Question

按下时如何添加带活动指示符的刷新栏按钮

这是代码

我使用json从服务器提取数据我希望用户在按下刷新按钮时看到更新的内容

由于

import UIKit
import CoreData


class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    var json_data_url = "http://example/json_table_view_images%20(1).json"
    var image_base_url = ""


    var TableData:Array< datastruct > = Array < datastruct >()

    enum ErrorHandler:ErrorType
    {
        case ErrorFetchingResults
    }


    struct datastruct
    {
        var imageurl:String?
        var description:String?
        var image:UIImage? = nil

        init(add: NSDictionary)
        {
            imageurl = add["url"] as? String
            description = add["description"] as? String
        }
    }

    @IBOutlet var tableview: UITableView!

    override func viewDidLoad() {
        super.viewDidLoad()

        tableview.dataSource = self
        tableview.delegate = self

        get_data_from_url(json_data_url)
    }


    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
    {
        let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath)

        let data = TableData[indexPath.row]


        cell.textLabel?.text = data.description

        if (data.image == nil)
        {
            cell.imageView?.image = UIImage(named:"image.jpg")
            load_image(image_base_url + data.imageurl!, imageview: cell.imageView!, index: indexPath.row)
        }
        else
        {
            cell.imageView?.image = TableData[indexPath.row].image
        }

        return cell

    }

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
    {
        return TableData.count
    }







    func get_data_from_url(url:String)
    {


        let url:NSURL = NSURL(string: url)!
        let session = NSURLSession.sharedSession()

        let request = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "GET"
        request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData


        let task = session.dataTaskWithRequest(request) {
            (
            let data, let response, let error) in

            guard let _:NSData = data, let _:NSURLResponse = response  where error == nil else {
                print("error")
                return
            }

            dispatch_async(dispatch_get_main_queue(), {
                self.extract_json(data!)
                return
            })

        }

        task.resume()

    }


    func extract_json(jsonData:NSData)
    {
        let json: AnyObject?
        do {
            json = try NSJSONSerialization.JSONObjectWithData(jsonData, options: [])
        } catch {
            json = nil
            return
        }

            if let list = json as? NSArray
            {
                for (var i = 0; i < list.count ; i++ )
                {
                    if let data_block = list[i] as? NSDictionary
                    {

                        TableData.append(datastruct(add: data_block))
                    }
                }

                do
                {
                    try read()
                }
                catch
                {
                }

                do_table_refresh()

            }


    }




    func do_table_refresh()
    {
        dispatch_async(dispatch_get_main_queue(), {
            self.tableview.reloadData()
            return
        })
    }


    func load_image(urlString:String, imageview:UIImageView, index:NSInteger)
    {

        let url:NSURL = NSURL(string: urlString)!
        let session = NSURLSession.sharedSession()

        let task = session.downloadTaskWithURL(url) {
            (
            let location, let response, let error) in

            guard let _:NSURL = location, let _:NSURLResponse = response  where error == nil else {
                print("error")
                return
            }

            let imageData = NSData(contentsOfURL: location!)

            dispatch_async(dispatch_get_main_queue(), {


                self.TableData[index].image = UIImage(data: imageData!)
                self.save(index,image: self.TableData[index].image!)

                imageview.image = self.TableData[index].image
                return
            })


        }

        task.resume()


    }




    func read() throws
    {

        do
        {
            let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
            let managedContext = appDelegate.managedObjectContext!
            let fetchRequest = NSFetchRequest(entityName: "Images")

            let fetchedResults = try managedContext.executeFetchRequest(fetchRequest)

            for (var i=0; i < fetchedResults.count; i++)
            {
                let single_result = fetchedResults[i]
                let index = single_result.valueForKey("index") as! NSInteger
                let img: NSData? = single_result.valueForKey("image") as? NSData

                TableData[index].image = UIImage(data: img!)

            }

        }
        catch
        {
            print("error")
            throw ErrorHandler.ErrorFetchingResults
        }

    }

    func save(id:Int,image:UIImage)
    {
        let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        let managedContext = appDelegate.managedObjectContext!

        let entity = NSEntityDescription.entityForName("Images",
            inManagedObjectContext: managedContext)
        let options = NSManagedObject(entity: entity!,
            insertIntoManagedObjectContext:managedContext)

        let newImageData = UIImageJPEGRepresentation(image,1)

        options.setValue(id, forKey: "index")
        options.setValue(newImageData, forKey: "image")

        do {
            try managedContext.save()
        } catch
        {
            print("error")
        }

    }


}

Answer 1

看，你必须在按钮动作中做两件事，你必须调用函数'get_data_from_url()'，然后你必须重新加载tableview。您可以使用tableview.reloadData()重新加载表格视图。

执行此操作后，您可以看到更新的内容。

Answer 2

如果您想要导航栏中的activity indicator，

目标-C

    UIActivityIndicatorView * v= [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[v startAnimating];
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:v];

夫特，

   var myActivityIndicator = UIActivityIndicatorView(activityIndicatorStyle:UIActivityIndicatorViewStyle.Gray)
    myActivityIndicator.center = view.center
    myActivityIndicator.startAnimating()
    var barButtonItem = UIBarButtonItem(customView: view)
    self.navigationItem.rightBarButtonItem = barButtonItem

现在点击＆＃39;刷新＆＃39;按钮使用上面的代码在导航栏上显示活动指示器。

使用上面的代码示例swift类。

import Foundation

导入UIKit

类ViewController：UIViewController {

func addRefreshHeader() {
    let myActivityIndicator = UIActivityIndicatorView(activityIndicatorStyle:UIActivityIndicatorViewStyle.Gray)
    myActivityIndicator.startAnimating()
    let barButtonItem = UIBarButtonItem(customView: myActivityIndicator)
    self.navigationItem.leftBarButtonItem = barButtonItem
} 
}

将带有活动指示符的刷新按钮添加到JSON表视图

2 个答案: