UISearchBar 忽略编程约束

Question

我正在尝试构建一个 ViewController 子类，它利用 UISearchController 来显示结果。该视图有一个输入字段，我想将其动画化到屏幕顶部，以便用户有最大的空间来查看结果。

我使用 UIView 构建了一个概念证明，该 UIView 包装了一个搜索栏下拉组件，并在 Storyboard 中将它们的顶部、前导、尾随和底部约束设置为相等。以下代码负责为不同的动作设置动画：

- (void)keyboardWillAppear:(NSNotification*)notification {
    self.labelToSearchBarSpaceConstraint.active = NO;
    self.searchBarAtTopConstraint.active = YES;
    self.searchBarLeadingSpaceConstraint.constant = 0;
    self.searchBarTrailingSpaceConstraint.constant = 0;

    [UIView animateWithDuration:[notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue] animations:^{
        [self.view setNeedsLayout];
        [self.view layoutIfNeeded];
    }];
}

- (void)keyboardWillDisappear:(NSNotification*)notification {
    self.searchBarAtTopConstraint.active = NO;
    self.labelToSearchBarSpaceConstraint.active = YES;
    self.searchBarLeadingSpaceConstraint.constant = 20;
    self.searchBarTrailingSpaceConstraint.constant = 20;

    [UIView animateWithDuration: [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue] animations:^{
        [self.view setNeedsLayout];
        [self.view layoutIfNeeded];
    }];
}

然后我尝试切换到以编程方式创建的 UISearchController 和 UISearchBar。下面的代码建立了我认为是代码而不是 Storyboard 中的等价关系：

self.definesPresentationContext = YES;

self.searchController = [[UISearchController alloc] initWithSearchResultsController:nil];
UISearchBar* searchBar = self.searchController.searchBar;
searchBar.translatesAutoresizingMaskIntoConstraints = NO;
[self.searchBarView addSubview:searchBar];

[NSLayoutConstraint constraintWithItem:searchBar attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.searchBarView attribute:NSLayoutAttributeTop multiplier:1.0 constant:0.0].active = YES;
[NSLayoutConstraint constraintWithItem:searchBar attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.searchBarView attribute:NSLayoutAttributeLeading multiplier:1.0 constant:0.0].active = YES;
[NSLayoutConstraint constraintWithItem:searchBar attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:self.searchBarView attribute:NSLayoutAttributeTrailing multiplier:1.0 constant:0.0].active = YES;
[NSLayoutConstraint constraintWithItem:searchBar attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self.searchBarView attribute:NSLayoutAttributeBottom multiplier:1.0 constant:0.0].active = YES;

然而，当以这种方式完成时，UISearchBar 对象不遵守约束。当容器向上动画时，搜索栏会飞出页面。为什么会这样？

次要更新：我在 NSLayoutConstraint 的文档中注意到将其活动属性设置为 YES 而不是显式添加它，但行为完全相同。更新代码以匹配。

Answer 1

我在将 UISearchController 的搜索栏添加到 UITableView header 视图时遇到了类似的问题。

在用户选择 searchBar 后，当包含 UITableView 的 containerView 的动画约束时，它不会跟随 containerView。

在我的例子中，在委托 didPresentSearchController:(UISearchController *)searchController 被调用后，searchBar 有一个 UISearchBarContainerView 的超级视图而不是 UITableView header 看法。

Re-adding 它回到了动画帮助我之前的原始 header 视图。

-(void)didPresentSearchController:(UISearchController *)searchController {

    NSLog(@"did present search controller");

    self.tableView.tableHeaderView = self.searchController.searchBar;

    ...animation...

}

UISearchBar 忽略编程约束

UISearchBar ignores programmatic constraints

objective-c

ios

nslayoutconstraint

ios-autolayout

uisearchcontroller