I have an ARKit app which allows the user to add a cube to the scene. This works fine and I can see the cube. But when I push the app to the background and then move the device to another location (by walking to a different room) then ARKit session is unable to determine the correct position of my old nodes.
Is there anyway I can find a workaround this problem so that when the app is resumed from coming to foreground from the background then it still remembers the position of the nodes.
UPDATE: I am looking into saving the lat and long for the user and then somehow converting those lat and long to SCNVector3 to put the node.
You probably won't be able to keep the AR running in the background. Apple does not recommend pausing the session or interrupting it and trying to resume:
Avoid interrupting the AR experience. If the user transitions to another fullscreen UI in your app, the AR view might not be an expected state when coming back.
Use the popover presentation (even on iPhone) for auxiliary view controllers to keep the user in the AR experience while adjusting settings or making a modal selection. In this example, the SettingsViewController and VirtualObjectSelectionViewController classes use popover presentation.
The issue is that once the session gets interrupted, the device stops using it's mechanisms that keep track of AR Nodes as well as your location, might have to set up a mechanism that keeps the app running constantly in the background and running the ARSession through that. You might be able to find projects on github that allow for running in the background. Another issue you might face is Apple's limitations with running apps in the background, which is apparently 3 minutes.
If you're at all interested in restarting the AR Session one you came back in, you can see my answer on this thread.
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I have an app that uses ARKit to detect faces and send over the network the coordinates of interest, which works well. I would like this app to run in background, still sending the data over the network, while I would be using another app (almost) fullscreen.
The option 'Enable multiple windows' is activated in info.plist, but as soon as I launch my other app, the ARKit app stops sending information (the app actually probably stops).
Is there a simple way to do this, and at least is this feasible? Thanks!
This is not possible at this point. Camera and AR stuff is disabled at a system level in apps when they are displayed in Slide Over or Split View.
I'd recommend displaying a warning message when Slide Over/Split Screen is being used saying that you should use the app in full screen mode. See this answer under a different question for details.
I have a toy iOS app that's just for me. It's a native wrapper of a web-based WebAssembly-heavy game.
It's one of those where you set a task, and then wait for it to complete. Great for desktop browsers where you can just leave an open window in the corner of the display and work elsewhere.
WKWebView, however, seems to go inactive and stops processing game content when the app is backgrounded. I'd like any way (evil hacks accepted) to keep this from happening, so that the game does not pause or go inactive.
I've tried a number of hacks, including:
attaching the web view to the key window (deprecated in iOS 13 beta)
using an audio session to keep the app alive in the background
pumping the web view with evaluateJavaScript calls on a timer while in the background
...to no avail. Any solutions welcome!
(p.s., I'm aware of a couple other questions like this one, but want to ask my own to manage the bounty and also I'm not sure if the game being WASM makes a difference, vs. the other questions specifically calling out JavaScript)
I am writing an iOS app that keeps and displays the state of a system. It basically shows a light whose color represents state:
green/yellow/red light <==> OK/warning/danger
I'd prefer to show accurate state even when the app is backgrounded, and its snapshot is viewed thru the iOS multitask viewer (the view that looks like a rolodex, which you get after double-clicking the home button). I REALLY don't want to show a snapshot which displays an inaccurate state.
So my question is: can you change the view (or perhaps the app snapshot) while the app is in the background, so that when it's viewed in the multitask view it shows an accurate state.
I've seen that this is not recommended by Apple: from App Programming Guide for iOS
Avoid updating your windows and views. Because your app’s windows and views are not visible when your app is in the background, you should avoid updating them. The exception is in cases where you need to update the contents of a window prior to having a snapshot of your app taken.
However, Apple's music app does just this...if you start playing a playlist, then put the music app into the background, the cover art gets updated as the music app works thru the playlist. So this functionality must be possible somehow.
The best answer I can come up with after a bunch of searching is to alter my app's view to the splash image prior to entering background operation. This would ensure that inaccurate state isn't displayed, but also prevents showing accurate state.
You can change the snapshot view immediately before the snapshot is taken (A banking app, for example might want to obscure personal information), but you cannot continue to update the snapshot from the background once your app is suspended. You may want to adopt this approach in order to avoid displaying an inaccurate state; show nothing rather than stale data.
You might also want to consider some other options, such as a "today" widget that contains the updated status or posting local notifications when there is a significant change in status (such as entering the "red" state).
I'd like to perform an action when the user has their finger held on the screen when my app startups.
To give an example: When the App launches and the launch screen is showing up, the user has a finger on the screen as long as the first ViewController appears. When the first ViewController gets into the viewDidAppear() function, I want to detect, that the users finger is on the screen and perform an action, like f.ex. jumping straight into the lastest received email. Basically this is supposed to be a kind of shortcut to an main action.
Is there any method to detect an already laying finger on the screen? To be exactly I'd like to check for the tap in viewDidAppear()
Unless the nature of Time has changed since the last time I checked, your app cannot detect what the user was doing before the app launched. The app, ex hypothesi, was not running at that time. And the mere presence of a finger on the screen during app launch will not generate a touch event that the app can detect.
The system can detect it, however, since is running before your app launches. That is why Apple added force-touch Shortcuts (for appropriate hardware). The only way you can do what you're asking is to rely on that API. Hardware that lacks this feature will simply have to do without this feature.
(After all, this is how Apple makes money: by trying to make users jealous of hardware they don't have, so that they buy new hardware. You would want to rob Apple of its income by reading this feature backwards onto old hardware, even if you could, now would you?)
First of all I hope don't repeat any topic, I have spent a lot of time reading on internet about this before ask.
I'm developing an app for iOS => 5 and I need get the user location, but I don't need always a great accurate position, so when the app goes to background I change the normal location mode to Significant Location Changes and when the app come to foreground I stop the significant location change mode and get back the normal location mode, that's all goes fine,
my problem is when the app goes to background mode or even the user KILL the app the GPS signal (the purple arrow) still appear ALWAYS, even after restart the device, the only way to make disappear it is un-installing the or disabling the significant location changes when the app goes to background, but I need this mode working when the user goes to background mode, maybe not when the app is killed.
I don't know how to stop the service when the user kill the app... because event "applicationWillTerminate" is not called if you have multitask ON.
My main reason because I don't want the purple arrow appear always, even the app is killed is because I don't want the user think the app is drying the battery... so the user won't want the app installed.
First question: Is normal that the purple arrow appear always, even the app is killed if the Significant location change is enabled for the app?
Second question: Is any way to change this, to stop the service at least when the app is killed to hide the purple arrow?
Thank you all.
Sorry for my english if something is wrong.
After few days researching to be sure about this service, seems like there is NO way to use significant locations change in the background without the arrow in the top bar. I have been testing with different apps and reading through internet and nothing to solve this.
The only ""way to solve"" this is disable multitask mode in the app and disable the significant locations change in the event "applicationWillTerminate" but don't make sense... I'm losing the background location always not only when the app is killed... so is not useful.
It's bad... is a really good service to get locations saving battery but as user and developer I don't want an app that make appear this icon ALWAYS even after the app is killed, as developer I don't want that people uninstall the app for this reason and as normal user I don't know what mean this icon if is normal GPS or Significant locations change and what mean this... if my battery is being drain or not.
The other option to get locations in background task but has a big impact over the battery....
I hope apple fix this in future versions... adding at least a new arrow or showing only when a new location arrive instad of always or allowing to stooped when the app is killed.
All this has been researched over iOS - 6.1
Thanks to all.
When you use the significant location change service, the OS keeps your app running. If the app is in the background and is killed, the OS restarts it, so the purple arrow will always show. When a new location is detected, the app is restarted. From the docs:
If you leave this service running and your app is subsequently suspended or terminated, the service automatically wakes up your app when new location data arrives. At wake-up time, your app is put into the background and given a small amount of time to process the location data. ... To stop the significant change location service, call the stopMonitoringSignificantLocationChanges method.
Hmmm, interesting. I've just seen that problem with another app - seeing the arrow still active made me want to disable location updates for that app so the problem is real. Best thing I can think of is to have some kind of timer to disable the location monitoring after a certain amount of time if that is appropriate for your app.