ViewControlloer常用背景图设置

@property(nonatomic,strong)UIImageView*bgImageView;

//背景图
 _bgImageView = [[UIImageView alloc]initWithFrame:self.view.frame]; 
 _bgImageView.userInteractionEnabled = YES; 
 _bgImageView.backgroundColor = [UIColor whiteColor];
 [self.view addSubview:_bgImageView];