CODEWITHSUNDEEP
iosswiftanimationdispatch-async
kuzdu
kuzdu

Reputation: 7524

Swift: dispatch_async is effect is inconsistent for animation

I have a globalstate in my app. Depending on the state the GUI is different.

When I go from the start View A to View B I have globalstate 3 It should show an information screen, but it doesn't. BUT: When the View B has loaded only once and I jump from View C/D/E back to View B, then the code work perfectly. (You have to be in View A to get in View B.)

I use a lot dispatch_async(dispatch_get_main_queue.. that isn't good style, is it?

Why is my animation not loading at the beginning? What is good style? Thank you for answers and sorry for mistakes (english isn't my mothertongue)

  override func viewDidLoad() {
    super.viewDidLoad()

    dispatch_async(dispatch_get_main_queue(), {

        self.animateTheInformationViewWhenGlobalStateIsThree()
    })

  }


func animateTheInformationViewWhenGlobalStateIsThree() {

    print("GLOGBALSTATE \(globalState)") //it is 3


    if globalState == 3 {

        setGlobalState(3)

        dispatch_async(dispatch_get_main_queue(), {
            GUITools.animateTheInformationView(self.tableView, animateBottomLayout: self.animationBottomConstraint, value: self.negativValue)
        })

        print("THE POSITIV VALUE THE NEGATIV")
    }

//GUITools-Static-Class: 

class func animateTheInformationView(tableView: UITableView, animateBottomLayout: NSLayoutConstraint, value: CGFloat) {


    dispatch_async(dispatch_get_main_queue(), {

    animateBottomLayout.constant += value


        UIView.animateWithDuration(Constants.animationTime, animations: { () -> Void in

            tableView.layoutIfNeeded()

            },completion: {
                (value: Bool) in
        })

    })

}

EDIT With viewDidAppear it works. But the animation isn't a real animation. The tableView "jumps". So there is no sliding/animation.

I deleted all dispatch_async..

override func viewDidAppear(animated: Bool) { self.animateTheInformationViewWhenGlobalStateIsSeven() }

Upvotes: 0

Views: 630

Answers (1)

fluidsonic
fluidsonic

Reputation: 4676

viewDidLoad() does not mean that your view is already visible. Since it's not visible yet you cannot apply animations to it. viewDidLoad() is only meant to configure your view controller's view and set up your view hierarchy - i.e. to add subviews.

What you want to use is viewWillAppear() (or viewDidAppear()) to start your animation as soon as the view becomes (or became) visible.

Also all the dispatch_async calls are most likely unnecessary. You usually only need them when you are not on the main (= UI) thread. Simply remove them.

Upvotes: 2

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