview:colorView];
  [self.window bringSubviewToFront:colorView];
}

— (void)applicationDidBecomeActive:(UIApplication *)application {
  UIView *colorView = [self.window viewWithTag:9999];
  [colorView removeFromSuperview];
}