我正在努力实施一个＆＃34;消失＆＃34; url bar，当用户在webview中滚动时。
以下函数在- (void)scrollViewDidScroll:(UIScrollView *)scrollView中调用。
对于特定网页，该应用程序完全冻结并使用100％CPU。从反复试验中我们得出结论，删除CGAffineTransformScale修正了这个问题。我试图理解为什么会发生这种情况以及我如何实现相同的功能。
- (void)collapseQueryBox
{
_URLBarState = CLQURLBarStateCollapsing;
_queryBoxViewHeightConstraint.constant = COLLAPSED_QUERYBOX_HEIGHT;
[UIView animateWithDuration:COLLAPSE_ANIMATION_DURATION animations:^{
_webView.scrollView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0);
_queryLabel.transform = CGAffineTransformScale(_queryLabel.transform, COLLAPSE_ANIMATION_SCALE_FACTOR, COLLAPSE_ANIMATION_SCALE_FACTOR);
_queryLabel.layer.backgroundColor = [UIColor clearColor].CGColor;
[_browserContainerView layoutIfNeeded];
} completion:^(BOOL finished) {
_URLBarState = CLQURLBarStateCollapsed;
}];
}
处于冻结状态的已暂停应用的完整堆栈跟踪：
* thread #1: tid = 0xcbf9f, 0x025b40be libobjc.A.dylib`objc_msgSend + 26, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
* frame #0: 0x025b40be libobjc.A.dylib`objc_msgSend + 26
frame #1: 0x008cf411 Foundation`-[NSISEngine variableToWorkOnAmongVariablesWithIntegralizationViolationsIgnoringLostCauses:varsAlreadyAdjusted:] + 491
frame #2: 0x00a41ea3 Foundation`__44-[NSISEngine fixupIntegralizationViolations]_block_invoke + 1285
frame #3: 0x00a4368c Foundation`-[NSISEngine withBehaviors:performModifications:] + 107
frame #4: 0x008cf21a Foundation`-[NSISEngine withoutOptimizingAtEndRunBlockWithAutomaticOptimizationDisabled:] + 48
frame #5: 0x008cf1d9 Foundation`-[NSISEngine fixupIntegralizationViolations] + 96
frame #6: 0x008ceef8 Foundation`-[NSISEngine optimize] + 204
frame #7: 0x008d57e3 Foundation`-[NSISEngine constraintDidChangeSuchThatMarker:shouldBeReplacedByMarkerPlusDelta:] + 336
frame #8: 0x00a43e23 Foundation`-[NSISEngine tryToChangeConstraintSuchThatMarker:isReplacedByMarkerPlusDelta:undoHandler:] + 489
frame #9: 0x00a4b2d5 Foundation`-[NSLayoutConstraint _tryToChangeContainerGeometryWithUndoHandler:] + 578
frame #10: 0x008c8d4f Foundation`-[NSLayoutConstraint _setSymbolicConstant:constant:] + 384
frame #11: 0x008cb6a1 Foundation`-[NSLayoutConstraint setConstant:] + 52
frame #12: 0x00e398a5 UIKit`-[UIScrollView setContentSize:] + 566
frame #13: 0x01030a5a UIKit`-[UITableViewCell _updateWrapperContentInset] + 117
frame #14: 0x0103963a UIKit`-[UITableViewCell setFrame:] + 701
frame #15: 0x00e1b7b0 UIKit`-[UIView(Geometry) _applyAutoresizingMaskWithOldSuperviewSize:] + 840
frame #16: 0x00e1c552 UIKit`-[UIView(Geometry) _resizeWithOldSuperviewSize:] + 290
frame #17: 0x00e1c5aa UIKit`-[UIView(Geometry) resizeWithOldSuperviewSize:] + 80
frame #18: 0x00e1b185 UIKit`__46-[UIView(Geometry) resizeSubviewsWithOldSize:]_block_invoke + 87
frame #19: 0x028a1d86 CoreFoundation`__53-[__NSArrayM enumerateObjectsWithOptions:usingBlock:]_block_invoke + 102
frame #20: 0x028a1c5f CoreFoundation`-[__NSArrayM enumerateObjectsWithOptions:usingBlock:] + 239
frame #21: 0x00e1b115 UIKit`-[UIView(Geometry) resizeSubviewsWithOldSize:] + 149
frame #22: 0x00e19c4e UIKit`-[UIView(Geometry) setFrame:] + 559
frame #23: 0x00e1b7b0 UIKit`-[UIView(Geometry) _applyAutoresizingMaskWithOldSuperviewSize:] + 840
frame #24: 0x00e1c552 UIKit`-[UIView(Geometry) _resizeWithOldSuperviewSize:] + 290
frame #25: 0x00e1c5aa UIKit`-[UIView(Geometry) resizeWithOldSuperviewSize:] + 80
frame #26: 0x00e1b185 UIKit`__46-[UIView(Geometry) resizeSubviewsWithOldSize:]_block_invoke + 87
frame #27: 0x028a1d86 CoreFoundation`__53-[__NSArrayM enumerateObjectsWithOptions:usingBlock:]_block_invoke + 102
frame #28: 0x028a1c5f CoreFoundation`-[__NSArrayM enumerateObjectsWithOptions:usingBlock:] + 239
frame #29: 0x00e1b115 UIKit`-[UIView(Geometry) resizeSubviewsWithOldSize:] + 149
frame #30: 0x00eadc1a UIKit`-[UITableView resizeSubviewsWithOldSize:] + 98
frame #31: 0x00e1c819 UIKit`-[UIView(Geometry) setBounds:] + 510
frame #32: 0x00e39627 UIKit`-[UIScrollView setBounds:] + 1036
frame #33: 0x00eadf5f UIKit`-[UITableView setBounds:] + 260
frame #34: 0x00e1befd UIKit`-[UIView(Geometry) _applyISEngineLayoutValues] + 324
frame #35: 0x00e1c4c0 UIKit`-[UIView(Geometry) _resizeWithOldSuperviewSize:] + 144
frame #36: 0x00e457bb UIKit`-[UIScrollView _resizeWithOldSuperviewSize:] + 73
frame #37: 0x00e1c5aa UIKit`-[UIView(Geometry) resizeWithOldSuperviewSize:] + 80
frame #38: 0x00e1b185 UIKit`__46-[UIView(Geometry) resizeSubviewsWithOldSize:]_block_invoke + 87
frame #39: 0x028a1d86 CoreFoundation`__53-[__NSArrayM enumerateObjectsWithOptions:usingBlock:]_block_invoke + 102
frame #40: 0x028a1c5f CoreFoundation`-[__NSArrayM enumerateObjectsWithOptions:usingBlock:] + 239
frame #41: 0x00e1b115 UIKit`-[UIView(Geometry) resizeSubviewsWithOldSize:] + 149
frame #42: 0x0145961c UIKit`-[UIView(AdditionalLayoutSupport) _is_layout] + 158
frame #43: 0x00e20336 UIKit`-[UIView(Hierarchy) layoutSubviews] + 80
frame #44: 0x00e2d964 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
frame #45: 0x025b682b libobjc.A.dylib`-[NSObject performSelector:withObject:] + 70
frame #46: 0x01df345a QuartzCore`-[CALayer layoutSublayers] + 148
frame #47: 0x01de7244 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 380
frame #48: 0x01de70b0 QuartzCore`CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 26
frame #49: 0x01d4d7fa QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 294
frame #50: 0x01d4eb85 QuartzCore`CA::Transaction::commit() + 393
frame #51: 0x01d4f258 QuartzCore`CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 92
frame #52: 0x027ed36e CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
frame #53: 0x027ed2bf CoreFoundation`__CFRunLoopDoObservers + 399
frame #54: 0x027cb254 CoreFoundation`__CFRunLoopRun + 1076
frame #55: 0x027ca9d3 CoreFoundation`CFRunLoopRunSpecific + 467
frame #56: 0x027ca7eb CoreFoundation`CFRunLoopRunInMode + 123
frame #57: 0x041895ee GraphicsServices`GSEventRunModal + 192
frame #58: 0x0418942b GraphicsServices`GSEventRun + 104
frame #59: 0x00dbef9b UIKit`UIApplicationMain + 1225