ios – 如何在UIAlertController的中心显示活动指示器？

概述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UIActivityIndi​​catorView.以下是显示警报及其元素的功能. func displaySignUpPendingAlert() -> UIAlertController { //Create the UIAlertController 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UIActivityIndi​​catorVIEw.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 = falseindicator.startAnimating()self.presentVIEwController(pending,completion: nil)

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