如何在 UIAlertController 的中心显示活动指示器? [英] How to display activity indicator in center of UIAlertController?

问题描述

我目前有一个 UIAlertController 显示在屏幕上.警报的视图应该只显示 2 个元素，一个标题和一个位于警报中心的 UIActivityIndi​​catorView.下面是显示警报及其元素的函数.

I currently have a UIAlertController being displayed on the screen. The view of the alert should only display 2 elements, a title and a UIActivityIndicatorView in the center of the alert. Below is the function that displays the alert and its elements.

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
    }

然而，活动指示器并不显示在视图的中心，实际上它显示在屏幕的右下方，远离视图.这是什么原因?

However, the activity indicator doesn't display in the center of the view, in fact it displays in the bottom right of the screen, far off of the view. What is the reason for this?

我知道我可以硬编码指标位置的数字，但我希望警报在具有多种屏幕尺寸和方向的多个设备上工作.

I understand that I can hardcode numbers for the indicator's position, but I want the alert to work on multiple devices with multiple screen sizes and orientations.

推荐答案

请务必在创建视图时设置 frame 属性.

Be sure to set the frame property when you're creating a view.

func displaySignUpPendingAlert() -> UIAlertController {
        //create an alert controller
        let pending = UIAlertController(title: "Creating New User", message: nil, 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.isUserInteractionEnabled = false // required otherwise if there buttons in the UIAlertController you will not be able to press them
        indicator.startAnimating()

        self.presentViewController(pending, animated: true, completion: nil)

        return pending
}

致@62Shark:

let pending = UIAlertController(title: "Creating New User", message: nil, 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]|", options: nil, metrics: nil, views: views)
pending.view.addConstraints(constraints)

indicator.userInteractionEnabled = false
indicator.startAnimating()

self.presentViewController(pending, animated: true, completion: nil)

这篇关于如何在 UIAlertController 的中心显示活动指示器?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！