Q: How to programmatically add a simple default loading(progress) bar in iphone app I am using http communication in My iPhone app. I want to show a progress bar while it is loading data from server. How can I do it programmatically?
I just want a default progress-bar. Nothing fancy, like in android we do ProgressDialog.show();, is there any one liner for showing progress-bar in iphone?

A: UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
indicator.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
indicator.center = self.view.center;    
[self.view addSubview:indicator];
[indicator bringSubviewToFront:self.view];
[UIApplication sharedApplication].networkActivityIndicatorVisible = TRUE;

Write below code when you want to show indicator  
[indicator startAnimating];

write below code when you want to hide indicator  
[indicator stopAnimating];


A: UIProgressView is the class you are looking for: Apple Docs
You need to use the setProgress:animated: method to updated the shown progress. Most likely where you handle received data from the network.

A: You can use IOS in-built UIProgressView. Below is code snippet:
UIProgressView *progressView = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault];
[self.view addSubview:progressView];
[progressView setProgress:50.0];

You can use setFrame: for positioning of progress bar on view.

A: Try below code
float progress;

//components
UIProgressView *progressBar;
progressBar=[[UIProgressView alloc]initWithProgressViewStyle:UIProgressViewStyleDefault];
[progressBar setFrame:CGRectMake(30.0, 75.0, 200.0, 80.0)];

int prog=progress*100;
progressStr=[NSString stringWithFormat:@"%d%%",prog];
[progressBar setProgress:progress];


A: Translating @Hiren's answer to Swift
 var indicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)
 indicator.frame = CGRect(x: 0, y: 0, width: 40, height: 40)
 indicator.center = view.center
 self.view.addSubview(indicator)
 self.view.bringSubview(toFront: indicator)
 UIApplication.shared.isNetworkActivityIndicatorVisible = true

Show indicator
indicator.startAnimating()

Stop indicator
indicator.stopAnimating()


A: I know this is an older question but I've written a global static method for doing this type of thing from any view, based on the above answers.
Main updates are:


*

*support optional opaque overlay behind the activity indicator 

*use default frame sizing for the activity indicator 

*use .WhiteLarge indicator style


In my AppHelper.swift:
static func showActivityIndicator(view: UIView, withOpaqueOverlay: Bool) {

    // this will be the alignment view for the activity indicator
    var superView: UIView = view

    // if we want an opaque overlay, do that work first then put the activity indicator within that view; else just use the passed UIView to center it
    if withOpaqueOverlay {
        let overlay = UIView()
        overlay.frame = CGRectMake(0.0, 0.0, view.frame.width, view.frame.height)
        overlay.layer.backgroundColor = UIColor.blackColor().CGColor
        overlay.alpha = 0.7
        overlay.tag = activityIndicatorOverlayViewTag

        overlay.center = superView.center
        overlay.hidden = false
        superView.addSubview(overlay)
        superView.bringSubviewToFront(overlay)

        // now we'll work on adding the indicator to the overlay (now superView)
        superView = overlay
    }

    let indicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: .WhiteLarge)

    indicator.center = superView.center
    indicator.tag = activityIndicatorViewTag
    indicator.hidden = false

    superView.addSubview(indicator)
    superView.bringSubviewToFront(indicator)

    indicator.startAnimating()

    // also indicate network activity in the status bar
    UIApplication.sharedApplication().networkActivityIndicatorVisible = true
}

static func hideActivityIndicator(view: UIView) {

    // stop the network activity animation in the status bar
    UIApplication.sharedApplication().networkActivityIndicatorVisible = false

    // remove the activity indicator and optional overlay views
    view.viewWithTag(activityIndicatorViewTag)?.removeFromSuperview()
    view.viewWithTag(activityIndicatorOverlayViewTag)?.removeFromSuperview()
}


A: Swift 5.x version of @enrique7mc's Swift code:
var indicator: UIActivityIndicatorView = UIActivityIndicatorView(style: UIActivityIndicatorView.Style.gray)
indicator.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0)
indicator.center = view.center
view.addSubview(indicator)
indicator.bringSubviewToFront(view)
UIApplication.shared.isNetworkActivityIndicatorVisible = true

Start it with
indicator.startAnimating()

Stop it with
indicator.stopAnimating()

This adds a small ActivityIndicator (turning circle, Apple's documentation) to the middle of the screen and to the status bar. The first one will be cleared once you switch to a different ViewController, while the one in the status bar won't - you have to manually disable it.

A: Try MBProgressHUD. 
It's pretty simple, got several progress animation options, and able to add some customization. It displays fullscreen. And it should work with any recent iOS versions.
Or try LDProgressView if you want something more fancy :) It somehow looks like OSX progress bar.

A: Swift 5.x Version
import UIKit
class SKLoader: NSObject {
    
    static let sharedInstance = SKLoader()

    let indicator: UIActivityIndicatorView? = UIActivityIndicatorView(style: UIActivityIndicatorView.Style.medium)

    let screen = UIScreen.main.bounds

    var appDelegate: SceneDelegate {
        guard let sceneDelegate = UIApplication.shared.connectedScenes
            .first!.delegate as? SceneDelegate else {
                fatalError("sceneDelegate is not UIApplication.shared.delegate")
        }
        return sceneDelegate
    }
    
    var rootController:UIViewController? {
        guard let viewController = appDelegate.window?.rootViewController else {
            fatalError("There is no root controller")
        }
        return viewController
    }
    
    func show() {
        indicator?.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0)
        indicator?.frame.origin.x = (screen.width/2 - 20)
        indicator?.frame.origin.y = (screen.height/2 - 20)
        rootController?.view.addSubview(indicator!)
        indicator?.startAnimating()
    }
    
    func hide() {
        DispatchQueue.main.async {
            self.indicator?.stopAnimating()
            self.indicator?.removeFromSuperview()
        }
    }
}

Sample Usage:
//To Show
SKLoader.sharedInstance.show()
//To Hide
SKLoader.sharedInstance.hide()
=======

A: I'd recommend using NSURLConnection. The methods you would need are:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
  [self.resourceData setLength:0];
  self.filesize = [NSNumber numberWithLongLong:[response expectedContentLength]];
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
  [self.resourceData appendData:data];
  NSNumber *resourceLength = [NSNumber numberWithUnsignedInteger:[self.resourceData length]];
  self.progressBar.progress = [resourceLength floatValue] / [self.filesize floatValue];
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
  self.progressBar.hidden = YES;
}

And the header file:
@property (nonatomic, retain) UIProgressView *progressBar;
@property (nonatomic, retain) NSMutableData *resourceData;
@property (nonatomic, retain) NSNumber *filesize;

Hope it helps

A: To maintain this question totally updated I have translated @enrique7mc's answer to Swift3.0 following his translation from @Hiren's answer.
var indicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)
indicator.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0)
indicator.center = view.center
view.addSubview(indicator)
indicator.bringSubview(toFront: view)
UIApplication.shared.isNetworkActivityIndicatorVisible = true

To start and stop the progress bar is in the same way that @enrique7mc pointed out.
indicator.startAnimating()
indicator.stopAnimating()


A: I wanted to post a solution I created which will show a progress bar in a separate window to show progress with results that could be listed off.
Attached is an image below of what it looks like.

Compatibility: Swift 3
Features: Threaded codeToRun & Cancel + Done Button.  Automatically shows progress amount left if you wanted with updateProgress function.
The code is very simple and easy to modify, just a storyboard and a viewcontroller.  


*

*Use the XML below and save with the final name I suggest below somewhere in your project.


ProgressWindow.storyboard
<?xml version="1.0" encoding="UTF-8"?>
<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="11542" systemVersion="16B2555" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
    <device id="retina4_7" orientation="portrait">
        <adaptation id="fullscreen"/>
    </device>
    <dependencies>
        <deployment identifier="iOS"/>
        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="11524"/>
        <capability name="Constraints to layout margins" minToolsVersion="6.0"/>
        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
    </dependencies>
    <scenes>
        <!--Progress-->
        <scene sceneID="5gE-ws-FsC">
            <objects>
                <viewController storyboardIdentifier="progressWindow" title="Progress" id="IB9-Dc-dCV" customClass="ProgressWindowViewController" customModule="WorkOrders" customModuleProvider="target" sceneMemberID="viewController">
                    <layoutGuides>
                        <viewControllerLayoutGuide type="top" id="Lvc-9P-nmJ"/>
                        <viewControllerLayoutGuide type="bottom" id="xJS-yG-jWM"/>
                    </layoutGuides>
                    <view key="view" contentMode="scaleToFill" id="iDk-68-mde">
                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        <subviews>
                            <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Please Wait..." textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="9ui-W7-ucD">
                                <rect key="frame" x="16" y="84" width="343" height="21"/>
                                <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                <nil key="highlightedColor"/>
                            </label>
                            <progressView opaque="NO" contentMode="scaleToFill" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="ov7-yH-A5z">
                                <rect key="frame" x="16" y="113" width="343" height="2"/>
                            </progressView>
                            <textView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" editable="NO" text="Starting Up..." textAlignment="natural" selectable="NO" translatesAutoresizingMaskIntoConstraints="NO" id="bwA-YT-FcE">
                                <rect key="frame" x="16" y="123" width="343" height="464"/>
                                <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                <textInputTraits key="textInputTraits" autocapitalizationType="sentences"/>
                            </textView>
                            <navigationBar contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="RPs-Mo-Cfx">
                                <rect key="frame" x="-4" y="20" width="383" height="44"/>
                                <items>
                                    <navigationItem title="Starting Sync..." id="Y87-LY-5o5">
                                        <barButtonItem key="rightBarButtonItem" title="Cancel" id="AD3-in-E6j">
                                            <connections>
                                                <action selector="cancelNavItemButtonActionWithSender:" destination="IB9-Dc-dCV" id="IF1-MG-v2x"/>
                                            </connections>
                                        </barButtonItem>
                                    </navigationItem>
                                </items>
                            </navigationBar>
                            <button opaque="NO" contentMode="scaleToFill" enabled="NO" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="6lh-KK-lX1">
                                <rect key="frame" x="113" y="595" width="150" height="42"/>
                                <fontDescription key="fontDescription" type="system" pointSize="25"/>
                                <state key="normal" title="Done"/>
                                <state key="disabled" title="Please Wait..."/>
                                <connections>
                                    <action selector="doneButtonActionWithSender:" destination="IB9-Dc-dCV" eventType="touchUpInside" id="KQH-Th-NAC"/>
                                </connections>
                            </button>
                        </subviews>
                        <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                        <constraints>
                            <constraint firstAttribute="leadingMargin" secondItem="ov7-yH-A5z" secondAttribute="leading" id="9Gm-bd-GY6"/>
                            <constraint firstItem="xJS-yG-jWM" firstAttribute="top" secondItem="bwA-YT-FcE" secondAttribute="bottom" constant="20" id="CT1-0k-Skt"/>
                            <constraint firstItem="6lh-KK-lX1" firstAttribute="top" secondItem="bwA-YT-FcE" secondAttribute="bottom" constant="8" symbolic="YES" id="Fb8-eP-lxu"/>
                            <constraint firstItem="RPs-Mo-Cfx" firstAttribute="leading" secondItem="iDk-68-mde" secondAttribute="leadingMargin" constant="-20" id="JSY-Na-oAF"/>
                            <constraint firstItem="xJS-yG-jWM" firstAttribute="top" secondItem="6lh-KK-lX1" secondAttribute="bottom" constant="30" id="NHY-fO-W26"/>
                            <constraint firstAttribute="trailingMargin" secondItem="RPs-Mo-Cfx" secondAttribute="trailing" constant="-20" id="QxH-pj-oOA"/>
                            <constraint firstItem="RPs-Mo-Cfx" firstAttribute="top" secondItem="Lvc-9P-nmJ" secondAttribute="bottom" id="VIf-63-vaw"/>
                            <constraint firstAttribute="trailingMargin" secondItem="bwA-YT-FcE" secondAttribute="trailing" id="WxH-hu-ZVQ"/>
                            <constraint firstAttribute="leadingMargin" secondItem="bwA-YT-FcE" secondAttribute="leading" id="XEd-Ba-ZfL"/>
                            <constraint firstItem="bwA-YT-FcE" firstAttribute="top" secondItem="ov7-yH-A5z" secondAttribute="bottom" constant="8" id="Xjr-bH-ILB"/>
                            <constraint firstItem="6lh-KK-lX1" firstAttribute="centerY" secondItem="iDk-68-mde" secondAttribute="centerY" id="ZU1-pD-czP"/>
                            <constraint firstItem="ov7-yH-A5z" firstAttribute="top" secondItem="9ui-W7-ucD" secondAttribute="bottom" constant="8" symbolic="YES" id="avI-Ab-G29"/>
                            <constraint firstAttribute="leadingMargin" secondItem="9ui-W7-ucD" secondAttribute="leading" id="dse-zV-g00"/>
                            <constraint firstItem="6lh-KK-lX1" firstAttribute="centerX" secondItem="iDk-68-mde" secondAttribute="centerX" id="i5Q-oY-DdV"/>
                            <constraint firstAttribute="trailingMargin" secondItem="9ui-W7-ucD" secondAttribute="trailing" id="jqu-1f-IuA"/>
                            <constraint firstItem="9ui-W7-ucD" firstAttribute="top" secondItem="RPs-Mo-Cfx" secondAttribute="bottom" constant="20" id="nrH-ey-Zcm"/>
                            <constraint firstAttribute="trailingMargin" secondItem="ov7-yH-A5z" secondAttribute="trailing" id="qha-Es-6Au"/>
                        </constraints>
                        <variation key="default">
                            <mask key="constraints">
                                <exclude reference="ZU1-pD-czP"/>
                                <exclude reference="CT1-0k-Skt"/>
                            </mask>
                        </variation>
                    </view>
                    <connections>
                        <outlet property="cancelNavButton" destination="AD3-in-E6j" id="SJc-Bc-N6j"/>
                        <outlet property="currentProgressLabel" destination="9ui-W7-ucD" id="zij-yQ-MFX"/>
                        <outlet property="doneButton" destination="6lh-KK-lX1" id="rh2-RF-4ak"/>
                        <outlet property="navItemLabel" destination="Y87-LY-5o5" id="ijO-a7-TrD"/>
                        <outlet property="navigationBar" destination="RPs-Mo-Cfx" id="WEq-F4-Pup"/>
                        <outlet property="theProgressBar" destination="ov7-yH-A5z" id="FUE-9J-iBh"/>
                        <outlet property="theTextView" destination="bwA-YT-FcE" id="1sR-23-NZH"/>
                    </connections>
                </viewController>
                <placeholder placeholderIdentifier="IBFirstResponder" id="TH6-NB-Eos" userLabel="First Responder" sceneMemberID="firstResponder"/>
            </objects>
            <point key="canvasLocation" x="-492" y="1474"/>
        </scene>
    </scenes>
</document>



*Save the following code below into your project with the name ProgressWindowViewController.swift


ProgressWindowViewController.swift
import UIKit

protocol progressWindowDelegate : class{
    var titleToGive : String {get}
    func codeToRun(progressWindowViewController:ProgressWindowViewController)
    var codeToCancel : ()->() {get}
}


class ProgressWindowViewController: UIViewController {

    @IBOutlet weak var theTextView: UITextView!
    @IBOutlet weak var currentProgressLabel: UILabel!
    @IBOutlet weak var theProgressBar: UIProgressView!
    @IBOutlet weak var navItemLabel: UINavigationItem!
    @IBOutlet weak var doneButton: UIButton!
    @IBOutlet weak var cancelNavButton: UIBarButtonItem!
    @IBOutlet weak var navigationBar: UINavigationBar!

    //For showing network activity
    var indicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)

    //Sets delegate
    weak var controllerDelegate:progressWindowDelegate? = nil

    override func viewDidLoad() {
        super.viewDidLoad()

        navItemLabel.title = controllerDelegate!.titleToGive

        //Run on the main thread first then in background thread.
        DispatchQueue.main.async {
            DispatchQueue.global(qos: .background).async{
                self.controllerDelegate?.codeToRun(progressWindowViewController: self)
            }
        }

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func writeToProgressWindow(text:NSMutableAttributedString){
        DispatchQueue.main.async(execute: {
            print("dispatch_queue_get_main_queue -> writeToProgressWindow()")
            self.theTextView.attributedText = text
        })
    }

    func updateNetworkIndicator(active:Bool){
        DispatchQueue.main.async(execute: {
            if(active){
                UIApplication.shared.isNetworkActivityIndicatorVisible = true
            }else{
                UIApplication.shared.isNetworkActivityIndicatorVisible = false
            }
        })
    }

    func updateProgress(updatetext:String,amount:Int,left:Int){
        DispatchQueue.main.async(execute: {
            print("dispatch_queue_get_main_queue -> updatingProgress()")
            self.currentProgressLabel.text = updatetext+" : \(amount) / \(left)"
            self.theProgressBar.setProgress(Float(amount/left), animated: true) //progress is represented as a percentage of the total
        })
    }

    func updateProgressWindowWeFinished(title:String){
        //Enable done button and Disable/Hide Cancel Button.  Add Final Messages
        DispatchQueue.main.async(execute: {
            self.doneButton.isEnabled = true
            self.navItemLabel.title = title
            self.cancelNavButton.isEnabled = false
            self.cancelNavButton.tintColor = UIColor.clear
        })
    }

    @IBAction func cancelNavItemButtonAction(sender: UIBarButtonItem) {
        //Run on the main thread first then in background thread.
        DispatchQueue.main.async {
            DispatchQueue.global(qos: .background).sync{
                print("dispatch_queue_priority_default")
                self.controllerDelegate?.codeToCancel()
            }
            self.dismiss(animated: true, completion: nil)//closes the window.
        }
    }


    @IBAction func doneButtonAction(sender: UIButton) {
        self.dismiss(animated: true, completion: nil)//closes the window.
    }

    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

3.) To use you simply set the view controller which called it to the progressWindowDelegate and supply the needed information to communicate with the popover.

Some example code below if you need it:
SampleViewControllerWithYesButton.swift
class SyncViewController: UIViewController, progressWindowDelegate {

    var codeToCancel = {print("code to cancel")}
    var titleToGive = "Starting Sync..."

    func codeToRun(progressWindowViewController:ProgressWindowViewController) {
        print("code to run")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func yesButtonAction(_ sender: UIButton) {







            let storyboard = UIStoryboard(name: "ProgressWindow", bundle: nil)
            let controller = storyboard.instantiateViewController(withIdentifier: "progressWindow") as! ProgressWindowViewController
            controller.controllerDelegate = self
            self.present(controller, animated: true, completion: nil)


    }

    @IBAction func noButtonAction(_ sender: UIButton) {
        tabBarController?.selectedIndex = 1 //Send them to the list then.
    }


    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

Whatever you put in the codeToRun() will run as a background thread.  To access any of the UI the codeToRun has access to the progressWindowViewController which has been preconfigured to hook up to the UI with these elements at your control.
@IBOutlet weak var theTextView: UITextView!
    @IBOutlet weak var currentProgressLabel: UILabel!
    @IBOutlet weak var theProgressBar: UIProgressView!
    @IBOutlet weak var navItemLabel: UINavigationItem!
    @IBOutlet weak var doneButton: UIButton!
    @IBOutlet weak var cancelNavButton: UIBarButtonItem!
    @IBOutlet weak var navigationBar: UINavigationBar!

I use this in all my projects anytime I'm doing a sync, upload or a time consuming network task.
This also shows the activity indictor as well to show that you are trying to do something.  All of this can be customized as its very easy to look over and understand how it works.  Hopefully this helps save some of you some time quickly getting a progress type window up. 

A: Swift 3 version of @enrique7mc solution
    var indicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)
    indicator.frame = CGRect(x: 0, y: 0, width: 40, height: 40)
    indicator.center = view.center
    view.addSubview(indicator)
    indicator.bringSubview(toFront: view)
    UIApplication.shared.isNetworkActivityIndicatorVisible = true


    indicator.startAnimating()
    indicator.stopAnimating()


A: @hiren's answer translation to Swift4.0
let indicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorView.Style.gray)
        indicator.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0)
        indicator.center = view.center
        view.addSubview(indicator)
        indicator.bringSubviewToFront(view)
        UIApplication.shared.isNetworkActivityIndicatorVisible = true


indicator.startAnimating()
indicator.stopAnimating()


A: I will put in my two cents here as well:
I have created this ARSLineProgress preloader, that you could also test here on Appetize.

A: Add Property
@property (strong, nonatomic) IBOutlet UIActivityIndicatorView *indicator;
To Start Animating
[self.indicator startAnimating];
To Stop Animating
[self.indicator stopAnimating];

A: SwiftUI version
Very crude and simple, not-networked, basic progress indicator. Still not supported by default in SwiftUI, so the UIViewRepresentable is the way to go. Enjoy modifying it to your heart's contents.
struct ActivityIndicatorView: UIViewRepresentable {
    let large: Bool
    @State var enabled: Bool

    func makeUIView(context: Context) -> UIActivityIndicatorView {
        let view = UIActivityIndicatorView(style: large ? .large : .medium)
        return view
    }

    func updateUIView(_ view: UIActivityIndicatorView, context: Context) {
        if enabled {
            view.startAnimating()
        } else {
            view.stopAnimating()
        }
    }
}


A: App Delegate.h
-(void)showLoader;

-(void)hideLoder;

App Delegate.m
@implementation AppDelegate

AppDelegate *app;

-(void)showLoader
{

    if(loaderView== NULL)
    {
        loaderView=[[UIView alloc] initWithFrame:self.window.frame];

        [loaderView setBackgroundColor:[UIColor blackColor]];

        [loaderView setAlpha:0.5];

        spinner = [[UIActivityIndicatorView alloc initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];

        [loaderView addSubview:spinner];

        spinner.center = CGPointMake(loaderView.frame.size.width/2-10, 

        loaderView.frame.size.height/2-10);

        spinner.hidesWhenStopped = YES;  
    }
    [spinner startAnimating];
    [self.window addSubview:loaderView];
    [self.window bringSubviewToFront:spinner];
    [self.window bringSubviewToFront:loaderView];
}

-(void)hideLoder
{       
    if (spinner!= NULL) {           
        [spinner stopAnimating];
    }

    [loaderView removeFromSuperview];
}


now import "AppDelegate.h" class where ever you want to call loader.and you can call the loader like this.
[app showLoader];
and
[app hideLoder];
