I would like to know if I can make an app running on background that detects when power button is pressed and runs a app action that can ignore power button actions. Thanks
A stock (i.e. not jailbroken) iOS device's apps cannot interrupt the power button.
You can do some actions when the app is exited using applicationDidEnterBackground. If you need to prevent users from exiting an application for something like a kiosk, you can turn on Guided Access mode.
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Is it possible to somehow get a callback when the user presses on the physical power button on iOS? Just to make sure, I am not actually trying to change the behaviour of the power button, I just need to know when it was pressed.
Here is some extra info to explain why I need this callback. Our app uses a guided access mode to lock students in test and although guided access allows locking the device via the power button, that lock, unfortunately, causes our sockets to disconnect so we do not allow that. So what I need now is to detect the power button press so I can implement a fake lock in our app where I will dim the display and show a black image on top to save some battery power.
How can I detect Home button long press like 4 second or more event in my app which is already running in background? Is it possible to so because app is already running in background and if user long press home button of the device for 4 second or more can i detect the event in my background running app and if possible than will Apple approve this for app store?
No that is not possible. As you should know, a long press on the home button brings up Siri. Your app would interfere with that. Also, I don't believe Apple allows access to the home button event like that.
Lastly; while your app is in the background, it goes into a suspend state after a short while and no events run. The only thing the app can do is receive push notifications - unless you have been given special access to audio / gps functions from Apple themselves.
Short answer : Not possible. not at least with public method and want your app to be on Appstore.
For the Research purpose, you might want to try use private method and do your R&D with it. it might be possible.
I have an iOS app that automatically prints a receipt to a thermal receipt printer when an order comes in and works great. However, if the app is in the background, it does not print. Is it possible to allow it to print while running in the background?
There are only a few occasions you are allowed to run certain tasks in the background. See the Apple documentation: https://developer.apple.com/library/ios/documentation/iphone/conceptual/iphoneosprogrammingguide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html#//apple_ref/doc/uid/TP40007072-CH4-SW20
For example: playing audio, fetching the user location, sending notification or certain data from network in the background is allowed. Running your own logic during a background service is, as far as I understood, not allowed (like running it one hour after your app is gone to sleep/background mode).
The only thing that is perhaps an option, is to utilize the time your app has to finish an task after the home button is pressed. There is a timelimit however of 10 or 15 minutes.
I don't know if this is suitable for your situation?
See this stackoverflow question: iOS application executing tasks in background
And this particular piece of code to run the task in the background: https://stackoverflow.com/a/11809211/2740112
Another option is to use Guided Access, which is introduced since iOS6.
With it, you can prevent exiting the app. It's only usefull when using only the app on the device that needs to be used.
Information below from http://www.assistiveware.com/support/faq/page/136:
To turn on Guided Access, do the following:
Go to the Settings app on your device's home screen.
Tap General.
Tap Accessibility.
Under the Learning section (scroll down if necessary), tap Guided Access.
Toggle Guided Access to ON.
Tap Set Passcode and enter a four digit passcode. You will be prompted to enter it again.
(Optional) Toggle Enable Screen Sleep to ON if you want to be able to put your device to sleep with the Power button, otherwise the Power button will be disabled.
To start Guided Access for an app and prevent it from being exited, do the following:
Open the app that you want to lock in.
Quickly press your device's Home button three times to bring up the Guided Access menu.
Tap the Start button in the top right corner of the screen to activate Guided Access. A message stating "Guided Access Started" will briefly appear.
To end Guided Access for an app so it can be exited, do the following:
Quickly press your device's Home button three times to bring up the Guided Access menu.
Enter your four digit passcode when prompted.
Tap the End button in the top left corner of the screen to end Guided Access. A message stating "Guided Access Ended" will briefly appear.
Here's the knowledgebase article of Apple: http://support.apple.com/kb/ht5509
I would like to execute some code when user presses one of home, power or volume buttons(it doesn't matter, which of these).
I would like to catch events even application is minimized to background and device is sleeping.
So primary task is processing events, when device is inside user's pocket and the user presses button, but not takes out the device.
Is that possible? If it isnt't possible for power button, may be it's possible for volume or home buttons? How can I do it?
Your application cannot interact with the hardware buttons on an iOS device. Your application can receive notification that it has entered the background (which may be a side-effect of the use pressing the home button, for example) but that is about all
There is idea about volume buttons, if you create player instance you can get notifications about volume change, not sure that is still work but you can try.
see answers here: program access to iPhone volume buttons
I need a way for my app to know if the home button is pressed, while the app is running in the background. If the home button is pressed, something is gonna be added to a list inside the app. Is that possible somehow?
If your app is in the background, your app wont receive any updates. Furthermore, there isn't any way to hook into the home button click even if your app is in the foreground.
Perhaps there is a private api way to handle this, but your app certainly won't be able to both achieve this goal and be in the Apple App Store. Sorry!
In case you wanted some idea why Apple doesn't allow this, it's because they don't want the home button switch's default behavior to be altered. See this:
10.5 Apps that alter the functions of standard switches, such as the Volume Up/Down and Ring/Silent switches, will be rejected