iPhone: Detecting user inactivity/idle time since last screen touch

Mike_McMaster_544 0
Viewed 75031

Has anybody implemented a feature where if the user has not touched the screen for a certain time period, you take a certain action? I'm trying to figure out the best way to do that.

There's this somewhat-related method in UIApplication:

[UIApplication sharedApplication].idleTimerDisabled;

It'd be nice if you instead had something like this:

NSTimeInterval timeElapsed = [UIApplication sharedApplication].idleTimeElapsed;

Then I could set up a timer and periodically check this value, and take some action when it exceeds a threshold.

Hopefully that explains what I'm looking for. Has anyone tackled this issue already, or have any thoughts on how you would do it? Thanks.

idle-timer objective-c iphone ios
10 Answers

Here's the answer I had been looking for:

Have your application delegate subclass UIApplication. In the implementation file, override the sendEvent: method like so:

- (void)sendEvent:(UIEvent *)event {
    [super sendEvent:event];

    // Only want to reset the timer on a Began touch or an Ended touch, to reduce the number of timer resets.
    NSSet *allTouches = [event allTouches];
    if ([allTouches count] > 0) {
        // allTouches count only ever seems to be 1, so anyObject works here.
        UITouchPhase phase = ((UITouch *)[allTouches anyObject]).phase;
        if (phase == UITouchPhaseBegan || phase == UITouchPhaseEnded)
            [self resetIdleTimer];
    }
}

- (void)resetIdleTimer {
    if (idleTimer) {
        [idleTimer invalidate];
        [idleTimer release];
    }

    idleTimer = [[NSTimer scheduledTimerWithTimeInterval:maxIdleTime target:self selector:@selector(idleTimerExceeded) userInfo:nil repeats:NO] retain];
}

- (void)idleTimerExceeded {
    NSLog(@"idle time exceeded");
}

where maxIdleTime and idleTimer are instance variables.

In order for this to work, you also need to modify your main.m to tell UIApplicationMain to use your delegate class (in this example, AppDelegate) as the principal class:

int retVal = UIApplicationMain(argc, argv, @"AppDelegate", @"AppDelegate");
Mike_McMaster_5440

Ultimately you need to define what you consider to be idle - is idle the result of the user not touching the screen or is it the state of the system if no computing resources are being used? It is possible, in many applications, for the user to be doing something even if not actively interacting with the device through the touch screen. While the user is probably familiar with the concept of the device going to sleep and the notice that it will happen via screen dimming, it is not necessarily the case that they'll expect something to happen if they are idle - you need to be careful about what you would do. But going back to the original statement - if you consider the 1st case to be your definition, there is no really easy way to do this. You'd need to receive each touch event, passing it along on the responder chain as needed while noting the time it was received. That will give you some basis for making the idle calculation. If you consider the second case to be your definition, you can play with an NSPostWhenIdle notification to try and perform your logic at that time.

wisequark_331590

Outside is 2021 and I would like share my approach to handle this without extending the UIApplication. I will not describe how to create a timer and reset it. But rather how to catch all events. So your AppDelegate starts with this:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

So all you need to do is to subclass UIWindow and override sendEvent, like below

import UIKit

class MyWindow: UIWindow {

    override func sendEvent(_ event: UIEvent){
        super.sendEvent(event)
        NSLog("Application received an event. Do whatever you want")
    }
}

And later create window with our class:

self.window = MyWindow(frame: UIScreen.main.bounds)
user_47300400
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