UIScrollView

UIScrollView

一.UIScrollView介绍

The UIScrollView class provides support for displaying content that is larger than the size of the application’s window. It enables users to scroll within that content by making swiping gestures, and to zoom in and back from portions of the content by making pinching gestures.

UIScrollView类提供了支持显示的内容比应用程序的窗口的大小。它使用户能够滚动内容通过划动手势,和放大,从部分内容通过缩放手势。

UIScrollView is the superclass of several UIKit classes including UITableView and UITextView.UIScrollView是几个UIKit类的超类包括UITableView和UITextView。

The central notion of a UIScrollView object (or, simply, a scroll view) is that it is a view whose origin is adjustable over the content view. It clips the content to its frame, which generally (but not necessarily) coincides with that of the application’s main window. A scroll view tracks the movements of fingers and adjusts the origin accordingly. The view that is showing its content “through” the scroll view draws that portion of itself based on the new origin, which is pinned to an offset in the content view. The scroll view itself does no drawing except for displaying vertical and horizontal scroll indicators. The scroll view must know the size of the content view so it knows when to stop scrolling; by default, it “bounces” back when scrolling exceeds the bounds of the content.

UIScrollView对象的核心概念(或者简单,滚动视图),它是一个视图,其起源可调内容视图。它剪辑的内容框架,通常(但不一定)一致的应用程序的主窗口。一个滚动视图跟踪手指的运动,并相应地调整原点。视图显示其内容”通过“滚动视图本身吸引这部分基于新的来源,这是固定在一个偏移量在内容视图中。滚动视图本身并没有画除了显示垂直和水平滚动指标。滚动视图必须知道内容视图的大小所以它知道何时停止滚动;默认情况下,它“反弹”当滚动超过的范围内容。

The object that manages the drawing of content displayed in a scroll view should tile the content’s subviews so that no view exceeds the size of the screen. As users scroll in the scroll view, this object should add and remove subviews as necessary.

管理的对象的内容显示在滚动视图应该瓷砖内容的子视图,所以没有查看超过屏幕的大小。当用户滚动滚动视图,这个对象应该根据需要添加和删除子视图。

Because a scroll view has no scroll bars, it must know whether a touch signals an intent to scroll versus an intent to track a subview in the content. To make this determination, it temporarily intercepts a touch-down event by starting a timer and, before the timer fires, seeing if the touching finger makes any movement. If the timer fires without a significant change in position, the scroll view sends tracking events to the touched subview of the content view. If the user then drags their finger far enough before the timer elapses, the scroll view cancels any tracking in the subview and performs the scrolling itself. Subclasses can override the touchesShouldBegin:withEvent:inContentView:, pagingEnabled, and touchesShouldCancelInContentView: methods (which are called by the scroll view) to affect how the scroll view handles scrolling gestures.

因为没有滚动条的滚动视图,它必须知道一个触摸信号一个滚动的意图和目的跟踪子视图的内容。使这一决心,暂时拦截代表事件启动一个计时器,计时器大火之前,看到如果触摸手指使任何运动。如果计时器火灾没有显著改变位置,滚动视图发送跟踪事件触动了内容视图的子视图。如果用户然后拖动手指足够远的计时器结束之前,滚动视图取消子视图中的任何跟踪和执行滚动本身。子类可以重写touchesShouldBegin:withEvent:inContentView:pagingEnabled touchesShouldCancelInContentView:方法(由滚动视图调用)影响滚动视图如何处理滚动姿态。

The UIScrollView class can have a delegate that must adopt the UIScrollViewDelegate protocol. For zooming and panning to work, the delegate must implement both viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale:; in addition, the maximum (maximumZoomScale) and minimum ( minimumZoomScale) zoom scale must be different.

UIScrollView类可以有一个委托,必须采用UIScrollViewDelegate协议。缩放和移动工作,委托必须实现两viewForZoomingInScrollView:scrollViewDidEndZooming:withView:atScale:;此外,最大(maximumZoomScale)和最小(minimumZoomScale)缩放尺度必须是不同的。

For information about basic view behaviors, see View Programming Guide for iOS.

信息基本视图的行为,看到视图iOS编程指南。

二.Managing the Display of Content 管理内容的显示

- setContentOffset:animated:

Sets the offset from the content view’s origin that corresponds to the receiver’s origin.

设置偏移量从内容视图的起源相对应的接收器的起源。

Declaration

SWIFT

 func setContentOffset(_ contentOffset: CGPoint, 2 animated animated: Bool) 

OBJECTIVE-C

- (void)setContentOffset:(CGPoint)contentOffset
                animated:(BOOL)animated

 

Parameters

contentOffset	A point (expressed in points) that is offset from the content view’s origin.
animated	YES to animate the transition at a constant velocity to the new offset, NO to make the transition immediate.

contentOffset	一个点(点)表达抵消从内容视图的起源。
animated	是的动画以恒定速度过渡到新的抵消,没有立即转变。

• Availability

  Available in iOS 2.0 and later.

  See Also

  contentOffset

• contentOffset Property

  The point at which the origin of the content view is offset from the origin of the scroll view.

  Declaration

  SWIFT

  var contentOffset: CGPoint

  OBJECTIVE-C

  @property(nonatomic) CGPoint contentOffset

  Discussion

  The default value is CGPointZero. 

  Availability

  Available in iOS 2.0 and later.

  See Also

  – setContentOffset:animated:

• contentSize Property

  The size of the content view.

  Declaration

  SWIFT

  var contentSize: CGSize

  OBJECTIVE-C

  @property(nonatomic) CGSize contentSize

  Discussion

  The unit of size is points. The default size is CGSizeZero. 

  Availability

  Available in iOS 2.0 and later.

• contentInset Property

  The distance that the content view is inset from the enclosing scroll view.

  Declaration

  SWIFT

  var contentInset: UIEdgeInsets

  OBJECTIVE-C

  @property(nonatomic) UIEdgeInsets contentInset

  Discussion

  Use this property to add to the scrolling area around the content. The unit of size is points. The default value is UIEdgeInsetsZero. 

  Availability

  Available in iOS 2.0 and later.

•  

   

   

   

Managing Scrolling

• scrollEnabled Property

  A Boolean value that determines whether scrolling is enabled.

  Declaration

  SWIFT

  var scrollEnabled: Bool

  OBJECTIVE-C

  @property(nonatomic, getter=isScrollEnabled) BOOL scrollEnabled

  Discussion

  If the value of this property is YES , scrolling is enabled, and if it is NO , scrolling is disabled. The default is YES.

  When scrolling is disabled, the scroll view does not accept touch events; it forwards them up the responder chain.

  Availability

  Available in iOS 2.0 and later.

• directionalLockEnabled Property

  A Boolean value that determines whether scrolling is disabled in a particular direction.

  Declaration

  SWIFT

  var directionalLockEnabled: Bool

  OBJECTIVE-C

  @property(nonatomic, getter=isDirectionalLockEnabled) BOOL directionalLockEnabled

  Discussion

  If this property is NO, scrolling is permitted in both horizontal and vertical directions. If this property is YES and the user begins dragging in one general direction (horizontally or vertically), the scroll view disables scrolling in the other direction. If the drag direction is diagonal, then scrolling will not be locked and the user can drag in any direction until the drag completes. The default value is NO

  Availability

  Available in iOS 2.0 and later.

• scrollsToTop Property

  A Boolean value that controls whether the scroll-to-top gesture is enabled.

  Declaration

  SWIFT

  var scrollsToTop: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL scrollsToTop

  Discussion

  The scroll-to-top gesture is a tap on the status bar. When a user makes this gesture, the system asks the scroll view closest to the status bar to scroll to the top. If that scroll view has scrollsToTop set to NO, its delegate returns NO from scrollViewShouldScrollToTop:, or the content is already at the top, nothing happens.

  After the scroll view scrolls to the top of the content view, it sends the delegate a scrollViewDidScrollToTop: message.

  The default value of scrollsToTop is YES. 

  Special Considerations

  On iPhone, the scroll-to-top gesture has no effect if there is more than one scroll view on-screen that has scrollsToTop set to YES.

  Availability

  Available in iOS 2.0 and later.

• - scrollRectToVisible:animated:

  Scrolls a specific area of the content so that it is visible in the receiver.

  Declaration

  SWIFT

  func scrollRectToVisible(_ rect: CGRect,
                animated animated: Bool)

  OBJECTIVE-C

  - (void)scrollRectToVisible:(CGRect)rect
                   animated:(BOOL)animated


  Parameters

  rect	A rectangle defining an area of the content view. The rectangle should be in the coordinate space of the scroll view.
  animated	YES if the scrolling should be animated, NO if it should be immediate.

  Discussion

  This method scrolls the content view so that the area defined by rect is just visible inside the scroll view. If the area is already visible, the method does nothing.

  Availability

  Available in iOS 2.0 and later.

• pagingEnabled Property

  A Boolean value that determines whether paging is enabled for the scroll view.

  Declaration

  SWIFT

  var pagingEnabled: Bool

  OBJECTIVE-C

  @property(nonatomic, getter=isPagingEnabled) BOOL pagingEnabled

  Discussion

  If the value of this property is YES, the scroll view stops on multiples of the scroll view’s bounds when the user scrolls. The default value is NO.

  Availability

  Available in iOS 2.0 and later.

• bounces Property

  A Boolean value that controls whether the scroll view bounces past the edge of content and back again.

  Declaration

  SWIFT

  var bounces: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL bounces

  Discussion

  If the value of this property is YES, the scroll view bounces when it encounters a boundary of the content. Bouncing visually indicates that scrolling has reached an edge of the content. If the value is NO, scrolling stops immediately at the content boundary without bouncing. The default value is YES.

  Availability

  Available in iOS 2.0 and later.

  See Also

  alwaysBounceVertical
alwaysBounceHorizontal

• alwaysBounceVertical Property

  A Boolean value that determines whether bouncing always occurs when vertical scrolling reaches the end of the content.

  Declaration

  SWIFT

  var alwaysBounceVertical: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL alwaysBounceVertical

  Discussion

  If this property is set to YES and bounces is YES, vertical dragging is allowed even if the content is smaller than the bounds of the scroll view. The default value is NO.

  Availability

  Available in iOS 2.0 and later.

  See Also

  alwaysBounceHorizontal

• alwaysBounceHorizontal Property

  A Boolean value that determines whether bouncing always occurs when horizontal scrolling reaches the end of the content view.

  Declaration

  SWIFT

  var alwaysBounceHorizontal: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL alwaysBounceHorizontal

  Discussion

  If this property is set to YES and bounces is YES, horizontal dragging is allowed even if the content is smaller than the bounds of the scroll view. The default value is NO.

  Availability

  Available in iOS 2.0 and later.

  See Also

  alwaysBounceVertical

• - touchesShouldBegin:withEvent:inContentView:

  Overridden by subclasses to customize the default behavior when a finger touches down in displayed content.

  Declaration

  SWIFT

  func touchesShouldBegin(_ touches: Set<UITouch>,
              withEvent event: UIEvent?,
          inContentView view: UIView) -> Bool

  OBJECTIVE-C

  - (BOOL)touchesShouldBegin:(NSSet<UITouch *> *)touches
                 withEvent:(UIEvent *)event
             inContentView:(UIView *)view


  Parameters

  touches	A set of UITouch instances that represent the touches for the starting phase of the event represented by event.
  event	An object representing the event to which the touch objects in touches belong.
  view	The subview in the content where the touch-down gesture occurred.

  Return Value

  Return NO if you don’t want the scroll view to send event messages to view. If you want view to receive those messages, return YES (the default).

  Discussion

  The default behavior of UIScrollView is to invoke the UIResponder event-handling methods of the target subview that the touches occur in. 

  Availability

  Available in iOS 2.0 and later.

  See Also

  – touchesShouldCancelInContentView:

• - touchesShouldCancelInContentView:

  Returns whether to cancel touches related to the content subview and start dragging.

  Declaration

  SWIFT

  func touchesShouldCancelInContentView(_ view: UIView) -> Bool

  OBJECTIVE-C

  - (BOOL)touchesShouldCancelInContentView:(UIView *)view


  Parameters

  view	The view object in the content that is being touched.

  Return Value

  YES to cancel further touch messages to view, NO to have view continue to receive those messages. The default returned value is YES if view is not a UIControl object; otherwise, it returns NO.

  Discussion

  The scroll view calls this method just after it starts sending tracking messages to the content view. If it receives NO from this method, it stops dragging and forwards the touch events to the content subview. The scroll view does not call this method if the value of the canCancelContentTouches property is NO. 

  Availability

  Available in iOS 2.0 and later.

  See Also

  – touchesShouldBegin:withEvent:inContentView:

• canCancelContentTouches Property

  A Boolean value that controls whether touches in the content view always lead to tracking.

  Declaration

  SWIFT

  var canCancelContentTouches: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL canCancelContentTouches

  Discussion

  If the value of this property is YES and a view in the content has begun tracking a finger touching it, and if the user drags the finger enough to initiate a scroll, the view receives a touchesCancelled:withEvent: message and the scroll view handles the touch as a scroll. If the value of this property is NO, the scroll view does not scroll regardless of finger movement once the content view starts tracking. 

  Availability

  Available in iOS 2.0 and later.

• delaysContentTouches Property

  A Boolean value that determines whether the scroll view delays the handling of touch-down gestures.

  Declaration

  SWIFT

  var delaysContentTouches: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL delaysContentTouches

  Discussion

  If the value of this property is YES, the scroll view delays handling the touch-down gesture until it can determine if scrolling is the intent. If the value is NO , the scroll view immediately calls touchesShouldBegin:withEvent:inContentView:. The default value is YES.

  See the class description for a fuller discussion.

  Availability

  Available in iOS 2.0 and later.

• decelerationRate Property

  A floating-point value that determines the rate of deceleration after the user lifts their finger.

  Declaration

  SWIFT

  var decelerationRate: CGFloat

  OBJECTIVE-C

  @property(nonatomic) CGFloat decelerationRate

  Discussion

  Your application can use the UIScrollViewDecelerationRateNormal and UIScrollViewDecelerationRateFast constants as reference points for reasonable deceleration rates.

  Availability

  Available in iOS 3.0 and later.

• dragging Property

  A Boolean value that indicates whether the user has begun scrolling the content. (read-only)

  Declaration

  SWIFT

  var dragging: Bool { get }

  OBJECTIVE-C

  @property(nonatomic, readonly, getter=isDragging) BOOL dragging

  Discussion

  The value held by this property might require some time or distance of scrolling before it is set to YES.

  Availability

  Available in iOS 2.0 and later.

  See Also

  tracking

• tracking Property

  Returns whether the user has touched the content to initiate scrolling. (read-only)

  Declaration

  SWIFT

  var tracking: Bool { get }

  OBJECTIVE-C

  @property(nonatomic, readonly, getter=isTracking) BOOL tracking

  Discussion

  The value of this property is YES if the user has touched the content view but might not have yet have started dragging it.

  Availability

  Available in iOS 2.0 and later.

  See Also

  dragging

• decelerating Property

  Returns whether the content is moving in the scroll view after the user lifted their finger. (read-only)

  Declaration

  SWIFT

  var decelerating: Bool { get }

  OBJECTIVE-C

  @property(nonatomic, readonly, getter=isDecelerating) BOOL decelerating

  Discussion

  The returned value is YES if user isn't dragging the content but scrolling is still occurring.

  Availability

  Available in iOS 2.0 and later.

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Managing the Scroll Indicator

• indicatorStyle Property

  The style of the scroll indicators. 

  Declaration

  SWIFT

  var indicatorStyle: UIScrollViewIndicatorStyle

  OBJECTIVE-C

  @property(nonatomic) UIScrollViewIndicatorStyle indicatorStyle

  Discussion

  The default style is UIScrollViewIndicatorStyleDefault. See Scroll Indicator Style for descriptions of these constants.

  Availability

  Available in iOS 2.0 and later.

• scrollIndicatorInsets Property

  The distance the scroll indicators are inset from the edge of the scroll view.

  Declaration

  SWIFT

  var scrollIndicatorInsets: UIEdgeInsets

  OBJECTIVE-C

  @property(nonatomic) UIEdgeInsets scrollIndicatorInsets

  Discussion

  The default value is UIEdgeInsetsZero. 

  Availability

  Available in iOS 2.0 and later.

• showsHorizontalScrollIndicator Property

  A Boolean value that controls whether the horizontal scroll indicator is visible.

  Declaration

  SWIFT

  var showsHorizontalScrollIndicator: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL showsHorizontalScrollIndicator

  Discussion

  The default value is YES. The indicator is visible while tracking is underway and fades out after tracking.

  Availability

  Available in iOS 2.0 and later.

• showsVerticalScrollIndicator Property

  A Boolean value that controls whether the vertical scroll indicator is visible.

  Declaration

  SWIFT

  var showsVerticalScrollIndicator: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL showsVerticalScrollIndicator

  Discussion

  The default value is YES. The indicator is visible while tracking is underway and fades out after tracking.

  Availability

  Available in iOS 2.0 and later.

• - flashScrollIndicators

  Displays the scroll indicators momentarily.

  Declaration

  SWIFT

  func flashScrollIndicators()

  OBJECTIVE-C

  - (void)flashScrollIndicators

  Discussion

  You should call this method whenever you bring the scroll view to front.

  Availability

  Available in iOS 2.0 and later.

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Zooming and Panning

• panGestureRecognizer Property

  The underlying gesture recognizer for pan gestures. (read-only)

  Declaration

  SWIFT

  var panGestureRecognizer: UIPanGestureRecognizer { get }

  OBJECTIVE-C

  @property(nonatomic, readonly) UIPanGestureRecognizer *panGestureRecognizer

  Discussion

  Your application accesses this property when it wants to more precisely control which pan gestures are recognized by the scroll view.

  Availability

  Available in iOS 5.0 and later.

• pinchGestureRecognizer Property

  The underlying gesture recognizer for pinch gestures. (read-only)

  Declaration

  SWIFT

  var pinchGestureRecognizer: UIPinchGestureRecognizer? { get }

  OBJECTIVE-C

  @property(nonatomic, readonly) UIPinchGestureRecognizer *pinchGestureRecognizer

  Discussion

  Your application accesses this property when it wants to more precisely control which pinch gestures are recognized by the scroll view.

  Availability

  Available in iOS 5.0 and later.

• - zoomToRect:animated:

  Zooms to a specific area of the content so that it is visible in the receiver.

  Declaration

  SWIFT

  func zoomToRect(_ rect: CGRect,
       animated animated: Bool)

  OBJECTIVE-C

  - (void)zoomToRect:(CGRect)rect
          animated:(BOOL)animated


  Parameters

  rect	A rectangle defining an area of the content view. The rectangle should be in the coordinate space of the view returned by viewForZoomingInScrollView:.
  animated	YES if the scrolling should be animated, NO if it should be immediate.

  Discussion

  This method zooms so that the content view becomes the area defined by rect, adjusting the zoomScale as necessary. 

  Availability

  Available in iOS 3.0 and later.

• zoomScale Property

  A floating-point value that specifies the current scale factor applied to the scroll view's content.

  Declaration

  SWIFT

  var zoomScale: CGFloat

  OBJECTIVE-C

  @property(nonatomic) CGFloat zoomScale

  Discussion

  This value determines how much the content is currently scaled. The default value is 1.0.

  Availability

  Available in iOS 3.0 and later.

• - setZoomScale:animated:

  A floating-point value that specifies the current zoom scale.

  Declaration

  SWIFT

  func setZoomScale(_ scale: CGFloat,
         animated animated: Bool)

  OBJECTIVE-C

  - (void)setZoomScale:(CGFloat)scale
            animated:(BOOL)animated


  Parameters

  scale	The new value to scale the content to.
  animated	YES to animate the transition to the new scale, NO to make the transition immediate.

  Discussion

  The new scale value should be between the minimumZoomScale and the maximumZoomScale.

  Availability

  Available in iOS 3.0 and later.

• maximumZoomScale Property

  A floating-point value that specifies the maximum scale factor that can be applied to the scroll view's content.

  Declaration

  SWIFT

  var maximumZoomScale: CGFloat

  OBJECTIVE-C

  @property(nonatomic) CGFloat maximumZoomScale

  Discussion

  This value determines how large the content can be scaled. It must be greater than the minimum zoom scale for zooming to be enabled. The default value is 1.0.

  Availability

  Available in iOS 2.0 and later.

  See Also

  minimumZoomScale
zoomBouncing
bouncesZoom
zoomBouncing
zooming

• minimumZoomScale Property

  A floating-point value that specifies the minimum scale factor that can be applied to the scroll view's content.

  Declaration

  SWIFT

  var minimumZoomScale: CGFloat

  OBJECTIVE-C

  @property(nonatomic) CGFloat minimumZoomScale

  Discussion

  This value determines how small the content can be scaled. The default value is 1.0

  Availability

  Available in iOS 2.0 and later.

  See Also

  maximumZoomScale
zoomBouncing
bouncesZoom
zoomBouncing
zooming

• zoomBouncing Property

  A Boolean value that indicates that zooming has exceeded the scaling limits specified for the receiver. (read-only)

  Declaration

  SWIFT

  var zoomBouncing: Bool { get }

  OBJECTIVE-C

  @property(nonatomic, readonly, getter=isZoomBouncing) BOOL zoomBouncing

  Discussion

  The value of this property is YES if the scroll view is zooming back to a minimum or maximum zoom scaling value; otherwise the value is NO .

  Availability

  Available in iOS 2.0 and later.

  See Also

  maximumZoomScale
minimumZoomScale
zooming
bouncesZoom

• zooming Property

  A Boolean value that indicates whether the content view is currently zooming in or out. (read-only)

  Declaration

  SWIFT

  var zooming: Bool { get }

  OBJECTIVE-C

  @property(nonatomic, readonly, getter=isZooming) BOOL zooming

  Discussion

  The value of this property is YES if user is making a zoom gesture, otherwise it is NO .

  Availability

  Available in iOS 2.0 and later.

  See Also

  maximumZoomScale
minimumZoomScale
zoomBouncing
bouncesZoom

• bouncesZoom Property

  A Boolean value that determines whether the scroll view animates the content scaling when the scaling exceeds the maximum or minimum limits.

  Declaration

  SWIFT

  var bouncesZoom: Bool

  OBJECTIVE-C

  @property(nonatomic) BOOL bouncesZoom

  Discussion

  If the value of this property is YES and zooming exceeds either the maximum or minimum limits for scaling, the scroll view temporarily animates the content scaling just past these limits before returning to them. If this property is NO, zooming stops immediately at one a scaling limits. The default is YES . 

  Availability

  Available in iOS 2.0 and later.

  See Also

  maximumZoomScale
minimumZoomScale
zoomBouncing
zooming

•  

   

   

   

Managing the Delegate

• delegate Property

  The delegate of the scroll-view object.

  Declaration

  SWIFT

  weak var delegate: UIScrollViewDelegate?

  OBJECTIVE-C

  @property(nonatomic, weak) id< UIScrollViewDelegate > delegate

  Discussion

  The delegate must adopt the UIScrollViewDelegate protocol. The UIScrollView class, which does not retain the delegate, invokes each protocol method the delegate implements.

  Availability

  Available in iOS 2.0 and later.

•  

   

   

   

Managing the Keyboard

• keyboardDismissMode Property

  The manner in which the keyboard is dismissed when a drag begins in the scroll view.

  Declaration

  SWIFT

  var keyboardDismissMode: UIScrollViewKeyboardDismissMode

  OBJECTIVE-C

  @property(nonatomic) UIScrollViewKeyboardDismissMode keyboardDismissMode

  Discussion

  See UIScrollViewKeyboardDismissMode for possible values. The default value is UIScrollViewKeyboardDismissModeNone.

  Availability

  Available in iOS 7.0 and later.

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Constants

• UIScrollViewIndicatorStyle

  The style of the scroll indicators. You use these constants to set the value of the indicatorStyle style.

  Declaration

  SWIFT

  enum UIScrollViewIndicatorStyle : Int { case Default case Black case White }

  OBJECTIVE-C

  typedef enum : NSInteger { UIScrollViewIndicatorStyleDefault, UIScrollViewIndicatorStyleBlack, UIScrollViewIndicatorStyleWhite } UIScrollViewIndicatorStyle;

  Constants

  • UIScrollViewIndicatorStyleDefault

    The default style of scroll indicator, which is black with a white border. This style is good against any content background. 

    Available in iOS 2.0 and later.

  • UIScrollViewIndicatorStyleBlack

    A style of indicator which is black and smaller than the default style. This style is good against a white content background.

    Available in iOS 2.0 and later.

  • UIScrollViewIndicatorStyleWhite

    A style of indicator is white and smaller than the default style. This style is good against a black content background.

    Available in iOS 2.0 and later.

  Import Statement

  OBJECTIVE-C

  @import UIKit;

  SWIFT

  import UIKit

  Availability

  Available in iOS 2.0 and later.

• Deceleration Constants

  The rate of deceleration for a scrolling view.

  Declaration

  SWIFT

  let UIScrollViewDecelerationRateNormal: CGFloat let UIScrollViewDecelerationRateFast: CGFloat

  OBJECTIVE-C

  const float UIScrollViewDecelerationRateNormal; const float UIScrollViewDecelerationRateFast;

  Constants

  • UIScrollViewDecelerationRateNormal

    The default deceleration rate for a scroll view.

    Available in iOS 3.0 and later.

  • UIScrollViewDecelerationRateFast

    A fast deceleration rate for a scroll view.

    Available in iOS 3.0 and later.

• UIScrollViewKeyboardDismissMode

  The manner in which the keyboard is dismissed when a drag begins in the scroll view.

  Declaration

  SWIFT

  enum UIScrollViewKeyboardDismissMode : Int { case None case OnDrag case Interactive }

  OBJECTIVE-C

  typedef enum : NSInteger { UIScrollViewKeyboardDismissModeNone, UIScrollViewKeyboardDismissModeOnDrag, UIScrollViewKeyboardDismissModeInteractive }UIScrollViewKeyboardDismissMode;

  Constants

  • UIScrollViewKeyboardDismissModeNone

    The keyboard does not get dismissed with a drag.

    Available in iOS 7.0 and later.

  • UIScrollViewKeyboardDismissModeOnDrag

    The keyboard is dismissed when a drag begins.

    Available in iOS 7.0 and later.

  • UIScrollViewKeyboardDismissModeInteractive

    The keyboard follows the dragging touch offscreen, and can be pulled upward again to cancel the dismiss.

    Available in iOS 7.0 and later.

  Import Statement

  OBJECTIVE-C

  @import UIKit;

  SWIFT

  import UIKit

  Availability

  Available in iOS 7.0 and later.