ios - 自动布局不起作用？

Question

我在使用自动布局设置的表格 View 顶部有一个搜索栏，如下所示:

_searchBar.translatesAutoresizingMaskIntoConstraints = NO;
_tableView.translatesAutoresizingMaskIntoConstraints = NO;

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[_searchBar]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_searchBar)]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[_tableView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_tableView)]];

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_searchBar][_tableView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_searchBar, _tableView)]];

运行时一切看起来都不错。但是当我做 _searchBar.showsScopeBar = YES;在我开始编辑搜索栏之前，搜索栏和表格 View 不会自动调整大小。即使我做 [_searchBar sizeToFit] ，表格 View 不会调整大小并向下移动。为什么？？

注意:我没有将搜索栏作为表格 View 的标题；它只是一个父 View 和两个 subview 。注 2:我检查了 intrinsicContentSize的 _searchBar在我打电话之前和之后 _searchBar.showsScopeBar = YES;并且大小确实发生了变化。

Answer 1

您必须invalidateIntrinsicContentSize:

- (void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar
{
    searchBar.showsScopeBar = YES;
    [searchBar invalidateIntrinsicContentSize];
    [searchBar setShowsCancelButton:YES animated:YES];
}

- (void)searchBarTextDidEndEditing:(UISearchBar *)searchBar
{
    searchBar.showsScopeBar = NO;
    [searchBar invalidateIntrinsicContentSize];
    [searchBar setShowsCancelButton:NO animated:YES];
}

参见 UISearchBar's scope button won't show up iOS6