蒙板_upView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5];

 //加到window上，由于再加上的view也透明了 所以用以下方法解决

self.upView.frame = CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HIGHT);_upView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5];[WINDOW addSubview:self.upView];UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapAction:)];[self.upView addGestureRecognizer:tap];