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.
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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?)
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.
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 came to know that iOS does't support widgets this is what i have read.But i am making application on Security in iOS, i want the user to perform some action when he is in need of help without opening the application.
I know iOS supports few background modes like play audio,receive location updates,voip etc.
Can anyone suggest me any alternative to fire some methods without opening the application like pressing some button when in dangerous situation to call those methods.
I don't know whether we can do it or not.
But have a look.
You said we can implement background modes like audio, location, voip updates etc.
Let take the example of Audio mode. It has previous, play/pause, and next button in the lockscreen.
What you can do is play an audio when the application is in background mode.
Check whether the any of the music buttons are pressed more than 3 times. If this is the case trigger alert messages for security and send them to appropriate persons or do your own action.
I don't know whether we can do this or not. Even if it is possible, I can't say Apple will allow such false actions for buttons which are meant for some purpose.
Also see whether we can get detect volume button presses when in background mode. If that is possible you can do that. Because even my LG mobile has an SOS mode which is enabled when I press volume buton in lockscreen 4 times. Apple may allow this action if it possible