How To Use UIScrollView in Your iPhone App
Implementing UIScrollView in Cocoa-Touch
This example starts with a View Based Application with the image already in the Resources group. You can create this yourself using XCode’s “New Project” menu item.
Add IBOutlets
Select the view controller interface file and add the scroll view IBOutlet and the image view property:
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#import <UIKit/UIKit.h> @interface UseScrollViewViewController : UIViewController { IBOutlet UIScrollView *scrollView; UIImageView *imageView; } @property (nonatomic, retain) UIScrollView *scrollView; @property (nonatomic, retain) UIImageView *imageView; @end |
Finish implementing the IBOutlet and property in the implementation file.
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#import "UseScrollViewViewController.h" @implementation UseScrollViewViewController @synthesize scrollView, imageView; - (void)dealloc { [super dealloc]; [imageView release]; [scrollView release]; } @end |
Adopt the Delegate Protocol
To use UIScrollView we must adopt the UIScrollViewDelegate protocol. Once we do our view controller may act on behalf of our scroll view. Simple add this after the UIViewController sublcass: <UIScrollViewDelegate>.
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#import <UIKit/UIKit.h> @interface UseScrollViewViewController : UIViewController <UIScrollViewDelegate> { IBOutlet UIScrollView *scrollView; UIImageView *imageView; } @property (nonatomic, retain) UIScrollView *scrollView; @property (nonatomic, retain) UIImageView *imageView; @end |
Implement the Delegate Method viewForZoomingInScrollView
Implementing this method will allow the scroll view to provide the pinching and zooming behavior demonstrated in the video.
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#import "UseScrollViewViewController.h" @implementation UseScrollViewViewController ... - (UIView *)viewForZoomingInScrollView:(UIScrollView *) scrollView{ return imageView; } ... @end |
Create the Image View
The image view will be used to display the image on the view. This is pretty straightforward: you will simple create the object and set it to the property we defined earlier in the viewDidLoad method.
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- (void)viewDidLoad { [super viewDidLoad]; UIImageView *tempImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Beer-Sign-On-Wall.jpg"]]; self.imageView = tempImageView; [tempImageView release]; } |
Set the UIScrollView Properties
Since we are using Interface Builder to add the scroll view we do not need to create it here. But, we will be setting some of the scroll view properties. Note that we add the image view to the scroll view’s subview collection.
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- (void)viewDidLoad { ... scrollView.contentSize = CGSizeMake (imageView.frame.size.width, imageView.frame.size.height); scrollView.maximumZoomScale = 4.0; scrollView.minimumZoomScale = 0.75; scrollView.clipsToBounds = YES; scrollView.delegate = self; [scrollView addSubview:imageView]; } |
Add Scroll View in Interface Builder
Now all you need to do is add your scroll view in interface builder and hook it up to the IBOutlet you defined in the view controller!
A good article on UIScrollView
