设置button为圆形

通过layler

// 创建头像视图

    UIButton *logoButton = [[UIButton alloc] init];
    logoButton.frame = CGRectMake(50, 50, 100, 100);
    logoButton.layer.cornerRadius = 50;
    logoButton.backgroundColor = [UIColor redColor];
    [self.view addSubview:logoButton];