我目前在屏幕上显示一个UIAlertController.警报的视图只应在警报的中心显示2个元素,一个标题和一个UIActivityIndicatorView.以下是显示警报及其元素的功能.
func displaySignUpPendingAlert() -> UIAlertController {
//Create the UIAlertController
let pending = UIAlertController(title: "Creating New User",message: nil,preferredStyle: .Alert)
//Create the activity indicator to display in it.
let indicator = UIActivityIndicatorView(frame: CGRectMake(pending.view.frame.width / 2.0,pending.view.frame.height / 2.0,20.0,20.0))
indicator.center = CGPointMake(pending.view.frame.width / 2.0,pending.view.frame.height / 2.0)
//Add the activity indicator to the alert's view
pending.view.addSubview(indicator)
//Start animating
indicator.startAnimating()
self.presentViewController(pending,animated: true,completion: nil)
return pending
}
但是,活动指示器不会显示在视图的中心,实际上它显示在屏幕的右下方,远离视图.这是什么原因？
编辑：我明白,我可以硬编码为指标的位置,但我希望警报工作在多个设备与多个屏幕尺寸和方向.
解决方法
创建视图时,请确保设置frame属性.
func displaySignUpPendingAlert() -> UIAlertController {
//create an alert controller
let pending = UIAlertController(title: "Creating New User",preferredStyle: .Alert)
//create an activity indicator
let indicator = UIActivityIndicatorView(frame: pending.view.bounds)
indicator.autoresizingMask = [.FlexibleWidth,.FlexibleHeight]
//add the activity indicator as a subview of the alert controller's view
pending.view.addSubview(indicator)
indicator.userInteractionEnabled = false // required otherwise if there buttons in the UIAlertController you will not be able to press them
indicator.startAnimating()
self.presentViewController(pending,completion: nil)
return pending
}
到@ 62Shark：
let pending = UIAlertController(title: "Creating New User",preferredStyle: .Alert)
let indicator = UIActivityIndicatorView()
indicator.setTranslatesAutoresizingMaskIntoConstraints(false)
pending.view.addSubview(indicator)
let views = ["pending" : pending.view,"indicator" : indicator]
var constraints = NSLayoutConstraint.constraintsWithVisualFormat("V:[indicator]-(-50)-|",options: nil,metrics: nil,views: views)
constraints += NSLayoutConstraint.constraintsWithVisualFormat("H:|[indicator]|",views: views)
pending.view.addConstraints(constraints)
indicator.userInteractionEnabled = false
indicator.startAnimating()
self.presentViewController(pending,completion: nil)
