iOS Swift按钮显示延迟

Question

Please consider the following code:

override func viewDidLoad() {
    super.viewDidLoad()

    let images = [
        "Add To Inventory","Move To Display Room","Move To Store Room","Move To Storage","Scrap Inventory"
    ]

    var buttons:[UIButton] = []
    // For use in foreground
    let name=defaults.valueForKey("name") as! String
    tasksTitle.title = "Tasks for \(name)"
    var y=CGFloat(140)

    for var i=0;i<images.count;i++ {
        print(i)
        buttons.append(UIButton(type: .Custom))
        buttons[i].frame = CGRectMake(60,y,650,100)

        buttons[i].setImage(UIImage(named: "\(images[i]).png"), forState: .Normal)
        buttons[i].tag = i
        buttons[i].addTarget(self, action: "taskPressed:", forControlEvents: UIControlEvents.TouchUpInside)
        self.view.addSubview(buttons[i])
        y+=130
        print(y)
    }

My problem is that it takes about 20 seconds for the buttons to appear and when they do only the first (Add To Inventory) and the last (Scrap Inventory) actually appear. I have tried recreating the view and using normal buttons with the same results. Does anyone have any idea as what my problem might be?

Answer 1

Are you using auto layout ? If you are, it may explain why you are not seeing all your buttons. The other possibility is that some images are not included in your application bundle (which may cause the framework to spend time trying to find them elsewhere) or are very large.

Answer 2

Turns out the reason fro the delay was because of threading. When I enclosed my code in

dispatch_async(dispatch_get_main_queue()){
}

the buttons appeared immediately.