iOS - UISearchBar 动态搜索结果在快速输入时不起作用(快速)

Question

我想要的是一个搜索栏，当用户在搜索栏中输入每个字符时，它会使用用户名更新表格 View 。当用户删除(退格)搜索栏中的所有字符时，即搜索栏为空，我希望表格 View 不显示用户名并且为空。

我有一个半功能的 UISearchbar，可以搜索用户名(解析后端)。当我在搜索栏中缓慢地逐个字符输入时，它工作得很好。

但是，当我快速输入时，搜索结果有点偏离 - 它显示了之前输入的字符中的用户名。例如:如果我快速输入“nik”，它仍然会显示带有“ni”的用户名。另外，当我快速退格直到搜索栏中没有字符时，它仍然会显示某些用户名。

同样，当我缓慢输入字符时，它工作得很好，但我觉得它不是很有效。我尝试了各种各样的方法，但到目前为止没有任何效果。我已在下面添加了相关代码，如果您需要更多信息，请告诉我。

    // called when keyboard search button pressed
func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {

    let searchString = searchBar.text;

    if (searchString != "") {
        //do load users
        loadUsers(searchText: searchString!);
        print("called from searchBarSearchButtonClicked");
    }

}

// called when cancel button pressed
func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {

    searchBar.text = "";

    //hide tableview maybe?!
    //searchTableView.isHidden = true;

}

func updateSearchResults(for searchController: UISearchController) {
    let searchString: String = (searchController.searchBar.text)!;


    /*if (searchString == "" && !searchActive) {
        searchResults.removeAll(keepingCapacity: false);
        searchTableView.reloadData();
        print("test");
    }*/

    if (searchString != "" && !self.searchActive) {
        loadUsers(searchText: searchString);
        print("called from updateResults");
    }

    if (searchString == "") {
        searchResults.removeAll(keepingCapacity: false);
        searchTableView.reloadData();
        print("test");
    }
}


func loadUsers(searchText: String ) {

    if(searchText != "") {


        let usernameQuery = PFUser.query();
        //usernameQuery?.whereKey("username", equalTo: searchText);
        usernameQuery?.whereKey("username", contains: searchText.lowercased());


        let fbUsername = PFUser.query();
        fbUsername?.whereKey("username", contains: searchText);


        let firstnameQuery = PFUser.query();
        //firstnameQuery?.whereKey("last_name", equalTo: searchText)
        firstnameQuery?.whereKey("last_name", contains: searchText);


        let lastnameQuery = PFUser.query();
        //lastnameQuery?.whereKey("first_name", equalTo: searchText);
        lastnameQuery?.whereKey("first_name", contains: searchText);


        let query = PFQuery.orQuery(withSubqueries: [usernameQuery!,fbUsername!, firstnameQuery!, lastnameQuery!]);

        searchActive = true;

        query.findObjectsInBackground { (objects, error) in

            if error != nil {

                print("There was an error getting userlist");

            }

            else {

                if let object = objects {

                    self.searchResults.removeAll(keepingCapacity: false);

                    for object in objects! {

                        let user = object.object(forKey: "username") as! String;
                        self.searchResults.append(user);

                    }

                    //self.searchTableView.reloadData();


                    DispatchQueue.main.async {

                     self.searchTableView.reloadData();

                     //self.userSearchController.searchBar.resignFirstResponder();

                     }

                }

            }

            self.searchActive = false;

        }
    }

}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if(userSearchController.isActive) {

        print(searchResults.count);
        return searchResults.count;

    }

    return 0;
}


public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath);

    if(self.userSearchController.isActive && searchResults.count > indexPath.row) {

        print(searchResults[indexPath.row]);
        cell.textLabel?.text = searchResults[indexPath.row];

    }

    return cell;

}




/*
public func searchBarShouldBeginEditing(_ searchBar: UISearchBar) -> Bool {
    return true;
}

public func searchBarShouldEndEditing(_ searchBar: UISearchBar) -> Bool {
    return true;
}



func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {

        //loadUsers(searchText: (searchBar.text)!);
} */


func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {

    if (searchBar.text != "" ) {
        NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(loadUsers(searchText:)), object: searchBar.text! as String);


        perform(#selector(loadUsers(searchText:)), with: searchBar.text! as String, afterDelay: 0.50);


        print("called from textDidChange");

    }
    if (searchBar.text == "") {

        searchResults.removeAll(keepingCapacity: false);
        searchTableView.reloadData();
        print("test2");
    }

}

Answer 1

我通过使用计时器解决了这个问题。下面的代码在调用您的函数之前等待一秒钟。如果在那一秒内发生文本更改，它将使先前安排的计时器无效，并且只执行第二个计时器。您可以通过在函数中打印搜索文本来检查这一点。

var timer: Timer?

func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
        timer?.invalidate() //cancels out previous Timers
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(myFunctionThatDoesServerSearch), userInfo: nil, repeats: false)  
    }