Question

我目前在屏幕上显示UIAlertController。警报视图应仅显示2个元素，标题和警报中心的UIActivityIndicatorView。下面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央，实际上它显示在屏幕的右下角，远离视图。这是什么原因？

编辑：据我所知，我可以对指标的位置进行硬编码，但我希望警报可以在多种屏幕尺寸和方向的设备上运行。

Answer 1

确保在创建视图时设置框架属性。

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)

Answer 2

如果有人有兴趣，我将答案转换为目标C：

UIAlertController *pending = [UIAlertController alertControllerWithTitle:nil
                                                               message:@"Please wait...\n\n"
                                                        preferredStyle:UIAlertControllerStyleAlert];
UIActivityIndicatorView* indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
indicator.color = [UIColor blackColor];
indicator.translatesAutoresizingMaskIntoConstraints=NO;
[pending.view addSubview:indicator];
NSDictionary * views = @{@"pending" : pending.view, @"indicator" : indicator};

NSArray * constraintsVertical = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[indicator]-(20)-|" options:0 metrics:nil views:views];
NSArray * constraintsHorizontal = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[indicator]|" options:0 metrics:nil views:views];
NSArray * constraints = [constraintsVertical arrayByAddingObjectsFromArray:constraintsHorizontal];
[pending.view addConstraints:constraints];
[indicator setUserInteractionEnabled:NO];
[indicator startAnimating];
[self presentViewController:pending animated:YES completion:nil];

干杯

Answer 3

TL;博士

所有其他答案都已关闭:)请参阅文档：

重要

UIAlertController类旨在按原样使用，但不是   支持子类化。此类的视图层次结构是私有的   不得修改。

问题

问题不在于UIAlertController。这是一个非常简单的UI，一个或两个堆栈视图，具体取决于您是否希望将UIActivityIndicatorView留在标题标签或标题下。演示动画就是我们想要的。

以下代码基于WWDC会话A Look Inside Presentation Controllers。

重新创建演示控制器：

@interface LOActivityAlertControllerPresentationController : UIPresentationController @end @interface LOActivityAlertControllerPresentationController () @property (nonatomic) UIView *dimmerView; @end @implementation LOActivityAlertControllerPresentationController - (instancetype)initWithPresentedViewController:(UIViewController *)presentedViewController presentingViewController:(UIViewController *)presentingViewController { self = [super initWithPresentedViewController:presentedViewController presentingViewController:presentingViewController]; if (self) { _dimmerView = [[UIView alloc] init]; _dimmerView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight; _dimmerView.backgroundColor = [UIColor colorWithWhite:0 alpha:0.4]; UIView *presentedView = [self presentedView]; presentedView.layer.cornerRadius = 8.0; UIInterpolatingMotionEffect *centerXMotionEffect = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x" type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis]; centerXMotionEffect.minimumRelativeValue = @(-10.0); centerXMotionEffect.maximumRelativeValue = @(10.0); UIInterpolatingMotionEffect *centerYMotionEffect = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y" type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis]; centerYMotionEffect.minimumRelativeValue = @(-10.0); centerYMotionEffect.maximumRelativeValue = @(10.0); UIMotionEffectGroup *group = [[UIMotionEffectGroup alloc] init]; group.motionEffects = [NSArray arrayWithObjects:centerXMotionEffect, centerYMotionEffect, nil]; [presentedView addMotionEffect:group]; } return self; } - (CGRect)frameOfPresentedViewInContainerView { UIView *containerView = [self containerView]; UIView *presentedView = [self presentedView]; CGSize size = [presentedView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize]; CGRect frame = CGRectZero; frame.origin = CGPointMake(CGRectGetMidX([containerView frame]) - (size.width / 2.0), CGRectGetMidY([containerView frame]) - (size.height / 2.0)); frame.size = size; return frame; } - (void)presentationTransitionWillBegin { UIViewController *presentingViewController = [self presentingViewController]; UIView *containerView = [self containerView]; UIView *presentedView = [self presentedView]; UIView *dimmerView = [self dimmerView]; dimmerView.alpha = 0.0; dimmerView.frame = [containerView bounds]; [containerView insertSubview:dimmerView atIndex:0]; presentedView.center = [containerView center]; [[presentingViewController transitionCoordinator] animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) { dimmerView.alpha = 1.0; } completion:NULL]; } - (void)containerViewWillLayoutSubviews { [super containerViewWillLayoutSubviews]; UIView *containerView = [self containerView]; UIView *presentedView = [self presentedView]; UIView *dimmerView = [self dimmerView]; dimmerView.frame = [containerView bounds]; presentedView.frame = [self frameOfPresentedViewInContainerView]; } - (void)dismissalTransitionWillBegin { UIViewController *presentingViewController = [self presentingViewController]; UIView *dimmerView = [self dimmerView]; [[presentingViewController transitionCoordinator] animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) { dimmerView.alpha = 0.0; } completion:NULL]; } @end

动画过渡：

@interface LOActivityAlertControllerAnimatedTransitioning : NSObject <UIViewControllerAnimatedTransitioning> @property (getter=isPresentation) BOOL presentation; @end @implementation LOActivityAlertControllerAnimatedTransitioning - (void)animateTransition:(nonnull id<UIViewControllerContextTransitioning>)transitionContext { UIView *containerView = [transitionContext containerView]; UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey]; UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey]; if (_presentation) { [containerView addSubview:toView]; toView.transform = CGAffineTransformMakeScale(1.6, 1.6); toView.alpha = 0.0; [UIView animateWithDuration:0.2 animations:^{ toView.alpha = 1.0; toView.transform = CGAffineTransformIdentity; } completion:^(BOOL finished) { [transitionContext completeTransition:YES]; }]; } else { [UIView animateWithDuration:0.2 animations:^{ fromView.alpha = 0.0; } completion:^(BOOL finished) { [fromView removeFromSuperview]; [transitionContext completeTransition:YES]; }]; } } - (NSTimeInterval)transitionDuration:(nullable id<UIViewControllerContextTransitioning>)transitionContext { return 0.2; } @end

示例UIViewController子类，与XIB一起品尝：

@interface LOActivityAlertController : UIViewController <UIViewControllerTransitioningDelegate> @property (nonatomic, strong) IBOutlet UIActivityIndicatorView *activityIndicatorView; @property (nonatomic, strong) IBOutlet UILabel *titleLabel; @end @implementation LOActivityAlertController @dynamic title; + (instancetype)alertControllerWithTitle:(NSString *)title { LOActivityAlertController *alert = [LOActivityAlertController new]; alert.title = title; return alert; } - (instancetype)init { self = [super init]; if (self) { self.transitioningDelegate = self; self.modalPresentationStyle = UIModalPresentationCustom; } return self; } - (void)viewDidLoad { [super viewDidLoad]; self.titleLabel.text = self.title; } #pragma mark Properties - (void)setTitle:(NSString *)title { [super setTitle:title]; self.titleLabel.text = title; } #pragma mark UIViewControllerTransitioningDelegate - (UIPresentationController *)presentationControllerForPresentedViewController:(UIViewController *)presented presentingViewController:(UIViewController *)presenting sourceViewController:(UIViewController *)source { LOActivityAlertControllerPresentationController *myPresentation = nil; myPresentation = [[LOActivityAlertControllerPresentationController alloc] initWithPresentedViewController:presented presentingViewController:presenting]; return myPresentation; } - (id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source; { LOActivityAlertControllerAnimatedTransitioning *transitioning = [LOActivityAlertControllerAnimatedTransitioning new]; transitioning.presentation = YES; return transitioning; } - (id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed { LOActivityAlertControllerAnimatedTransitioning *transitioning = [LOActivityAlertControllerAnimatedTransitioning new]; return transitioning; } @end

屏幕录制

Bug Reporter

rdar://37433306：创建UIAlertController表示控制器并转换委托公共API以启用重用。

Answer 4

对于那些喜欢在UIActivityIndicatorView左侧对齐UIAlertController.title的人，这是我在 Swift 中为所有设备工作的解决方案：

let alert = UIAlertController(title: NSLocalizedString("Authenticating...", comment: "Authenticating"), message: nil, preferredStyle: .Alert);
let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
activityIndicator.frame = activityIndicator.frame.rectByOffsetting(dx: 8, dy: (alert.view.bounds.height - activityIndicator.frame.height)/2);
activityIndicator.autoresizingMask = .FlexibleRightMargin | .FlexibleTopMargin | .FlexibleBottomMargin
activityIndicator.color = themeManager().currentTheme.navigationBarTintColor;
activityIndicator.startAnimating();
alert.view.addSubview(activityIndicator);
self.presentViewController(progressAlert, animated: true, completion: nil);

但是，要在视图中心对齐UIActivityIndicatorView，您可以更改如下：

activityIndicator.center = CGPoint(x: (alert.view.bounds.width)/2, y: (alert.view.bounds.height)/2)
activityIndicator.autoresizingMask = .FlexibleLeftMargin | .FlexibleRightMargin | .FlexibleTopMargin | .FlexibleBottomMargin

Answer 5

Apple不鼓励直接对UIAlertController进行子类化，因此我创建了一个显示UIAlertController的类，其中心为UIActivityIndicator，并使用类协议处理取消条件。

import Foundation
import UIKit

protocol BusyAlertDelegate {
    func didCancelBusyAlert()
}


class BusyAlert {

   var busyAlertController: UIAlertController?
   var presentingViewController: UIViewController?
   var activityIndicator: UIActivityIndicatorView?
   var delegate:BusyAlertDelegate?

   init (title:String, message:String, presentingViewController: UIViewController) {
       busyAlertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
       busyAlertController!.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "Cancel Button"), style: UIAlertActionStyle.Cancel, handler:{(alert: UIAlertAction!) in
            delegate?.didCancelBusyAlert()
    }))
        self.presentingViewController = presentingViewController
        activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
        busyAlertController!.view.addSubview(activityIndicator!)
    }

    func display() {
        dispatch_async(dispatch_get_main_queue(), {
               self.presentingViewController!.presentViewController(self.busyAlertController!, animated: true, completion: {
            self.activityIndicator!.translatesAutoresizingMaskIntoConstraints = false
               self.busyAlertController!.view.addConstraint(NSLayoutConstraint(item: self.activityIndicator!, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.busyAlertController!.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0))
            self.busyAlertController!.view.addConstraint(NSLayoutConstraint(item: self.activityIndicator!, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.busyAlertController!.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0))
            self.activityIndicator!.startAnimating()

        })
    })

}

func dismiss() {
    dispatch_async(dispatch_get_main_queue(), {
        self.busyAlertController?.dismissViewControllerAnimated(true, completion: nil)
    })
}

}

我建议使用lazy var来初始化类。

lazy var busyAlertController: BusyAlert = {
        let busyAlert = BusyAlert(title: "Lengthy Task", message: "Please     wait...", presentingViewController: self)
        busyAlert.delegate = self
        return busyAlert
        }()

以下是示例代码的链接：https://github.com/cgilleeny/BusyAlertExample.git

Answer 6

在swift：

SELECT 
    CASE WHEN ROW_NUMBER() OVER (PARTITION BY Id ORDER BY Id) = 1 THEN Id ELSE Null END As Id,
    Comments, Type
FROM
    yourTable

如果您有工具栏或navController，您可能想要移动点，否则，中心是中心......

如果您仍然遇到问题，或许this教程会有所帮助。如果您尝试将其置于表格视图控制器中，this答案可能会有所帮助。

Answer 7

我必须实施NSLayoutConstraint以将UIActivityIndicatorView置于UIAlertController的中心

Swift ：

let loadingAlertController: UIAlertController = UIAlertController(title: "Loading", message: nil, preferredStyle: .alert)
let activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView(style: .gray)
activityIndicator.translatesAutoresizingMaskIntoConstraints = false

loadingAlertController.view.addSubview(activityIndicator)

let xConstraint: NSLayoutConstraint = NSLayoutConstraint(item: activityIndicator, attribute: .centerX, relatedBy: .equal, toItem: loadingAlertController.view, attribute: .centerX, multiplier: 1, constant: 0)
let yConstraint: NSLayoutConstraint = NSLayoutConstraint(item: activityIndicator, attribute: .centerY, relatedBy: .equal, toItem: loadingAlertController.view, attribute: .centerY, multiplier: 1.4, constant: 0)

NSLayoutConstraint.activate([ xConstraint, yConstraint])
activityIndicator.isUserInteractionEnabled = false
activityIndicator.startAnimating()

let height: NSLayoutConstraint = NSLayoutConstraint(item: loadingAlertController.view, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 80)
loadingAlertController.view.addConstraint(height);

self.present(loadingAlertController, animated: true, completion: nil)

结果：

Answer 8

Swift 5.0解决方案

let alert = UIAlertController(title: "Sender ...", message: nil, preferredStyle: .alert)
let activityIndicator = UIActivityIndicatorView(style: .gray)
activityIndicator.translatesAutoresizingMaskIntoConstraints = false
activityIndicator.isUserInteractionEnabled = false
activityIndicator.startAnimating()

alert.view.addSubview(activityIndicator)
alert.view.heightAnchor.constraint(equalToConstant: 95).isActive = true

activityIndicator.centerXAnchor.constraint(equalTo: alert.view.centerXAnchor, constant: 0).isActive = true
activityIndicator.bottomAnchor.constraint(equalTo: alert.view.bottomAnchor, constant: -20).isActive = true

present(alert, animated: true)

Answer 9

我有同样的问题，使用框架定位对我不起作用。 Yimin Lin的答案对我来说非常接近，但我只想提出一种使用非视觉格式约束的替代方案：

//...
indicator.setTranslatesAutoresizingMaskIntoConstraints(false)
alert.view.addSubview(indicator)

alert.view.addConstraint(NSLayoutConstraint(item: indicator, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: alert.view, attribute: attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0))
alert.view.addConstraint(NSLayoutConstraint(item: indicator, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: alert.view, attribute: attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0))
//...

Answer 10

转换@ petesalt对Swift 3的回答：

let pending = UIAlertController(title: "Saving, please wait...", message: nil, preferredStyle: .alert)

let indicator = UIActivityIndicatorView()
indicator.translatesAutoresizingMaskIntoConstraints = false
pending.view.addSubview(indicator)

let views = ["pending" : pending.view, "indicator" : indicator]

var constraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[indicator]-(-50)-|", options: NSLayoutFormatOptions.alignAllCenterY, metrics: nil, views: views)
constraints += NSLayoutConstraint.constraints(withVisualFormat: "H:|[indicator]|", options: NSLayoutFormatOptions.alignAllCenterX, metrics: nil, views: views)
pending.view.addConstraints(constraints)

indicator.isUserInteractionEnabled = false
indicator.startAnimating()

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

Answer 11

Swift 3及更高版本的这种方式如何：

func showActivityIndiactorViewController(title: String) -> UIAlertController {
    let pending = UIAlertController(title: "", message: nil, preferredStyle: .alert)
    let heightConstraint:NSLayoutConstraint = NSLayoutConstraint(item: pending.view, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: self.view.frame.height * 0.10)
    pending.view.addConstraint(heightConstraint)

    let label = UILabel()
    label.text = title
    label.textColor = UIColor.black
    label.sizeToFit()

    let space = UIView(frame: CGRect(x: 0, y: 0, width: 8, height: 8))

    let indicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
    indicator.isUserInteractionEnabled = false
    indicator.startAnimating()

    let width = Int(label.frame.size.width + indicator.frame.size.width + space.frame.size.width)

    let view = UIStackView(arrangedSubviews: [indicator, space, label])
    view.axis = .horizontal
    view.frame = CGRect(x: 20, y: 0, width: width, height: Int(heightConstraint.constant))
    pending.view.addSubview(view)

    let widthConstraint:NSLayoutConstraint = NSLayoutConstraint(item: pending.view, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.greaterThanOrEqual, toItem: view, attribute: NSLayoutAttribute.width, multiplier: 1, constant: CGFloat(width))
    pending.view.addConstraint(widthConstraint)

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

    return pending
}

Answer 12

试试这个：

activityView.center = CGPointMake(self.view.bounds.size.width/2.0, self.view.bounds.size.height / 2.0)

此外，您还需要检查横向模式并反转宽度和高度。

if(landscapeMode)activityView.center = CGPointMake(self.view.bounds.size.height/2.0, self.view.bounds.size.width / 2.0)

也许你可以获得警报视图位置？

alert.view.frame.origin.x
alert.view.frame.origin.y

并使用它来动态放置您的活动视图，即使用变量？

当然，您可能还希望将大小除以2并添加它以使其居中。

alert.view.frame.size.height
alert.view.frame.size.width

Answer 13

试试这段代码。

UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil
                                    message:@"Creating new user\n\n\n"
                             preferredStyle:UIAlertControllerStyleAlert];

UIActivityIndicatorView *loader = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
loader.center = CGPointMake(130.5, 65.5);
loader.color = [UIColor blackColor];
[loader startAnimating];
[alert.view loader];
[self presentViewController:alert animated:NO completion:nil];

如何在UIAlertController的中心显示活动指示器？

13 个答案:

TL;博士

问题

屏幕录制

Bug Reporter