Swift asynch load image from directory - ios

Question

I have a situation where I am filling out a form and set image from library then storing in a directory.
I am able to get image from the directory but tableview list flickering in the middle of scroll, so I am working with method of dispatch_async but not able to do.
If anybody has a solution, please let me know.
Here is my code.
import UIKit
func getDocumentsURL() -> NSURL {
let documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
return documentsURL
}
func fileInDocumentsDirectory(filename: String) -> String {
let fileURL = getDocumentsURL().URLByAppendingPathComponent(filename)
return fileURL.path!
}
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource{
var marrEmpData : NSMutableArray!
#IBOutlet var MyTable: UITableView!
#IBAction func addEmpInfo(){
}
override func viewWillAppear(animated: Bool) {
self.getStudentData()
}
func getStudentData()
{
marrEmpData = NSMutableArray()
marrEmpData = ModelManager.getInstance().getAllStudentData()
MyTable.reloadData()
}
override func viewDidLoad() {
super.viewDidLoad()
MyTable.delegate = self
MyTable.dataSource = self
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int{
//return names.count;
return marrEmpData.count;
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell:CustomCell = self.MyTable.dequeueReusableCellWithIdentifier("cells") as! CustomCell
let emp:EmpInfo = marrEmpData.objectAtIndex(indexPath.row) as! EmpInfo
let randomNum = "Image-\(indexPath.row+1).png"
let imagePathOne = fileInDocumentsDirectory(randomNum)
dispatch_async(dispatch_get_main_queue()) {
if let loadedImage = self.loadImageFromPath(imagePathOne) {
print("view Loaded Image: \(loadedImage)")
cell.photo.image = loadedImage
}
else {
cell.photo.image = UIImage(named: "default_user")
}
}
// user profile
cell.name.text = emp.full_name
cell.age.text = emp.age
cell.phone.text = emp.phone
return cell
}
// which one is tapped
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
print("You tapped cell number \(indexPath.row).")
}
// load image of user
func loadImageFromPath(path: String) -> UIImage? {
print("image-----\(path)")
let image = UIImage(contentsOfFile: path)
if image == nil {
print("missing image at: \(path)")
}
print("Loading image from path: \(path)") // this is just for you to see the path in case you want to go to the directory, using Finder.
return image
}
}

Answer 1

You are using dispatch_async but you are dispatching to the main queue which is the thread you are already on. You should dispatch to a background thread, load the image, then dispatch to the main thread and update the UI.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0))
{
let image = self.loadImageFromPath(imagePathOne)
dispatch_async(dispatch_get_main_queue())
{
if let loadedImage = image
{
print("view Loaded Image: \(loadedImage)")
cell.photo.image = loadedImage
}
else
{
cell.photo.image = UIImage(named: "default_user")
}
}
}