- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  UIImageView *imageview=[[UIImageView alloc]init];
  imageview.frame=CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
  imageview.image=[UIImage imageNamed:@"girl.png"];
  [self.view addSubview:imageview];
  UIButton *Btn=[[UIButton alloc]init];
  Btn.frame=CGRectMake(20, 100, 50, 50);
  Btn.backgroundColor=[UIColor blueColor];
  [Btn addTarget:self action:@selector(btnclick) forControlEvents:UIControlEventTouchUpInside];
  [imageview addSubview:Btn];
  imageview.userInteractionEnabled=YES;
}
-(void)btnclick
{
  BackViewController *backVc=[[BackViewController alloc]init];
  [self presentViewController:backVc animated:YES completion:nil];
}

- (instancetype)init
{
  self = [super init];
  if (self) {
    self.view.backgroundColor=[UIColor colorWithWhite:0 alpha:0.4];
    self.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    self.modalPresentationStyle = UIModalPresentationOverFullScreen;
  }
  return self;
}

//只设置黑白背景色 white后面的参数表示灰度，从0-1之间表示从黑到白的变化，alpha就是你想调整的透明度。
  blackV.backgroundColor = [UIColor colorWithWhite:0.f alpha:0.7]; 
//设置任意颜色的背景色
blackV.backgroundColor = [UIColor colorWithRed:122/255.0 green:123/255.0 blue:234/255.0 alpha:0.7]; 
UIColor *color = [UIColor blackColor];
bgView.backgroundColor = [color colorWithAlphaComponent:0.5];

- (void)viewDidLoad {
  [super viewDidLoad];
  UIButton *btn=[UIButton buttonWithType:UIButtonTypeCustom];
  btn.frame=CGRectMake(50, 300, 50, 50);
//  btn.backgroundColor=[UIColor blueColor];
  [self.view addSubview:btn];
  [btn setBackgroundImage:[UIImage imageNamed:@"userGuideBtnBG_unClear.png"] forState:UIControlStateNormal];
  [btn addTarget:self action:@selector(btnclick) forControlEvents:UIControlEventTouchUpInside];
  btn.backgroundColor=[UIColor clearColor];
  btn.alpha=0.75;
  UIView *view1=[[UIView alloc]init];
  view1.backgroundColor=[UIColor blackColor];
  view1.alpha=0.75;
  [self.view addSubview:view1];
  view1.frame=CGRectMake(0, 0, self.view.frame.size.width, 300);
  UIView *view2=[[UIView alloc]init];
  view2.backgroundColor=[UIColor blackColor];
  view2.alpha=0.75;
  [self.view addSubview:view2];
  view2.frame=CGRectMake(0, 300+50, self.view.frame.size.width, self.view.frame.size.height-50-300);
  UIView *view3=[[UIView alloc]init];
  view3.backgroundColor=[UIColor blackColor];
  view3.alpha=0.75;
  [self.view addSubview:view3];
  view3.frame=CGRectMake(0, 300, 50, 50);
  UIView *view4=[[UIView alloc]init];
  view4.backgroundColor=[UIColor blackColor];
  view4.alpha=0.75;
  [self.view addSubview:view4];
  view4.frame=CGRectMake(50+50, 300, self.view.frame.size.width-50-50, 50);
  UILabel *titlelabel=[[UILabel alloc]init];
  titlelabel.frame=CGRectMake(100, 350,100,50 );
  [self.view addSubview:titlelabel];
  titlelabel.text=@"这是新功能";
  titlelabel.textColor=[UIColor whiteColor];
}
-(void)btnclick
{
  [self dismissViewControllerAnimated:YES completion:nil];
}