I have looked through the developer library and found much useful info but still no answer to my question.
The question: Is it possible to have my app run primarily in the background, monitoring the audio route of the phone in general, and reacting to any change in the route with whichever code I choose?
I understand that I must keep within the guidelines of apps running in the background and providing a useful service.
Also note that this app would not have any audio session of its own, it does not need to play or record audio, only monitor the route change (e.g. headset being unplugged).
Hope someone here knows more than I do and can give me a tip!
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I've looked through all the posts online and the Apple Developer Documentation, but nothing seems to comment on this. I want to be able to live-record the audio coming from, say, Spotify or another app that's running in the background, and process this audio data in my own app. This seems to be possible on Android.
I haven't actually coded it out yet but I've read through the documentation fully and previous stackoverflow posts.
I know the iPhone responds to "hey Siri". Is there similar features that I can use in my app to listen for certain sounds? If so what is the name of the iOS framework to use?
No, there is no API for that. Hey Siri is part of the OS and has hardware-level support. Your app can only use the microphones while it’s running; there is support for keeping the app alive while it’s recording audio, but the battery impact would be severe—the device can’t go to sleep—so it would be extremely unlikely to pass app review. That said, if you’d like API support to be added in future, please file an enhancement request with the use case you have in mind.
Yes sure, you can implement a recorder that records from the microphone and then you check anything you may need from recorded files.
Btw, what do you mean by certain sounds?
I think it sounds a bit tricky so please elaborate on your question. What's the business reason? How will you perform "listen for certain sounds"? How do you check it for being "certain". I think it's quite a hard thing to do using iOS but maybe I got your question wrong.
UPDATE: According to your comment: yeah it's possible but not like "hey ios check if it's a gunshot" :)))
But I think you can do it by checking the volume of the sound. If it is loud then it's a gunshot. I think it will work since user will use it on purpose. Check this link.
Also, I saw a similar app for gun shooters. So I'm sure it's doable:)
So shortly: find the way to: 1. use microphone. 2. Listen to sounds. 3. Check the sound for volume/length 4. Try detecting by testing
PS: Be careful with shooting while coding :)
If your "certain" sounds are referring to spoken words. Apple has the Speech Recognition framework for determining particular words.
If you are trying to measure perhaps a particular frequency however, Like many guitar tuner apps use or other music recording type app, I would recommend checking in depth AVFoundation 's guide to audio engineering.
I am relatively new to iOS app development and I'm just trying to figure out some things that, to me, are more abstract. How do apps know when other apps start? The closest example I can think of to what I'm trying to ask is when music is playing in the background and you open another app that has sound and the music stops. Is that the new app taking authority or is there inter app communication? If there is communication how does that communication work? Like is it a message that could be accessed or what?
Sorry if that didn't make much sense, I tried to elaborate the best I could. I couldn't find anything on this on apple's developer website. Thanks in advance!
There is no inter-app communication. Each app is living in its own world, and as far as your app is concerned, it's the only app on the phone. The way communication happens is that an app talks to the system, and the system talks to your app. The way the system sends messages to your app is usually in the delegate of the framework you're working with. In your example, opening your app to play audio will send a message to the system, and the system will tell the other app to stop audio playback. That other app has no idea it was your app that initiated the stop. Another example is the AppDelegate. The app delegate will send your app messages such as application:didFinishLaunchingWithOptions:, which in this method is where you do custom initialization of the app or applicationWillResignActive: which is normally sent when the user presses the home button or receives a phone call, so here you might want to save your game, etc.
In fact the iOS system is quite complicated, much to complicated to be explained in detail here so I highly suggest reading the Apple Developer Documentation, some of it can be a little dry, but they do their best to be coherent with even absolute beginners.
I have a question about running an app in the background.
I know about how to do it, but Apple does not like the way I'm doing it.
To get you on the same page, I have a security app, and I need to it monitor the device even when it is in the background. It is sort of like a burglar alarm.
I was using background audio mode, thinking it would be okay because I will be playing a sound when it is triggered. Needless to say, Apple didn't like that.
So I added a ping! It pings while active, therefor playing background audio while in the background.
Once again, they didn't like that either.
My app monitors the accelerometer as well (but not always, only when chosen by the user).
My question is, how are apps like Skype, and other similar apps able to turn the status bar red, and stay in the background? (Even some alarm apps will do this, without playing any audio or anything).
Also I can't use the notification system because it does not update fast enough if I'm monitoring the battery level. For my app I need immediate response.
I have also searched around tirelessly for this answer before I posted my question (the answers I have found, do not work for me..) :(
I would greatly appreciate any insight on this, Thanks in advance!
(If you need anymore information, please ask!)
From what I can tell from their documentation, it seems that the only way you can maintain a persistent background connection is by using one of their seven background mode keys, which I can see you've been trying since you registered for background audio. I know some alarm apps as well that use this feature (e.g. Sleep Cycle), and my assumption is that they are also using background audio mode, considering the other six modes are not remotely close to what they would need it for.
I think Apple's reasoning might be that these apps are allowed to do so, because their app is designed to be used when the user is not using the phone actively (i.e. when they're sleeping), and requires the audio to wake the user up, whereas if you are running a security app that wants to be active at all times, it may interfere with other features the user may use like Skype. The red bar will also persist at the top of the device at all times when the user is using it, which they may mistake for something that is still playing since usually when a red bar appears it means to the user that they are still actively using something. Again, I think wake-up alarm apps and others like them that aren't using persistent audio are able to get away with this since they are designed for use when the phone is inactive, so having the persistent red bar when the app is not visible is less of an issue.
In some other cases, like Nike+ (discussed here) and likely pedometers, they seem to be using the location background mode, since they often also track where you went and need to know distance. In that discussion I linked to, it looks like others were able to get accelerometer updates by registering for a background mode that applied to them. Have you tried registering for location movements? One downside I can see to that is it might drain battery life quicker, but if you check location infrequently it might not be too bad? Another is that I don't think you can directly play audio when in location background mode, but you could try to trigger a sound notification? :) That might be a nice workaround for it if that works for your app.
Again, the reasoning I have for why these apps are able to do it is just based on how I've seen other apps operating, and Apple may have different reasons for why it accepts them, but that was my best way of thinking why your app got rejected for using those modes while the others are able to do it. If location isn't what you're looking for, unfortunately I'm not sure from what it sounds like your app is doing that you'd be able to operate it continuously in the background in the way you're expecting.
Being responsive is a need for every app. Users want to have apps which have their content ready when they open it, so developers should use Background Modes to make their apps more user friendly.
Turning on the Background Modes capability
Go to Xcode and open your project.
In your app target, navigate to Capabilities tab.
Turn on Background Modes.
Background Fetch
Background fetch is a new mode that lets your app appear always up-to-date with the latest information while minimizing the impact on battery. You could download feeds within fixed time intervals with this capability.
To get started:
1- Check Background Fetch in capabilities screen in Xcode.
2- In application(_:didFinishLaunchingWithOptions:) method in AppDelegate,
Reference: https://medium.com/#javedmultani16/background-modes-in-ios-3da25b9e6474
You can use background modes only if you actively use the activity that keeps the app awake: e.g. continuously playing audio is a valid use of the audio background key. They'll look pretty hard at whether you really need the access you request, and if not they'll reject you (as you've already found out), as background services drain the battery considerably more than others.
From the docs:
These keys should be used sparingly and only by apps providing the indicated services.
Short story: I think you're out of luck with your proposed implementation.
How to create an app that functions like demon process at the background?
Is this possible?
Generally not. Apps can't fork processes, the only thing you can do is ask for some time (max 10 minutes) to resume tasks after your app was send to background. For specific use cases (audio playing, location tracking, VOIP) there are well defined exceptions to this rule.
No. Apple only allows specific hooks for background functions, but you cannot - without jailbreaking the device - run anything in the background "generically".
Better think of Multitasking as fast-app-switching with some extras. I recently did a little writeup of this on my blog trying to shed some light on a topic in the Apple discussion forums.
Maybe you find it useful to understand more of the backgrounds. It can be found here: http://www.danielschneller.com/2010/11/ios-421-battery-drain-on-ipad.html