在TableView中使用parse.com图像时出错

Question

I am running this code for creating a tableview based on a parse query. It works, problem is I get the following error:

2014-09-24 01:09:32.187 inventario[253:20065] Warning: A long-running Parse operation is being executed on the main thread. Break on warnParseOperationOnMainThread() to debug.

I get this when using " var datta = image?.getData() " for getting the image in place. Any ideas?

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

            let sweet:PFObject = self.timelineData.objectAtIndex(indexPath.row) as PFObject

            cell.textLabel?.text = sweet.objectForKey("Modelo") as? String
            cell.detailTextLabel?.text = sweet.objectForKey("Marca") as? String

            // This part is the problem
            var image = sweet.objectForKey("Foto3") as? PFFile
            var datta = image?.getData()
            cell.imageView?.image = UIImage(data: datta!)

            cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator

            return cell
        }

The method for the query was:

{ @IBAction func loadData(){

        var findTimelineData:PFQuery = PFQuery(className: "InventarioListado")
        findTimelineData.whereKey("Categoria", equalTo: toPassInventario)
        findTimelineData.whereKey("Descripcion", equalTo: toPassModeloEquipoInventario)
        //findTimelineData.orderByAscending("Descripcion")
        findTimelineData.limit = 500

        findTimelineData.findObjectsInBackgroundWithBlock{
            (objects:[AnyObject]!, error:NSError!)->Void in

            if error == nil{
                for object in objects{
                    let sweet:PFObject = object as PFObject

                    let sweeter:NSString! = sweet.objectForKey("Modelo") as? NSString
                    var filtro = self.categoriasFiltradasDeInventario.containsObject(sweeter!)
                    if (filtro == false) {
                        self.categoriasFiltradasDeInventario.addObject(sweeter)
                        self.timelineData.addObject(sweet)
                    }
                    self.tableView.reloadData()

                }
            }

        }
    }

}

Answer 1

The problem is that the getData() function loads data via network connection and it can take some time to download an image. Your main thread would be blocked during this time so it's highly recommended to run it in the background. You can use getDataInBackgroundWithBlock() to do that easily.

let image = sweet["Foto3"] as PFFile
image.getDataInBackgroundWithBlock {
    (imageData: NSData!, error: NSError!) -> Void in
    if error == nil {
       cell.imageView?.image = UIImage(data:imageData)
    }
}

Answer 2

• There is a basic concept in programming, Run the UI code on UI thread and Non-UI code in Non-UI thread.

• Running the CPU intensive code like Network calls, I/O calls etc should be on Non-UIthread/Background thread.

• Parse query to fetch image is a network call that is to be made on a background thread so the UI don't get strucked .

• Use shared NSOperationQueue to shoot the query.