iOS System KeyBoard 结构

UITextEffectsWindow {(0, 0), (320, 480)}
- UIPeripheralHostView {(0, 0), (320, 216)}
|- UIKBInputBackdropView
||- UIKBBackdropView
|||- _UIBackdropEffectView
|||- UIView
|||- UIView
||- UIKeyboardAutomatic
|||- UIKeyboardImpl
||||- UIKeyboardLayoutStar
|||||- UIBBackgroundView
||||||- UIImageView 
|||||- UIKBKeyplaneView
||||||- UIKBSplitImageView [Hiden]
||||||- UIKBSplitImageView ㈠
|||||||- UIImageView 
||||||- UIKBSplitImageView ㈡
|||||||- UIImageView
||||||- UIKBKeyView ㈢ [123]    {(1, 173), (38, 42)}  
||||||- UIKBKeyView ㈣ [globel] {(41, 173), (38, 42)}
||||||- UIKBKeyView ㈤ [space]  {(113, 173), (126, 42)}
||||||- UIKBKeyView ㈥ [voice]  {(81, 173), (30, 42)}
||||||- UIKBKeyView ㈦ [Send]   {(241, 173), (78, 42)}
||||||- UIKBKeyView ㈧ [shift]  {(1, 119), (40, 42)}
||||||- UIKBKeyView ㈨ [delete] {(279, 119), (40, 42)}
||- MMInputAccessoryView {(0, 0), (320, 0)}
|- UIKBBlurredKeyView {(-3, 206), (102, 114)}
||- UIBBackdropView {(0, 0), (102, 114)}
|||- _UIBackdropEffectView
|||- UIView
|||- UIView ㈩
||- UIBKeyView ⑪ {(0, 0), (102, 114)}

|- UIKBBlurredKeyView {(41, 206), (302, 114)}
||- UIBBackdropView {(0, 0), (302, 114)}
|||- _UIBackdropEffectView
|||- UIView
|||- UIView ⑫
||- UIBKeyView ⑬ {(0, 0), (302, 114)}