UIImageView上添加Button不能响应点击事件

UIImageView *backImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0,self.view.frame.size.height-UITABBAR_HEIGHT-216-39, 320, 43) ];

    [backImageView setUserInteractionEnabled:YES];//使添加其上的button有点击事件

    [backImageView setImage:[UIImage imageNamed:@"navigationBar.png"]];

    [backScroll addSubview:backImageView];

    

    UIButton *loginButton = [UIButton alloc];

    [loginButton setFrame:CGRectMake(10, 0, 40, 43)];

    [loginButton setTitle:@"hello" forState:UIControlStateNormal];

    [loginButton addTarget:self action:@selector(loginOrLogout) forControlEvents:UIControlEventTouchUpInside];

    [backImageView addSubview:loginButton];