iphone - 如何在 self.view 的属性上设置 lldb 观察点？

Question

我想跟踪 self.view 的大小何时发生变化。正确的格式是什么？

(lldb) po self.view
(UIView *) $1 = 0x0a8aba20 <UIView: 0xa8aba20; frame = (0 0; 480 864); autoresize = W+TM+BM; layer = <CALayer: 0xa8aba50>>
(lldb) watch set variable self.view.frame.size.width
error: "self" is a pointer and . was used to attempt to access "view". Did you mean "self->view.frame.size.width"?
(lldb) watch set variable self->view
error: "view" is not a member of "(PlayViewController *) self"
(lldb) watch set variable self->view.frame.size.width
error: "view" is not a member of "(PlayViewController *) self"

我已经尝试了文档和其他 lldb 观察点问题，但找不到针对此特定案例的任何内容。

感谢您的帮助。

Answer 1

View Controller 从它的 _view 实例变量引用它的 View 。

View 不直接存储它的框架。它只是返回其图层的“框架”。

View 从它的 _layer 实例变量引用它的层。

图层也不存储帧。它根据其 bounds、position、anchorPoint 和 transform 计算其框架。大小是 bounds 的一部分。

图层不直接将其边界存储在实例变量中。相反，它的 layer 实例变量引用私有(private) C++ 类 CA::Layer 的实例。此类的成员布局未记录。

换句话说，你可以去 self->_view->_layer->layer 去到 CA::Layer 实例，但是你会卡住因为您不知道在 CA::Layer 的哪个位置可以找到边界。

因此，尝试使用观察点来检测 View 大小的变化是相当困难的。

在-[CALayer setBounds:]上打断点更容易。

在模拟器上

请记住在断点条件中使用层地址，而不是 View 地址。

(lldb) po self.view
(UIView *) $1 = 0x0a034690 <UIView: 0xa034690; frame = (0 20; 768 1004); autoresize = W+H; layer = <CALayer: 0xa034780>>
(lldb) break set -F '-[CALayer setBounds:]' -c '((int*)$esp)[1] == 0xa034780'
Breakpoint created: 2: name = '-[CALayer setBounds:]', locations = 1, resolved = 1

当命中断点时，CALayer实例被((int *)$esp)[1]引用，新的边界是* (CGRect *)($esp+12):

(lldb) po ((int*)$esp)[1]
(int) $8 = 167987072 <CALayer:0xa034780; position = CGPoint (384 480); bounds = CGRect (0 0; 768 1004); delegate = <UIView: 0xa034690; frame = (0 -22; 768 1004); autoresize = W+H; layer = <CALayer: 0xa034780>>; sublayers = (<CALayer: 0xa033010>); backgroundColor = <CGColor 0xa034960> [<CGColorSpace 0xa02b3b0> (kCGColorSpaceDeviceRGB)] ( 1 1 1 1 )>
(lldb) p *(CGRect*)($esp+12)
(CGRect) $9 = origin=(x=0, y=0) size=(width=768, height=960)
(lldb) finish
(lldb) po 0xa034780
(int) $10 = 167987072 <CALayer:0xa034780; position = CGPoint (384 480); bounds = CGRect (0 0; 768 960); delegate = <UIView: 0xa034690; frame = (0 0; 768 960); autoresize = W+H; layer = <CALayer: 0xa034780>>; sublayers = (<CALayer: 0xa033010>); backgroundColor = <CGColor 0xa034960> [<CGColorSpace 0xa02b3b0> (kCGColorSpaceDeviceRGB)] ( 1 1 1 1 )>

在设备上

请记住在断点条件中使用层地址，而不是 View 地址。

(lldb) po self.view
(UIView *) $0 = 0x1f031a10 <UIView: 0x1f031a10; frame = (0 20; 768 1004); autoresize = W+H; layer = <CALayer: 0x1f031b00>>
(lldb) break set -F '-[CALayer setBounds:]' -c '$r0 == 0x1f031b00'
Breakpoint created: 2: name = '-[CALayer setBounds:]', locations = 1, resolved = 1

当命中断点时，CALayer实例被$r0引用，新的X原点在$r2，新的Y 原点在 $r3，新尺寸为 *(CGSize *)$sp:

(lldb) po $r0
(unsigned int) $7 = 520297216 <CALayer:0x1f031b00; position = CGPoint (384 480); bounds = CGRect (0 0; 768 1004); delegate = <UIView: 0x1f031a10; frame = (0 -22; 768 1004); autoresize = W+H; layer = <CALayer: 0x1f031b00>>; sublayers = (<CALayer: 0x1f030840>); backgroundColor = <CGColor 0x1f031ce0> [<CGColorSpace 0x1e530ad0> (kCGColorSpaceDeviceRGB)] ( 1 1 1 1 )>
(lldb) p/f $r2
(unsigned int) $14 = 0
(lldb) p/f $r3
(unsigned int) $15 = 0
(lldb) p *(CGSize *)$sp
(CGSize) $16 = (width=768, height=960)
(lldb) finish
(lldb) po 0x1f031b00
(int) $17 = 520297216 <CALayer:0x1f031b00; position = CGPoint (384 480); bounds = CGRect (0 0; 768 960); delegate = <UIView: 0x1f031a10; frame = (0 0; 768 960); autoresize = W+H; layer = <CALayer: 0x1f031b00>>; sublayers = (<CALayer: 0x1f030840>); backgroundColor = <CGColor 0x1f031ce0> [<CGColorSpace 0x1e530ad0> (kCGColorSpaceDeviceRGB)] ( 1 1 1 1 )>