问题
So I'm new to the constraints.
I've a nib file which contains multiple Views as siblings. The ViewController's view contains a tableView and I've another view which is going to be added to the tableHeaderView (let's call it self.tableHeaderView).
The problem i'm facing is that I want to resize the self.tableHeaderView based on certain conditions. I've added constraints to all of my UI elements and I can't, for whatever reason, add a height constraint to the self.tableHeaderView via the nib.
I tried changing the frame of the self.tableHeaderView programmatically but that has no effect when i run the code in simulator, which makes sense because if I use Auto-layout, it should ignore the frame changes.
I tried adding a height constraint programmatically but it crashes.
This is the piece of code I've to add the height constraint.
[self.tableHeaderView addConstraint:[NSLayoutConstraint constraintWithItem:self.tableHeaderView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:107.0f]];
The exception i got: *** Assertion failure in -[UITableView layoutSublayersOfLayer:], /SourceCache/UIKit_Sim/UIKit-2903.2/UIView.m:8536
* Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Auto Layout still required after executing -layoutSubviews. UITableView's implementation of -layoutSubviews needs to call super.'*
Worst case scenario I'll add another sibling view with the second height and duplicate the UI elements but i want to avoid this.
Edit 1: I get that exception when i've this self.topicHeaderView.translatesAutoresizingMaskIntoConstraints = NO;
If i don't have it, i get this
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. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "", "" )
Will attempt to recover by breaking constraint
Break on objc_exception_throw to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.
Edit: 2 On a 4" screen, it looks fine (The red background covers the entire tableHeaderView as i would expect)
On a 3.5" screen, the red background (which is applied on the nib, extends to a certain height even though i set the height to be 117.0f. The UI elements that are inside the tableHeaderView shows up correctly)
The blue line at the bottom is the separator line and the blue border is around the tableHeaderView.
回答1:
When you are adding a view as a header or footer to the table view, you cannot use constraints on this view, but only inside it. Also the view must be on the top of the hierarchy (as you have), if you move it as a subview to another view, it will give the same error.
You can change view's height directly in code by setting the same frame with changed height. This is working fine.
Also remember that this changes will not apply until you reassign the header:
tableView.tableHeaderView.frame = ...;
tableView.tableHeaderView = tableView.tableHeaderView;
回答2:
I had the same issue, I couldn't use constraints on the tableHeaderView.
Then I created another subView to create the constraints into.
// 1 - create a header view and a subHeaderView
UIView *headerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, bounds.size.width, bounds.size.height - 64.f)];
headerView.backgroundColor = [UIColor blackColor];
tableView.tableHeaderView = headerView;
UIView *subHeaderView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, bounds.size.width, bounds.size.height - 64.f)];
[headerView addSubview:subHeaderView];
// 2 - add constrainedView to subHeaderView (E.g.)
UIView *constrainedView = [UIView new];
[constrainedView setTranslatesAutoresizingMaskIntoConstraints:NO];
[subHeaderView addSubView:constrainedView];
// 3 - addConstraints of subviews into subHeaderView (E.g.)
[subHeaderView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[constrainedView]|" options:0 metrics:metrics views:views]];
[subHeaderView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[constrainedView]|" options:0 metrics:metrics views:views]];
This is working on my project, iOS 7.0 / Xcode 5.0.2
来源：https://stackoverflow.com/questions/18840419/adding-constraint-to-a-uitableview-headerview