Uiscrollbar不滚动

Question

我为横向视图实现了滚动条：

//Add scrollview
    scrollview=[[UIScrollView alloc]initWithFrame:CGRectMake(0,0,1024,768)];
    scrollview.delegate = self;
    scrollview.showsVerticalScrollIndicator=YES;
    scrollview.scrollEnabled=YES;
    scrollview.userInteractionEnabled=YES;
    scrollview.contentOffset = CGPointMake(0, 0);
    scrollview.contentSize = CGSizeMake(1024,2000);
    [self.view addSubview:scrollview];

//将子视图添加到scrollview

[self generateSubtaskElements:allObjects];

我尝试更改contentSize，但没有任何事情发生。我无法掩盖这一观点。