推出一个透明的Viewcontroller控制器

A页面推出B页面：

在A页面里写下面的代码

LoginTipViewController * loginTipVC = [LoginTipViewController new];

self.definesPresentationContext = YES;

UIColor *color = [UIColor blackColor];

loginTipVC.view.backgroundColor = [color colorWithAlphaComponent:0.3];

loginTipVC.modalPresentationStyle = UIModalPresentationOverCurrentContext;

[self presentViewController:loginTipVC animated:NO completion:nil];