手动调整导航控制器中的viewcontroller

  NSMutableArray *array = [[NSMutableArray alloc]initWithArray: [self.navigationController viewControllers]];
 
 //  删除栈中的一个viewcontroller
    [array removeObjectAtIndex:2];
  
//  清掉栈中的所有viewcontroller并跳到指定viewcontroller
   [array removeAllObjects];
    pxViewController *px = [[pxViewController alloc]init];
    [array addObject:px];
    [px release];
    
    
    self.navigationController.viewControllers = array;