支持iOS 6/6 Plus的时候碰到这样一个问题：
塞在UITableViewCell里的UIPageControl居中设置失败了，偏右
刚刚设置时下断点查看(6Plus模拟器)：
<GrayPageControl: 0x7f96a535c350; baseClass = UIPageControl; frame = (179.5 241.75; 55 6); autoresize = W; layer = <CALayer: 0x7f96a535c4a0>>
运行后：
<GrayPageControl: 0x7f96a535c350; baseClass = UIPageControl; frame = (179.333 241.75; 149 6); autoresize = W; layer = <CALayer: 0x7f96a535c4a0>>
好奇在什么时候被改变的，考虑搞个内存修改断点，上lldb，听从忠告检测CALayer的frame改动而不是UIView的：
(lldb) po pc
<GrayPageControl: 0x15fe26ca0; baseClass = UIPageControl; frame = (160 217.375; 55 6); autoresize = W; layer = <CALayer: 0x174c38500>>
(lldb) break set -F '-[CALayer setBounds:]' -c '$x0 == 0x174c38500'
Breakpoint 113: where = QuartzCore`-[CALayer setBounds:], address = 0x000000018a3eb93c
结果是 layoutSubviews:
#0 0x000000018a3eb93c in -[CALayer setBounds:] () #1 0x000000018a3ec684 in -[CALayer setFrame:] () #2 0x000000018aa9da3c in -[UIView(Geometry) setFrame:] () #3 0x000000018aaba7b4 in -[UIView(Geometry) _applyAutoresizingMaskWithOldSuperviewSize:] () #4 0x000000018618cfc8 in __53-[__NSArrayM enumerateObjectsWithOptions:usingBlock:]_block_invoke () #5 0x000000018618ce6c in -[__NSArrayM enumerateObjectsWithOptions:usingBlock:] () #6 0x000000018aaa9f58 in -[UIView(Geometry) resizeSubviewsWithOldSize:] () #7 0x000000018aa9daf4 in -[UIView(Geometry) setFrame:] () #8 0x000000018ab7b9d4 in -[UITableViewCellContentView setFrame:] () #9 0x000000018abe442c in __53-[UITableView _configureCellForDisplay:forIndexPath:]_block_invoke () #10 0x000000018aab24c8 in +[UIView(Animation) performWithoutAnimation:] () #11 0x000000018abe3b0c in -[UITableView _configureCellForDisplay:forIndexPath:] () #12 0x000000018ad9b4d8 in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] () #13 0x000000018ad9006c in -[UITableView _updateVisibleCellsNow:isRecursive:] () #14 0x000000018ab84c44 in -[UITableView layoutSubviews] () #15 0x000000018aaa14a4 in -[UIView(CALayerDelegate) layoutSublayersOfLayer:] () #16 0x000000018a3f57a8 in -[CALayer layoutSublayers] () #17 0x000000018a3f0378 in CA::Layer::layout_if_needed(CA::Transaction*) () #18 0x000000018a3f021c in CA::Layer::layout_and_display_if_needed(CA::Transaction*) () #19 0x000000018a3efa14 in CA::Context::commit_transaction(CA::Transaction*) () #20 0x000000018a3ef798 in CA::Transaction::commit() () #21 0x000000018a3e91c8 in CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) () #22 0x000000018624ed98 in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ () #23 0x000000018624bd24 in __CFRunLoopDoObservers () #24 0x000000018624c104 in __CFRunLoopRun () #25 0x00000001861791f4 in CFRunLoopRunSpecific () #26 0x000000018f59b6fc in GSEventRunModal () #27 0x000000018ab0a10c in UIApplicationMain () #28 0x0000000100029ce0 in main |
