NSMutableArray *array = [[NSMutableArray alloc]initWithArray: [self.navigationController viewControllers]]; // 删除栈中的一个viewcontroller
[array removeObjectAtIndex:]; // 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;