Question

当用户向下滚动到页面的某个百分比时，我会回发到我的数据库以获取更多数据。但是，当用数据更新子视图时，我注意到滚动中有轻微的冻结。因为所有的调用都是异步的，所以我不确定我做错了什么

func PostBackAsync(PassURL:String, username:String, completion: (jsonData: NSDictionary?, error: NSError?)->Void) {

    let post:NSString = "username=\(username)";
    let url:NSURL = NSURL(string:PassURL)!
    let postData = post.dataUsingEncoding(NSUTF8StringEncoding)!

    let postLength = String(postData.length)
    //Setting up `request` is similar to using NSURLConnection
    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = "POST"
    request.HTTPBody = postData
    request.setValue(postLength, forHTTPHeaderField: "Content-Length")
    request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
    request.setValue("application/json", forHTTPHeaderField: "Accept")


    let session = NSURLSession.sharedSession()
    let task = session.dataTaskWithRequest(request) {urlData, response, reponseError in

        if let receivedData = urlData {
            let res = response as! NSHTTPURLResponse!;

            NSLog("Response code: %ld", res.statusCode);

            if (res.statusCode >= 200 && res.statusCode < 300) {
                do {
                    let jsonData = try NSJSONSerialization.JSONObjectWithData(receivedData, options: []) as! NSDictionary
                    //On success, invoke `completion` with passing jsonData.
                    completion(jsonData: jsonData, error: nil)
                } catch {
                    //On error, invoke `completion` with NSError.
                    completion(jsonData: nil, error: nil)
                }                      }
            else
            {
                completion(jsonData: nil, error: nil)
            }
        }
    }
    task.resume()
} 

 func PostBack(PassURL:String, username:String) {
    PostBackAsync(PassURL, username: username) {jsonData, error in
        if let json = jsonData {

            dispatch_async(dispatch_get_main_queue(), {

                let success:NSInteger = json.valueForKey("success") as! NSInteger

                if(success == 1)
                {
                   for var index=0; index < myArray.count; index++
                    {

                    //Do some Data Manipulation...
                    //..............
                     self.newView.addSubview(a[index] as! String)       
                     self.newView.addSubview(b[index] as! String)
                  self.myScrollView.contentSize = CGSize(width: aWidth, height: myscrollViewContentSize)
                  //newView is the main subview inside of the scrollview
                  self.newView.frame = CGRectMake(0, 0, self.myScrollView.frame.width, myscrollViewContentSize)
}
}
}) }}

在更新此信息时，为什么UIScrollview滚动会稍微冻结，有什么突出的地方？

Answer 1

您可能需要定义要运行异步操作的线程，以确保它不在UI线程上运行。请参阅此答案：https://stackoverflow.com/a/16283719/2347118

在UIScrollview中更新子视图时滚动期间轻微冻结

1 个答案: