我很惭愧发布这个，但我变得绝望了。
对于AutoLayout，我是一个菜鸟。这主要是因为我的应用程序中有近60个不同的屏幕。为什么改变什么工作？无论如何，我不使用XIB / NIB / Storyboard，因为任何时候我需要在应用程序范围内进行UI更改，我必须解决一些问题。相反，我有自己的一套UIViewController子类。其中一个只是像UITableViewController一样有一个UITableView。我可以在睡梦中制作出UITableViews。
我有一个新的屏幕，需要在表格视图的标题内有几个按钮。我正试图通过AutoLayout变得更好，所以我尽量使用它。没有进一步的叙述，这是一个非常简短的自成一体的例子。
#import "AppDelegate.h"
@interface TestViewController : UIViewController<UITableViewDataSource, UITableViewDelegate>
@property (nonatomic, strong) NSArray *rows;
@end
@implementation TestViewController
- (void) loadView {
UITableView *tv = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] bounds] style:UITableViewStyleGrouped];
[tv setAutoresizingMask:UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth];
[tv setDelegate:self];
[tv setDataSource:self];
[self setView:tv];
UIView *tableHeader = [[UIView alloc] init];
[tableHeader setTranslatesAutoresizingMaskIntoConstraints:NO];
[tv setTableHeaderView:tableHeader];
UIButton *selectProfileButton = [UIButton buttonWithType:UIButtonTypeCustom];
[selectProfileButton setTranslatesAutoresizingMaskIntoConstraints:NO];
[selectProfileButton setShowsTouchWhenHighlighted:YES];
[selectProfileButton setTitle:@"Select Profile..." forState:UIControlStateNormal];
[tableHeader addSubview:selectProfileButton];
UIButton *editProfileButton = [UIButton buttonWithType:UIButtonTypeCustom];
[editProfileButton setTranslatesAutoresizingMaskIntoConstraints:NO];
[editProfileButton setImage:[UIImage imageNamed:@"EditAccessoryIcon"] forState:UIControlStateNormal];
[tableHeader addSubview:editProfileButton];
UIEdgeInsets padding = UIEdgeInsetsMake(5, 10, 5, 5);
// select button in NW corner
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:selectProfileButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeTop multiplier:1.0 constant:padding.top]];
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:selectProfileButton attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeLeft multiplier:1.0 constant:padding.left]];
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:selectProfileButton attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-padding.bottom]];
// edit button in NE corner
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:editProfileButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeTop multiplier:1.0 constant:padding.top]];
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:editProfileButton attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeRight multiplier:1.0 constant:-padding.right]];
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:editProfileButton attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual
toItem:tableHeader attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-padding.bottom]];
// spacing between buttons
[tableHeader addConstraint:[NSLayoutConstraint constraintWithItem:selectProfileButton attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual
toItem:editProfileButton attribute:NSLayoutAttributeLeft multiplier:1.0 constant:-10.0]];
}
- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [[self rows] count]; }
- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"];
[cell setSelectionStyle:UITableViewCellSelectionStyleNone];
}
[[cell textLabel] setText:[[self rows] objectAtIndex:[indexPath row]]];
return cell;
}
@end
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
TestViewController *test = [[TestViewController alloc] init];
[test setRows:@[@"1", @"2", @"3"]];
[[self window] setRootViewController:test];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
@end
不幸的是，在运行时我得到了这个：
2014-07-11 13:18:48.502 TestTableHeader[9478:60b] *** Assertion failure in -[UITableView layoutSublayersOfLayer:], /SourceCache/UIKit_Sim/UIKit-2935.137/UIView.m:8794
2014-07-11 13:18:48.505 TestTableHeader[9478:60b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Auto Layout still required after executing -layoutSubviews. UITableView's implementation of -layoutSubviews needs to call super.'
*** First throw call stack:
(
0 CoreFoundation 0x017ed1e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x0156c8e5 objc_exception_throw + 44
2 CoreFoundation 0x017ed048 +[NSException raise:format:arguments:] + 136
3 Foundation 0x0114c4de -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 116
4 UIKit 0x0029ba38 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 567
5 libobjc.A.dylib 0x0157e82b -[NSObject performSelector:withObject:] + 70
6 QuartzCore 0x03c5845a -[CALayer layoutSublayers] + 148
7 QuartzCore 0x03c4c244 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
8 QuartzCore 0x03c583a5 -[CALayer layoutIfNeeded] + 160
9 UIKit 0x0035dae3 -[UIViewController window:setupWithInterfaceOrientation:] + 304
10 UIKit 0x00273aa7 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] + 5212
11 UIKit 0x00272646 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:] + 82
12 UIKit 0x00272518 -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] + 117
13 UIKit 0x002725a0 -[UIWindow _setRotatableViewOrientation:duration:force:] + 67
14 UIKit 0x0027163a __57-[UIWindow _updateToInterfaceOrientation:duration:force:]_block_invoke + 120
15 UIKit 0x0027159c -[UIWindow _updateToInterfaceOrientation:duration:force:] + 400
16 UIKit 0x002722f3 -[UIWindow setAutorotates:forceUpdateInterfaceOrientation:] + 870
17 UIKit 0x002758e6 -[UIWindow setDelegate:] + 449
18 UIKit 0x0034fb77 -[UIViewController _tryBecomeRootViewControllerInWindow:] + 180
19 UIKit 0x0026b474 -[UIWindow addRootViewControllerViewIfPossible] + 591
20 UIKit 0x0026b5ef -[UIWindow _setHidden:forced:] + 312
21 UIKit 0x0026b86b -[UIWindow _orderFrontWithoutMakingKey] + 49
22 UIKit 0x002763c8 -[UIWindow makeKeyAndVisible] + 65
23 TestTableHeader 0x00002dfa -[AppDelegate application:didFinishLaunchingWithOptions:] + 890
24 UIKit 0x0022614f -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 309
25 UIKit 0x00226aa1 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1810
26 UIKit 0x0022b667 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
27 UIKit 0x0023ff92 -[UIApplication handleEvent:withNewEvent:] + 3517
28 UIKit 0x00240555 -[UIApplication sendEvent:] + 85
29 UIKit 0x0022d250 _UIApplicationHandleEvent + 683
30 GraphicsServices 0x037e2f02 _PurpleEventCallback + 776
31 GraphicsServices 0x037e2a0d PurpleEventCallback + 46
32 CoreFoundation 0x01768ca5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
33 CoreFoundation 0x017689db __CFRunLoopDoSource1 + 523
34 CoreFoundation 0x0179368c __CFRunLoopRun + 2156
35 CoreFoundation 0x017929d3 CFRunLoopRunSpecific + 467
36 CoreFoundation 0x017927eb CFRunLoopRunInMode + 123
37 UIKit 0x0022ad9c -[UIApplication _run] + 840
38 UIKit 0x0022cf9b UIApplicationMain + 1225
39 TestTableHeader 0x00002fed main + 141
40 libdyld.dylib 0x01e34701 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
从我读过的内容来看，这意味着我错过了一个约束。 UIButtons具有固有的大小，所以我只需要设置它们的位置。容器UIView将由UITableView调整大小，因此没有任何关系。 （我甚至尝试设置咯咯的高度 - 我没有傻笑。）
我搞砸了哪里？
谢谢！
更新了示例代码和堆栈，以提供简短的自包含示例。
答案 0 :(得分：2)
我遇到了同样的问题。我认为这不是因缺少约束而引起的。这是因为UITableView显然没有正确处理自动布局的页眉/页脚。适用于我的解决方法是使用systemLayoutSizeFittingSize:方法设置框架：
//initialize tableHeader, add subviews and constraints
CGSize size = [tableHeader systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
tableHeader.frame = (CGRect){.origin = CGPointZero, .size = size};
self.tableView.tableHeaderView = tableHeader;
请注意，我没有将translatesAutoresizingMaskIntoConstraints设置为NO。
此外，您似乎还没有添加所有必需的限制。您只需定位按钮，但您的tableHeader不知道如何计算其自己的宽度和高度。您可能需要将selectProfileButton（或其他按钮的）底部等于tableHeader的底部，并在按钮之间添加（最小）水平间距。
另外，据我记忆，无论有什么限制，UITableView都会将tableHeader的宽度扩展到自己的宽度。