Interface

Resistance can be enabled or disabled through the following property:

/**
 *  This flag defines whether or not resistance is enabled on the scroll view.
 *  If this is set to NO, both @c resistanceFactor and @c resistanceProgressionRatio
 *  remain unused. Otherwise, if set to YES, resistance is applied based on those two values.
 */
@property (nonatomic, assign) IBInspectable BOOL shouldApplyResistance;

When enabled, resistance is applied using a resistanceFactor and a resistanceProgressionRatio:

/**
 *  This property defines the base value of how resistant the scroll view is when
 *  performing overscroll operations. Please look at @c resistanceProgressionRatio
 *  in order to achieve progressive resistance during an overscroll operation.
 */
@property (nonatomic, assign) IBInspectable CGFloat resistanceFactor;

/**
 *  This property affects how much more resistant the scroll view becomes as the user
 *  continues performing overscroll operations. If this value is 0 the resistance will
 *  be defined solely by @c resistanceFactor and it will remain the same throughout
 *  the overscroll operation; otherwise, it will impact how much resistance is seen
 *  when overscrolling.
 *
 *  Values between 0 and 1 seem to work best with the current implementation.
 */
@property (nonatomic, assign) IBInspectable CGFloat resistanceProgressionRatio;

It is also possible to define an execution block that is run every time the UIScrollView's delegate method scrollViewDidScroll: is called. The block is executed after the resistance is applied so that the contentOffset value is adjusted when running the block:

/**
 *  If defined, this block is run every time the scroll view's delegate method
 *  @c scrollViewDidScroll: is called. Since this class sets itself as the scroll 
 *  view's delegate, this may be used when external code needs to be executed.
 */
@property (nonatomic, copy) void (^scrollViewDidScrollExecutionBlock)(UIScrollView *);

If usages of this class need to implement the UIScrollView's delegate methods for some other tasks, they can do so simply by setting the delegate. EAResistantScrollView will be responsible for redirecting any delegate calls to the appropriate object.

Usage

To run the example project, clone the repo, and run pod install from the Example directory first.

Installation

Import:

#import <EAResistantScrollView/EAResistantScrollView.h>

Author

Edgar Antunes

License

EAResistantScrollView is available under the MIT license. See the LICENSE file for more info.