为什么UIScrollViewDelegate不工作?

@interface HaveScrollController : UIViewController <UIScrollViewDelegate>{
    IBOutlet UIScrollView *scrollView;
    IBOutlet UIView *firstView;
    IBOutlet UIView *secondView;
    IBOutlet UIView *thridView;
    IBOutlet UIView *fourthView;
}


@property (retain, nonatomic) UIScrollView *scrollView;
@property (retain, nonatomic) UIView *firstView;
@property (retain, nonatomic) UIView *secondView;
@property (retain, nonatomic) UIView *thridView;
@property (retain, nonatomic) UIView *fourthView;


@end

.m是这样的:

@synthesize scrollView,firstView,secondView,thridView,fourthView;
- (void)viewDidLoad {
    [super viewDidLoad];
    [self.view addSubview:scrollView];

    scrollView.delegate = self;
}


- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    NSLog(@"scroll detected");
}

@end

@interface TestAppController : UIViewController <UIScrollViewDelegate,UIActionSheetDelegate, UITextFieldDelegate> {
    HaveScrollController *scollViewController;
}

.m在loadView方法中是这样的:

scollViewController = [[HaveScrollController alloc] initWithNibName:@"HaveScrollView" bundle:nil];

[mainCanvas addSubview: buttomScollViewController.view];
self.view = mainCanvas;
[mainCanvas release];

当我试图滚动视图,但“滚动检测”没有显示。我做错了什么?谢谢您。