UISearchController: show results even when search

问题:

As I understand, the default behaviour of UISearchController is:

1. On tapping search bar, background is dimmed and 'cancel' button is shown. SearchResultsController is not shown till this point.
2. SearchResultsController is displayed only if search bar is not empty.

I want to display SearchResultsController even when search bar is empty but selected (i.e is case 1 above).

Simply put, instead of background dimming, I would like to show Search results.

Is there a way for doing this?

More Clarification:

I am not using UISearchController to filter results shown on the view on which it is shown, but some other unrelated results. It will be like what facebook does on its 'News Feed'. Tapping on search bar shows search suggestions initially and then, when we start editing, it shows search results which might not be related to news feed.

回答1:

If your searchBar is active but has no text, the underlying tableView results are shown. That's the built-in behavior, and the reason why searchResultsController is hidden for that state.

To change the behavior when search is active but not filtering, you're going to have to show the searchResultsController when it is normally still hidden.

There may be a good way to accomplish this via <UISearchResultsUpdating> and updateSearchResultsForSearchController:. If you can solve it via the protocol, that's the preferred way to go.

If that doesn't help, you're left with hacking the built-in behavior. I wouldn't recommend or rely on it, and it's going to be fragile, but here's an answer if you choose that option:

1. Make sure your tableViewController conforms to <UISearchControllerDelegate>, and add

   self.searchController.delegate = self;

2. Implement willPresentSearchController:

   - (void)willPresentSearchController:(UISearchController *)searchController
   {
       dispatch_async(dispatch_get_main_queue(), ^{
           searchController.searchResultsController.view.hidden = NO;
       });
   }
   

   This makes the searchResultsController visible after its UISearchController set it to hidden.

3. Implement didPresentSearchController:

   - (void)didPresentSearchController:(UISearchController *)searchController
   {
       searchController.searchResultsController.view.hidden = NO;
   }
   

For a better way to work around the built-in behavior, see malhal's answer.

回答2:

You can simply implement the UISearchResultsUpdating protocol and set the results controller view to always show in updateSearchResultsForSearchController:

 func updateSearchResultsForSearchController(searchController: UISearchController) {

   // Always show the search result controller
   searchController.searchResultsController?.view.hidden = false

   // Update your search results data and reload data
   ..
}

This works because the method is called even when the search bar is activated, without any text.

回答3:

I have tried PetahChristian solution, the preload result did show up when we first focus the searchbar, but when we enter something then clear it, the preload results will not reappear.

I came up with another solution. We only need to add a delegate into SearchResultsController and call it when our searchController.searchBar.text is empty. Something like this:

SearchResultsController:

protocol SearchResultsViewControllerDelegate {
   func reassureShowingList() -> Void
}

class FullSearchResultsViewController: UIViewController, UISearchResultsUpdating{
   var delegate: SearchResultsViewControllerDelegate?
   ...
   func updateSearchResultsForSearchController(searchController: UISearchController) {
    let query = searchController.searchBar.text?.trim()
    if query == nil || query!.isEmpty {
        ...
        self.delegate?.reassureShowingList()
        ...
    }
    ...
}

And in the controller contains the SearchController, we add our delegate:

self.searchResultsController.delegate = self
func reassureShowingList() {
    searchController.searchResultsController!.view.hidden = false
}

回答4:

With tricky things like this I recommend the sledge hammer approach! That is to detect when something tries to make it hidden and when it does, change it back. This can be done via KVO (Key Value Observing). This will work no matter what, without having to handle all the intricacies of the search bar. Sorry the code is complicated but KVO is an older style API but my code follows recommend practice. In your SearchResultsViewController put this:

static int kHidden;

@implementation SearchResultsViewController

-(void)viewDidLoad{
    [super viewDidLoad];
    [self.view addObserver:self
                   forKeyPath:@"hidden"
                      options:(NSKeyValueObservingOptionNew |
                               NSKeyValueObservingOptionOld)
                      context:&kHidden];
}

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {
    // if it was our observation
    if(context == &kHidden){
        // if the view is hidden then make it visible.
        if([[change objectForKey:NSKeyValueChangeNewKey] boolValue]){
            self.view.hidden = NO;
        }
    }
    else{
        // if necessary, pass the method up the subclass hierarchy.
        if([super respondsToSelector:@selector(observeValueForKeyPath:ofObject:change:context:)]){
            [super observeValueForKeyPath:keyPath
                                 ofObject:object
                                   change:change
                                  context:context];
        }
    }
}

- (void)dealloc
{
    [self.view removeObserver:self forKeyPath:@"hidden"];
}

// Here have the rest of your code for the search results table.

@end

This works in all cases including if the text is cleared.

Lastly, to prevent the table doing an ugly fade to grey then to white when the search activates, use this:

self.searchController.dimsBackgroundDuringPresentation = NO;

回答5:

Swift 3 Version:

If your searchResultController is not nil and you are using a separate table view controller to show the search results, then you can make that table view controller conform to UISearchResultUpdating and in the updateSearchResults function, you can simply unhide the view.

func updateSearchResults(for searchController: UISearchController) {
    view.hidden = false
}

Swift 4 Version:

func updateSearchResults(for searchController: UISearchController) {
    view.isHidden = false
}

回答6:

The Swift 2.3 version of @malhal's approach:

class SearchResultsViewController : UIViewController {
    var context = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        // Add observer
        view.addObserver(self, forKeyPath: "hidden", options: [ .New, .Old ], context: &context)
    }

    deinit {
        view.removeObserver(self, forKeyPath: "hidden")
    }

    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        if context == &self.context {
            if change?[NSKeyValueChangeNewKey] as? Bool == true {
                view.hidden = false
            }
        } else {
            super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
        }
    }
}

回答7:

What is being hidden is the search results controller's view. Therefore it is sufficient to unhide it any time it might be hidden. Simply do as follows in the search results controller:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.view.isHidden = false
}

func updateSearchResults(for searchController: UISearchController) {
    self.view.isHidden = false
    // ... your other code goes here ...
}

Now the results view (i.e. the table view) is always visible, even when the search bar text is empty.

By the way, the iOS Mail app behaves like this, and I assume that's how it's implemented (unless Apple has access to some secret private UISearchController setting).

[Tested in iOS 10 and iOS 11; I didn't test on any earlier system.]

回答8:

I am recently working on UISearchController. I want to show search history in searchResultsController when search bar is empty. So searchResultsController needs to show up when UISearchController is presented.

I am not quite satisfied with the solutions which flip the hidden flag set by UISearchController (built-in behaviour). I have tried another solution to make the searchResultsController always visible by overriding the hidden property in a custom view.

for example, my searchResultsController is a UITableViewController. I create a VisibleTableView as a subclass of UITableView, and then change the UITableView custom class of searchResultsController to VisibleTableView in xib or storyboard. This way, my searchResultsController will never be hidden by UISearchController.

The good things here:

1. Easier to implement than KVO.

2. No delay to show searchResultsController. Flipping the hidden flag in "updateSearchResults" delegate method works, but there is a delay to show the searchResultsController.

3. It does't reset the hidden flag, so there is no UI gap/jumping between hidden and visible.

Swift 3 sample code:

class VisibleTableView: UITableView {
override var isHidden: Bool {
    get {
        return false
    }
    set {
        // ignoring any settings
    }
}
}

回答9:

I think you are mistaken.

SearchResultsController only appears when there are results. This is slightly different than your interpretation.

The results are loaded manually based on the text in the search bar. So you can intercept it if the search bar is empty and return your own set of results.

回答10:

If you don't want to dim the results, set the dimsBackgroundDuringPresentation property to false.

This will make sure that the underlying content is not dimmed during a search.

You will also have to make sure you return results even when the searchText is empty otherwise an empty tableview will be displayed.

回答11:

I spent a lot of time with this, and ultimately the solution I went with is like @malhals's, but the amount of code is significantly reduced by using facebook's KVOController: https://github.com/facebook/KVOController . Another advantage here is that if your searchResultsController is a UINavigationController then you don't need to subclass it just to add @malhal's code.

// always show searchResultsController, even if text is empty
[self.KVOController observe:self.searchController.searchResultsController.view keyPath:@"hidden" options:NSKeyValueObservingOptionNew block:^(id observer, UIView* view, NSDictionary *change) {
    if ([change[NSKeyValueChangeNewKey] boolValue] == YES) {
        view.hidden = NO;
    }
}];
self.searchController.dimsBackgroundDuringPresentation = NO;

回答12:

The easiest way is to use ReactiveCocoa with this extension https://github.com/ColinEberhardt/ReactiveTwitterSearch/blob/master/ReactiveTwitterSearch/Util/UIKitExtensions.swift

        presentViewController(sc, animated: true, completion: {
            sc.searchResultsController?.view.rac_hidden.modify({ value -> Bool in
                return false
            })
        } )

where sc is your UISearchController

回答13:

I really liked Simon Wang's answer and worked with it and this is what I did and it works perfectly:

I subclass the UISearchController in my custom class:

class CustomClass: UISearchController {
  override var searchResultsController: UIViewController? {
    get {
      let viewController = super.searchResultsController
      viewController?.view.isHidden = false
      return viewController
    }
    set {
      // nothing
    }
  }
}

Also make sure you don't have this anywhere in your code:

self.resultsSearchController.isActive = true

resultsSearchController is my UISearchController

回答14:

Swift 4 version of malhals answer:

class SearchController: UISearchController {

    private var viewIsHiddenObserver: NSKeyValueObservation?

    override func viewDidLoad() {
        super.viewDidLoad()

        viewIsHiddenObserver = self.searchResultsController?.view.observe(\.hidden, changeHandler: { [weak self] (view, _) in
            guard let searchController = self else {return}
            if view.isHidden && searchController.searchBar.isFirstResponder {
            view.isHidden = false
            }
        })

    }

}

Please note the [weak self]. Otherwise you would introduce a retain cycle.