Text To Speech functionality when app is in background mode?

Question

I am working on a TextToSpeech app. I write one paragraph in a UITextField, then I press the Speak button. Sound plays according to the text written in the UITextField.

However, when the app is in background mode, the audio stops playing. How can I continue to play the sound in background mode? Similar to how an audio player can play a song in the background.

I am using the following code for text to speech:

#import "ViewController.h"
#import "Google_TTS_BySham.h"
#import <AVFoundation/AVFoundation.h>

@interface ViewController ()

@property (nonatomic,strong)Google_TTS_BySham *google_TTS_BySham;
@property (nonatomic,strong)IBOutlet UITextField *txtString;

@end

@implementation ViewController

#pragma mark - View Life Cycle

- (void)viewDidLoad {
    [super viewDidLoad];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

#pragma mark - Button Tapped event

- (IBAction)btnSpeakTapped:(id)sender{
    NSString *str = [NSString stringWithFormat:@"%@",_txtString.text];
    self.google_TTS_BySham = [[Google_TTS_BySham alloc] init];
    [self.google_TTS_BySham speak:str];
}

Answer 1

Add the following code in info.plist file...

Application does not run in background : NO

Required background modes : App plays audio or streams audio/video using AirPlay

and then add the following code in AppDelegate.m file

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    [[AVAudioSession sharedInstance] setDelegate:self];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    [[AVAudioSession sharedInstance] setActive:YES error:nil];
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

    UInt32 size = sizeof(CFStringRef);
    CFStringRef route;
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &size, &route);
    NSLog(@"route = %@", route);

    return YES;
}

- (void)remoteControlReceivedWithEvent:(UIEvent *)theEvent {

    if (theEvent.type == UIEventTypeRemoteControl)  {
        switch(theEvent.subtype)        {
            case UIEventSubtypeRemoteControlPlay:
                [[NSNotificationCenter defaultCenter] postNotificationName:@"TogglePlayPause" object:nil];
                break;
            case UIEventSubtypeRemoteControlPause:
                [[NSNotificationCenter defaultCenter] postNotificationName:@"TogglePlayPause" object:nil];
                break;
            case UIEventSubtypeRemoteControlStop:
                break;
            case UIEventSubtypeRemoteControlTogglePlayPause:
                [[NSNotificationCenter defaultCenter] postNotificationName:@"TogglePlayPause" object:nil];
                break;
            default:
                return;
        }
    }
}