如何在聊天页面 collectionView 顶部添加自定义视图

[anon72240634]

- (void)viewDidLoad {
    [super viewDidLoad];
    CGRect frame = self.conversationMessageCollectionView.frame;
    frame.origin.y += 100;
    frame.size.height -= 100;
    self.conversationMessageCollectionView.frame = frame;
    UIView *customView = [[UIView alloc] initWithFrame:CGRectMake(0, self.navigationController.navigationBar.frame.size.height + [[UIApplication sharedApplication] statusBarFrame].size.height, [UIScreen mainScreen].bounds.size.width, 100)];
    customView.backgroundColor = [UIColor redColor];
    [self.view addSubview:customView];
}

具体效果图如下：