UIView: Difference between revisions

Revision as of 09:43, 28 November 2009

UIView is the root class of all UI elements.

Getting View Hierarchy Info

There are 2 ways of getting the view hierarchy info, the "human readable" -[UIView recursiveDescription] and "machine readable" -[UIView scriptingInfoWithChildren].

-recursiveDescription

Available in	3.0 – 3.1
Signature	`-(NSString*)recursiveDescription;`

Returns the description of the view and its subviews.

Example output:

<UIWebView: 0x4116bb0; frame = (0 100; 320 230); layer = <CALayer: 0x4116c20>>
   <UIScroller: 0x411e110; frame = (0 0; 320 230); clipsToBounds = YES; autoresize = H; layer = <CALayer: 0x411e4d0>>
       <UIImageView: 0x411f460; frame = (0 0; 54 54); transform = [-1, 0, -0, -1, 0, 0]; alpha = 0; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x411f490>>
       <UIWebDocumentView: 0x4812c00; frame = (0 0; 320 230); layer = <UIWebLayer: 0x41171c0>>

-scriptingInfoWithChildren

Available in	2.0 – 3.1
Signature	`-(NSDictionary*)scriptingInfoWithChildren;`

This function returns an NSDictionary with contains some information e.g. geometry, class name, etc.

Animation Blocks

Further information: UIViewAnimationState

Animation blocks are implemented by the UIViewAnimationState class with the following correspondences:

UIView methods	Equivalent call
`[UIView beginAnimations:`identifier `context:`context`];`	`[UIViewAnimationState pushViewAnimationState:`identifier `context:`context`];`
`[UIView commitAnimations];`	`[UIViewAnimationState popAnimationState];`
`[UIView setAnimationStartDate:`date`];`	`__currentViewAnimationState->_start = [`date `timeIntervalSinceReferenceDate];`
`[UIView setAnimationsEnabled:`enabled`];`	`__animate =` enabled`;`
`[UIView setAnimationDelegate:`delegate`];`	`if (__currentViewAnimationState->_delegate !=` delegate`) { [__currentViewAnimationState->_delegate release]; __currentViewAnimationState->_delegate = [`delegate`retain]; }`
`[UIView setAnimationWillStartSelector:`selector`];`	`__currentViewAnimationState->_willStartSelector =` selector`;`
`[UIView setAnimationDidStopSelector:`selector`];`	`__currentViewAnimationState->_didEndSelector =` selector`;`
`[UIView setAnimationDuration:`duration`];`	`__currentViewAnimationState->_duration =` duration`;`
`[UIView setAnimationDelay:`delay`];`	`__currentViewAnimationState->_delay =` delay`;`
`[UIView setAnimationCurve:`curve`];`	`__currentViewAnimationState->_curve =` curve`;`
`[UIView setAnimationRepeatCount:`repeatCount`];`	`__currentViewAnimationState->_repeatCount =` repeatCount`;`
`[UIView setAnimationRepeatAutoreverses:`autoreverses`];`	`__currentViewAnimationState->_autoreverses =` autoreverses`;`
`[UIView setAnimationBeginsFromCurrentState:`value`];`	`__currentViewAnimationState->_useCurrentLayerState =` value`;`
`[UIView setAnimationTransition:`transVal `forView:`container `cache:`cache`];`	`__currentViewAnimationState->_transition =` transVal`; __currentViewAnimationState->_transitionView = [`container`retain]; __currentViewAnimationState->_cacheTransition =`cache`;`
`[UIView areAnimationsEnabled];`	`__animate;`

In above, __currentViewAnimationState is a global variable, which is a UIViewAnimationState. This value is automatically updated after calling +pushViewAnimationState:context: and +popAnimationState. NULL checks were omitted in the above codes for simplicity.

There are also a few undocumented methods:

UIView method	Equivalent call
`[UIView beginAnimations:`identifier`];`	`[UIView beginAnimations:`identifier `context:NULL];`
`[UIView _pendingAnimations];`	`__currentViewAnimationState != nil;`
`[UIView setAnimationPosition:`position`];`	`__currentViewAnimationState->_position =` position`;`
`[UIView disableAnimation];`	`__animate = NO;`
`[UIView enableAnimation];`	`__animate = YES;`
`[UIView setAnimationFrameInterval:`interval`];`	`__currentViewAnimationState->_frameInterval =` interval`;`
`[UIView setAnimationStartTime:`time`];`	`__currentViewAnimationState->_start =` time`;`
`[UIView setAnimationRoundsToInteger:`rounds`];`	`__currentViewAnimationState->_roundsToInteger =` rounds`;`

There are also a few equivalent (probably deprecated) selectors:

+endAnimations = +commitAnimations
+setAnimationAutoreverses: = +setAnimationRepeatAutoreverses:
+setAnimationFromCurrentState: = +setAnimationBeginsFromCurrentState:

frame and bounds

frame and bounds are both properties of a UIView. When the view's transform is not identity, the only difference between them is the origin of bounds is always zero.

When transform is not identity, the SDK documentation warns that frame is undefined:

“ Warning: If the transform property is not the identity transform, the value of this property is undefined and therefore should be ignored. ”

but this is not completely true — the frame is actually the rectangle enclosing the transformed view.

These properties are actually proxies to the corresponding ones of CALayer. However, while the bounds (and center) is an internal property, frame incurs a transactional lock (spin lock) and an affine transform.

References

Official documentation: UIView
Header: http://github.com/kennytm/iphone-private-frameworks/blob/master/UIKit/UIView2.h

@@ Line 125: / Line 125: @@
 but this is not completely true — the <tt>frame</tt> is actually the rectangle enclosing the ''transformed'' view.
-These properties are actually proxies to the corresponding ones of [[CALayer]]. However, while the <tt>bounds</tt> (and <tt>center</tt>) is an internal property, <tt>frame</tt> incurs a transactional lock and an affine transform.
+These properties are actually proxies to the corresponding ones of [[CALayer]]. However, while the <tt>bounds</tt> (and <tt>center</tt>) is an internal property, <tt>frame</tt> incurs a transactional lock (spin lock) and an affine transform.
 == References ==
 * Official documentation: {{sdklink|UIKit|UIView}}
 {{IPFHeader|UIKit|3=2}}