Question

我试图学习Swift＆amp;同时iOS dev的基础知识，所以请耐心等待。我有TableViewController首先正在解析本地JSON文件并将其非常简单的数据呈现到TableViewCell和SectionHeaderViews中。在同一个TableViewController内，我正在调用JSON端点，这是返回数据，然后我将其设置为变量，以便我可以访问我实际想要获取的内容（ API结构不太理想）。所以，我最终将正确的数据设置为self.tableData，然后调用self.tableView.reloadData()但没有任何反应。是什么给了什么？

import UIKit

class BusinessTableViewController: UITableViewController {

    var data: NSMutableData = NSMutableData()
    var tableData: NSArray = NSArray()

    @lazy var Business: NSArray = {
        let pathTCT = NSBundle.mainBundle().pathForResource("TCT", ofType: "json")
        let data = NSData.dataWithContentsOfFile(pathTCT, options: nil, error: nil)
        return NSJSONSerialization.JSONObjectWithData(data, options: nil, error: nil) as NSArray
        }()

    override func viewDidLoad() {
        super.viewDidLoad()

        navigationItem.titleView = UIImageView(image: UIImage(named: "growler"))

        tableView.registerClass(BeerTableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.separatorStyle = .None

        fetchKimono()
    }

    override func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
//        return Business.count
        return 1
    }

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        let biz = Business[section] as NSDictionary
        let results = biz["results"] as NSDictionary
        let beers = results["collection1"] as NSArray
        return beers.count
    }

    override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
        let cell = tableView!.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath!) as BeerTableViewCell
        if let path = indexPath {
            let biz = Business[path.section] as NSDictionary
            let results = biz["results"] as NSDictionary
            let beers = results["collection1"] as NSArray
            let beer = beers[path.row] as NSDictionary

            cell.titleLabel.text = beer["BeerName"] as String
        }

        return cell
    }

    override func tableView(tableView: UITableView!, titleForHeaderInSection section: Int) -> String! {
        let biz = Business[section] as NSDictionary
        return biz["name"] as String
    }

    override func tableView(tableView: UITableView!, viewForHeaderInSection section: Int) -> UIView! {
        let biz = Business[section] as NSDictionary
        let view = LocationHeaderView()
        view.titleLabel.text = (biz["name"] as String).uppercaseString
        return view
    }

    override func tableView(tableView: UITableView!, heightForHeaderInSection section: Int) -> CGFloat {
        return 45
    }

    func fetchKimono() {
        var urlPath = "names have been changed to protect the innocent"
        var url: NSURL = NSURL(string: urlPath)
        var request: NSURLRequest = NSURLRequest(URL: url)
        var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: false)

        connection.start()
    }

    func connection(didReceiveResponse: NSURLConnection!, didReceiveResponse response: NSURLResponse!) {
        // Recieved a new request, clear out the data object
        self.data = NSMutableData()
    }

    func connection(connection: NSURLConnection!, didReceiveData data: NSData!) {
        // Append the recieved chunk of data to our data object
        self.data.appendData(data)
    }

    func connectionDidFinishLoading(connection: NSURLConnection!) {
        // Request complete, self.data should now hold the resulting info
        // Convert the retrieved data in to an object through JSON deserialization
        var err: NSError
        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options:    NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        var results: NSDictionary = jsonResult["results"] as NSDictionary
        var collection: NSArray = results["collection1"] as NSArray
        if jsonResult.count>0 && collection.count>0 {
            var results: NSArray = collection as NSArray
            self.tableData = results
            self.tableView.reloadData()
        }
    }
}

Answer 1

您需要通过以下方式在UI主题上重新加载表格。

//swift 2.3
dispatch_async(dispatch_get_main_queue(), { () -> Void in
    self.tableView.reloadData()
})

//swift 3
DispatchQueue.main.async{
    self.tableView.reloadData()
}

跟进： connection.start()方法的一个更简单的替代方法是使用NSURLConnection.sendAsynchronousRequest(...)

//NSOperationQueue.mainQueue() is the main thread
NSURLConnection.sendAsynchronousRequest(NSURLRequest(URL: url), queue: NSOperationQueue.mainQueue()) { (response, data, error) -> Void in
    //check error
    var jsonError: NSError?
    let json: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.allZeros, error: &jsonError)
    //check jsonError
    self.collectionView?.reloadData()
}

这不允许您灵活地跟踪字节，例如，您可能希望通过bytesDownloaded / bytesNeeded计算下载进度

Answer 2

您只需输入：

首先是IBOutlet：

@IBOutlet var appsTableView : UITableView

然后在Action func：

self.appsTableView.reloadData()

Answer 3

如果您的连接是在后台线程中，那么您应该像这样更新主线程中的UI

self.tblMainTable.performSelectorOnMainThread(Selector("reloadData"), withObject: nil, waitUntilDone: true)

As I have mentioned here

斯威夫特4：

self.tblMainTable.performSelector(onMainThread: #selector(UICollectionView.reloadData), with: nil, waitUntilDone: true)

Answer 4

在我的情况下，表格已正确更新，但没有为图像调用setNeedDisplay（），因此我错误地认为数据未重新加载。

Answer 5

所以，问题是我试图不恰当地使用@lazy，这导致我的Business变量基本上是一个常数，因此是不可编辑的。此外，我现在只加载从API返回的数据，而不是加载本地json。

import UIKit

class BusinessTableViewController: UITableViewController {

    var data: NSMutableData = NSMutableData()
    var Business: NSMutableArray = NSMutableArray()

    override func viewDidLoad() {
        super.viewDidLoad()

        navigationItem.titleView = UIImageView(image: UIImage(named: "growler"))

        tableView.registerClass(BeerTableViewCell.self, forCellReuseIdentifier: "cell")
        tableView.separatorStyle = .None

        fetchKimono()
    }

    override func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
        return Business.count
    }

    override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
        if (Business.count > 0) {
            let biz = Business[section] as NSDictionary
            let beers = biz["results"] as NSArray
            return beers.count
        } else {
            return 0;
        }
    }

    override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
        let cell = tableView!.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath!) as BeerTableViewCell
        if let path = indexPath {
            let biz = Business[path.section] as NSDictionary
            let beers = biz["results"] as NSArray
            let beer = beers[path.row] as NSDictionary

            cell.titleLabel.text = beer["BeerName"] as String
        } else {
            cell.titleLabel.text = "Loading"
        }

        return cell
    }

    override func tableView(tableView: UITableView!, viewForHeaderInSection section: Int) -> UIView! {
        let view = LocationHeaderView()
        let biz = Business[section] as NSDictionary
        if (Business.count > 0) {
            let count = "\(Business.count)"
            view.titleLabel.text = (biz["name"] as String).uppercaseString
        }
        return view
    }

    override func tableView(tableView: UITableView!, heightForHeaderInSection section: Int) -> CGFloat {
        return 45
    }

    func fetchKimono() {
        var urlPath = "names have been removed to protect the innocent"
        var url: NSURL = NSURL(string: urlPath)
        var request: NSURLRequest = NSURLRequest(URL: url)
        var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: false)

        connection.start()
    }

    func connection(didReceiveResponse: NSURLConnection!, didReceiveResponse response: NSURLResponse!) {
        // Recieved a new request, clear out the data object
        self.data = NSMutableData()
    }

    func connection(connection: NSURLConnection!, didReceiveData data: NSData!) {
        // Append the recieved chunk of data to our data object
        self.data.appendData(data)
    }

    func connectionDidFinishLoading(connection: NSURLConnection!) {
        // Request complete, self.data should now hold the resulting info
        // Convert the retrieved data in to an object through JSON deserialization
        var err: NSError
        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        var results: NSDictionary = jsonResult["results"] as NSDictionary
        var collection: NSArray = results["collection1"] as NSArray
        if jsonResult.count>0 && collection.count>0 {
            Business = jsonResult
            tableView.reloadData()
        }
    }
}

Swift Docs on @lazy：

必须始终将lazy属性声明为变量（使用var关键字），因为在实例初始化完成之后才可能检索其初始值。常量属性在初始化完成之前必须始终具有值，因此不能声明为惰性。

Answer 6

除了来自UI /主线程的明显reloadData（无论Apple称之为什么），在我的情况下，我忘记了也更新了SECTIONS信息。因此它没有检测到任何新的部分！

Answer 7

对UI的所有调用都应该是异步的，在UI上更改的任何内容（如更新表或更改文本标签）都应该从主线程完成。使用DispatchQueue.main会将您的操作添加到主线程上的队列中。

Swift 4

DispatchQueue.main.async{
    self.tableView.reloadData()
}

Answer 8

您必须仅在主线程中重新加载TableView。。否则，您的应用将崩溃或一段时间后将被更新。对于每个UI更新，建议使用主线程。

//To update UI only this below code is enough
//If you want to do changes in UI use this
DispatchQueue.main.async(execute: {
    //Update UI
    self.tableView.reloadData()//Your tableView here
})

//Perform some task and update UI immediately.
DispatchQueue.global(qos: .userInitiated).async {  
    // Call your function here
    DispatchQueue.main.async {  
        // Update UI
        self.tableView.reloadData()  
    }
}

//To call or execute function after some time and update UI
DispatchQueue.main.asyncAfter(deadline: .now() + 5.0) {
    //Here call your function
    //If you want to do changes in UI use this
    DispatchQueue.main.async(execute: {
        //Update UI
        self.tableView.reloadData()
    })
}

Answer 9

尝试一下：tableView.reloadSections（IndexSet（integersIn：0 ... 0），带有：.automatic）它对我有帮助

Answer 10

我也面临着同样的问题，我做错了是我忘记添加

tableView.delegate = self    
tableView.dataSource = self

在viewDidLoad（）{}方法中。这可能是self.tableView.reloadData（）无法正常工作的原因之一。

self.tableView.reloadData（）在Swift中不起作用

10 个答案: