Xcode 双击可使用UIScrollView进行缩放

我正在使用苹果的源代码。我敢肯定，这只是我弄糟的一个片段。我有一个通过编程制作的表单。当我双击识别器时，它会启动并进行动作，但实际上它不会缩放。有什么建议吗？谢谢你的帮助

imageScrollView.delegate=self;

CGRect fullScreenRect=[[UIScreen mainScreen] applicationFrame];
imageScrollView=[[UIScrollView alloc]initWithFrame:fullScreenRect];
imageScrollView.contentSize=CGSizeMake(750,1250);
imageScrollView.minimumZoomScale=1.0;
imageScrollView.maximumZoomScale=5.0;
[imageScrollView setZoomScale:imageScrollView.minimumZoomScale];
self.view=imageScrollView;
[imageScrollView release];

向scrollview添加了一组UItextfields/标签。 aircraftType=[[UITextField alloc]initWithFrame:CGRectMake（170,32,150,15）]； aircraftType.font=[UIFont systemFontOfSize:10]； aircraftType.borderStyle=UITextBorderStyleRoundedRect； aircraftType.placeholder=@“Aicraft Type”； aircraftType.delegate=自身； [self.view addSubview:aircraftType]

#pragma mark UIScrollViewDelegate methods
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return [imageScrollView viewWithTag:ZOOM_VIEW_TAG];
}

#pragma mark TapDetectingImageViewDelegate methods
- (void)handleDoubleTap:(UIGestureRecognizer *)gestureRecognizer {
    // double tap zooms in

    float newScale = [imageScrollView zoomScale] * ZOOM_STEP;
    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
    [imageScrollView zoomToRect:zoomRect animated:YES];

}


#pragma mark Utility methods
- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center {

    CGRect zoomRect;

    // the zoom rect is in the content view's coordinates.
    //    At a zoom scale of 1.0, it would be the size of the imageScrollView's bounds.
    //    As the zoom scale decreases, so more content is visible, the size of the rect grows.
    zoomRect.size.height = [imageScrollView frame].size.height / scale;
    zoomRect.size.width  = [imageScrollView frame].size.width  / scale;

    // choose an origin so as to get the right center.
    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);
    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);



    return zoomRect;
}