自动布局不起作用？

Question

我在使用自动布局设置的表格视图顶部有一个搜索栏，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)]];

当我运行它时，一切看起来都很好。但是当我在开始编辑搜索栏之前执行_searchBar.showsScopeBar = YES; 时，搜索栏和表格视图不会自动调整大小。即使我这样做[_searchBar sizeToFit]，表格视图也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视图的标题；它只是一个父视图和两个子视图。 注2：我在调用_searchBar.showsScopeBar = YES;之前和之后检查了_searchBar的intrinsicContentSize，大小确实发生了变化。

Answer 1

你必须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];
}

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