Problem when scrolling ScrollView control?

I have a problem with my UIScrollView. It's visible but I can't scroll it.

CGRect frame = CGRectMake(20, 90,280,1000);
scroll1=[[UIScrollView alloc]initWithFrame:frame];
scroll1.contentSize = CGSizeMake(280,1000);
scroll1.backgroundColor=[UIColor grayColor];

//scroll1.delegate=scroll1;
[scroll1 setUserInteractionEnabled:TRUE];
[scroll1 setPagingEnabled:TRUE];
[scrol开发者_如何学Gol1 setScrollEnabled:TRUE];
[scroll1 showsVerticalScrollIndicator];

Thanks in advance.

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You've set the frame to the same width and height as the content.
Try a smaller frame like (20, 90, 200, 300).