iOS AutoLayout問題：無法同時滿足約束

Question

腳步：

1. 我在一個頁面中有兩個tableview，但是一次只顯示一個tableView。
2. 我為tableview的標題視圖創建了一個視圖（稱為headerView ）；
3. 我將當前tableView（A）的headerView設置為tableHeaderView，將另一個tableView（B）的nil設置為tableHeaderView（show A）;
4. 我單擊一個按鈕以顯示tableView（B），因此將nil設置為tableView（A）的tableHeaderView，將headerView設置為tableView（B）的tableHeaderView。

當我為tableView（N）設置headerView時，錯誤即將來臨，詳細信息請查看以下日志。 控制台錯誤日志如下：

    2015-12-04 10:15:18.777 XXXApp[1223:360705] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x7f8f7bdd74b0 H:|-(10)-[UIView:0x7f8f7bdbbe00]   (Names: '|':MarketGoodsDetail:0x7f8f7bdb92d0 )>",
    "<NSLayoutConstraint:0x7f8f7bdd7500 H:[UIView:0x7f8f7bdbbe00]-(10)-|   (Names: '|':MarketGoodsDetail:0x7f8f7bdb92d0 )>",
    "<NSLayoutConstraint:0x7f8f7bdd8fa0 H:|-(0)-[MarketGoodsDetail:0x7f8f7bdb92d0]   (Names: '|':UIView:0x7f8f7bdd8b70 )>",
    "<NSLayoutConstraint:0x7f8f7bdd8ff0 H:[MarketGoodsDetail:0x7f8f7bdb92d0]-(0)-|   (Names: '|':UIView:0x7f8f7bdd8b70 )>",
    "<NSLayoutConstraint:0x7f8f7bddac40 H:[UIView:0x7f8f7bdd8b70]-(0)-|   (Names: '|':UIView:0x7f8f7bdda860 )>",
    "<NSLayoutConstraint:0x7f8f7bddace0 H:|-(0)-[UIView:0x7f8f7bdd8b70]   (Names: '|':UIView:0x7f8f7bdda860 )>",
    "<NSLayoutConstraint:0x7f8f7e0c6d90 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7f8f7bdda860(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f8f7bdd7500 H:[UIView:0x7f8f7bdbbe00]-(10)-|   (Names: '|':MarketGoodsDetail:0x7f8f7bdb92d0 )>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

當Jason Jarrett的博客http://staxmanade.com/2015/06/debugging-ios-autolayout-issues/時，我打印了該視圖的自動布局信息，我認為它引起了以下問題：

po [0x7f8f7bdb92d0 recursiveDescription]
<MarketGoodsDetail: 0x7f8f7bdb92d0; frame = (0 0; 375 127); autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x7f8f7bdb9760>>
   | <UILabel: 0x7f8f7bdb9b80; frame = (10 8.5; 37.5 12); text = '(廣貴所)'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdb9780>>
   |    | <_UILabelContentLayer: 0x7f8f7bfc4090> (layer)
   | <UILabel: 0x7f8f7bdba820; frame = (10 22.5; 121.5 36); text = '2892.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdb9f10>>
   | <UILabel: 0x7f8f7bdbb460; frame = (237.5 35; 52.5 20.5); text = '-13.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbb660>>
   | <UILabel: 0x7f8f7bdbb9c0; frame = (307 35; 58 20.5); text = '-0.45%'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbbbc0>>
   | <UIView: 0x7f8f7bdbbe00; frame = (10 63.5; 355 0.5); autoresize = RM+BM; layer = <CALayer: 0x7f8f7bdbbf70>>
   | <UILabel: 0x7f8f7bdbc0b0; frame = (10 76; 26 16); text = '今開'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbc2b0>>
   |    | <_UILabelContentLayer: 0x7f8f7e0c2a90> (layer)
   | <UILabel: 0x7f8f7bdbcd70; frame = (42 76; 51.5 16); text = '2905.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbcf70>>
   | <UILabel: 0x7f8f7bdbd180; frame = (10 102; 26 16); text = '昨收'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbd380>>
   |    | <_UILabelContentLayer: 0x7f8f7e0c1640> (layer)
   | <UILabel: 0x7f8f7bdbd590; frame = (42 102; 51.5 16); text = '2905.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbd790>>
   | <UILabel: 0x7f8f7bdbd9a0; frame = (281.5 76; 26 16); text = '最高'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbdba0>>
   |    | <_UILabelContentLayer: 0x7f8f7e0c1ea0> (layer)
   | <UILabel: 0x7f8f7bdbddb0; frame = (313.5 76; 51.5 16); text = '2909.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbdfb0>>
   | <UILabel: 0x7f8f7bdbe1c0; frame = (281.5 102; 26 16); text = '最低'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbe3c0>>
   |    | <_UILabelContentLayer: 0x7f8f7e0c4e60> (layer)
   | <UILabel: 0x7f8f7bdbe5d0; frame = (313.5 102; 51.5 16); text = '2889.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbe7d0>>
   | <UIView: 0x7f8f7bdbe9e0; frame = (146 76; 83.5 42); autoresize = RM+BM; layer = <CALayer: 0x7f8f7bdbeb50>>
   |    | <UILabel: 0x7f8f7bdbeb70; frame = (0 0; 26 16); text = '買進'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbed70>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c4e90> (layer)
   |    | <UILabel: 0x7f8f7bdbef80; frame = (0 26; 26 16); text = '賣出'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd5990>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c4b70> (layer)
   |    | <UILabel: 0x7f8f7bdd5b80; frame = (32 0; 51.5 16); text = '2898.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd5d80>>
   |    | <UILabel: 0x7f8f7bdd5f90; frame = (32 26; 51.5 16); text = '2892.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd6190>>

它是超級視圖自動布局：

po [[0x7f8f7bdb92d0 superview] recursiveDescription]
<UIView: 0x7f8f7bdd8b70; frame = (0 0; 375 127); autoresize = RM+BM; layer = <CALayer: 0x7f8f7bdd8ce0>>
   | <MarketGoodsDetail: 0x7f8f7bdb92d0; frame = (0 0; 375 127); autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x7f8f7bdb9760>>
   |    | <UILabel: 0x7f8f7bdb9b80; frame = (10 8.5; 37.5 12); text = '(廣貴所)'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdb9780>>
   |    |    | <_UILabelContentLayer: 0x7f8f7bfc4090> (layer)
   |    | <UILabel: 0x7f8f7bdba820; frame = (10 22.5; 121.5 36); text = '2892.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdb9f10>>
   |    | <UILabel: 0x7f8f7bdbb460; frame = (237.5 35; 52.5 20.5); text = '-13.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbb660>>
   |    | <UILabel: 0x7f8f7bdbb9c0; frame = (307 35; 58 20.5); text = '-0.45%'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbbbc0>>
   |    | <UIView: 0x7f8f7bdbbe00; frame = (10 63.5; 355 0.5); autoresize = RM+BM; layer = <CALayer: 0x7f8f7bdbbf70>>
   |    | <UILabel: 0x7f8f7bdbc0b0; frame = (10 76; 26 16); text = '今開'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbc2b0>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c2a90> (layer)
   |    | <UILabel: 0x7f8f7bdbcd70; frame = (42 76; 51.5 16); text = '2905.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbcf70>>
   |    | <UILabel: 0x7f8f7bdbd180; frame = (10 102; 26 16); text = '昨收'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbd380>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c1640> (layer)
   |    | <UILabel: 0x7f8f7bdbd590; frame = (42 102; 51.5 16); text = '2905.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbd790>>
   |    | <UILabel: 0x7f8f7bdbd9a0; frame = (281.5 76; 26 16); text = '最高'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbdba0>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c1ea0> (layer)
   |    | <UILabel: 0x7f8f7bdbddb0; frame = (313.5 76; 51.5 16); text = '2909.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbdfb0>>
   |    | <UILabel: 0x7f8f7bdbe1c0; frame = (281.5 102; 26 16); text = '最低'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbe3c0>>
   |    |    | <_UILabelContentLayer: 0x7f8f7e0c4e60> (layer)
   |    | <UILabel: 0x7f8f7bdbe5d0; frame = (313.5 102; 51.5 16); text = '2889.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbe7d0>>
   |    | <UIView: 0x7f8f7bdbe9e0; frame = (146 76; 83.5 42); autoresize = RM+BM; layer = <CALayer: 0x7f8f7bdbeb50>>
   |    |    | <UILabel: 0x7f8f7bdbeb70; frame = (0 0; 26 16); text = '買進'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdbed70>>
   |    |    |    | <_UILabelContentLayer: 0x7f8f7e0c4e90> (layer)
   |    |    | <UILabel: 0x7f8f7bdbef80; frame = (0 26; 26 16); text = '賣出'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd5990>>
   |    |    |    | <_UILabelContentLayer: 0x7f8f7e0c4b70> (layer)
   |    |    | <UILabel: 0x7f8f7bdd5b80; frame = (32 0; 51.5 16); text = '2898.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd5d80>>
   |    |    | <UILabel: 0x7f8f7bdd5f90; frame = (32 26; 51.5 16); text = '2892.00'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7f8f7bdd6190>>

誰能告訴我哪個約束導致了此問題？ 感謝您的幫助！

Answer 1

我認為您要將這些約束的優先級設置為999：

"<NSLayoutConstraint:0x7f8f7bdd74b0 H:|-(10)-[UIView:0x7f8f7bdbbe00]   (Names: '|':MarketGoodsDetail:0x7f8f7bdb92d0 )>",
"<NSLayoutConstraint:0x7f8f7bdd7500 H:[UIView:0x7f8f7bdbbe00]-(10)-|   (Names: '|':MarketGoodsDetail:0x7f8f7bdb92d0 )>"

我認為這些與以下內容沖突：

"<NSLayoutConstraint:0x7f8f7e0c6d90 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7f8f7bdda860(0)]>"

它指定您的容器視圖的寬度將為0點。 因此，它不能添加10個點的邊距（以上兩個約束要求該點）。 將它們設置為999應該可以優雅地覆蓋它們。

請參閱什么是“ UIView-Encapsulated-Layout-Width”約束？ 有關更多信息。