//在页面显示时将透明打开

-(void)viewWillAppear:(BOOL)animated{

    [super viewWillAppear:animated];

    [self.navigationController.navigationBar.subviews firstObject].hidden = YES;

}

//关闭时显示 

-(void)viewWillDisappear:(BOOL)animated{

    

    [super viewWillDisappear:animated];

    [self.navigationController.navigationBar.subviews firstObject].hidden = NO;

}