In my app, I want to send a Local Push notification every 30 minutes. One way is to just configure local push notification and fire it. However there is a possibility that user can change his time and move forward 30 minutes. In this way a cheat can be done.
I want to configure my app so that notification only occur after 30 minutes. How can I do that. My app does communicate with server and can get its timestamp but I want to do things which don't use much server resources.
The only way I can think of to detect a user altering the system clock is as follows:
When app launches, ask your server the time and note the difference between that and [NSDate date]. Persist that as [NSNumber numberWithFloat:serverOffset];
Implement a method like - (BOOL)deviceClockChanged that asks the server again and compares to the persisted value. If the difference is greater than some small tolerance for clock drift + latency on the synch request, then you can conclude that the clock was changed. Do all this in UTC so it works independent of user travels between time zones.
Consider this: if the user wants badly enough to fool your app about the time in order to delay a notification, messing up the rest of his phone, maybe you ought to just let him edit the notification schedule.
I can supply code examples for points 1 and 2 if you want, and if you want I can supply some #"alert text" for point 3 that will make the user feel really guilty about editing his notifications.
My original answer here. If you choose to let user edit notifications, these methods will be key... UIApplication has a property:
NSArray *scheduledLocalNotifications;
and implements:
- (void)cancelLocalNotification:(UILocalNotification *)notification
So to change one, cancel it, then reschedule it.
Related
I'm trying to set local notification in swift firing once at a definite date, but it seems there is no such option for repeat interval . By the default it triggers every 24 hours. Is there any way to submit a notification, which fires only once, so that user didn't have to even open the app or etc?
You have to set the repeatInterval of your UILocalNotification to 0:
If you assign a calendar unit such as weekly (NSCalendarUnitWeekOfYear) or yearly (NSCalendarUnitYear), the system reschedules the notification for delivery at the specified interval. Note that intervals of less than one minute are not supported.
The default value is 0, which means that the system fires the notification once and then discards it.
Regarding your second question: no! The user has to open the app at least once! Otherwise the app does not execute any of its code. Register the notification on first launch.
Problem: I know about the method applicationSignificantTimeChange to detect manual time change. But the method documentation says:
Examples of significant time changes include the arrival of midnight, an update of the time by a carrier, and the change to daylight savings time. The delegate can implement this method to adjust any object of the application that displays time or is sensitive to time changes.
So it detects not only a manual time change, but arrival of midnight as well. In my application, that will create a problem as the user will see an alertbox:
You have change the time. Please revert back to actual time.
even when he resumes the app after midnight (or may be he minimized the app and went to sleep. Next day he wakes up, resumes the app and surprisingly gets the time change notification).
Question:
How to show the alert only on manual time change and not on arrival of midnight ?
Just use NSSystemClockDidChangeNotification
Apple doc link
I have used a variant of the remote server time check for one or a few years now. It works pretty well, on iOS.
Fetch remote time.
In your time checking class, store the offset between remote time and device time, store that in a simple NSTimeInterval variable.
Now you can get "real time" at any time from your time checking class, because it can take the current device time and just add the stored offset and you will have the real time, all the time.
Whenever the app backgrounds, you will need to delete the stored offset, because the user can be fiddling with the time settings.
For every app foreground event, you will have to perform 3. again. Go get remote time again. Deny any calls to get real time until you have that offset again. Any calls depending on the real time existing will have to fail gracefully in those events where real time has not yet been fetched.
Now the offset you get should/can be compared with the offset you got last time. Decide a threshold, like 15 seconds. If the offset change from last time exceeds that threshold, the user likely changed time manually. This is a useful event for me. Of course even though the user can change the device time I will always have real time handy (most of the time).
Afaik, I always work with UTC time stamps to avoid any locale troubles.
Always its better to check such things with server time.
Follow below steps.
Fetch the server time and convert to current locale.
Check mobile time using current locale.
If they are not same, that means user has changed the time.
Let me know if this is clear or not.
I'm currently working on a new game for iOS using Cocos2D. The game needs to advance states after x amount of time since the first launch. So for example:
State - Time
initial launch
24hrs
48hrs
My first idea was to just get the data and time on first launch and save it to a file. Then I could check it ever now and again to see how much time has passed. The problem with this is I need it to be in realtime so that the changes will take effect immediately once the state is reached. It also needs to continue when the user is not using the app. The functionality I'm looking for is kind of similar to how the iOS strategy games work where you build structures that take x amount of time.
Anyway my question(s) is; is there some sort of library that can accomplish this and how can I get it to continue after the user exits the app?
It can't. There is - apart from kind of misusing video/music playing etc. no way for your app to do work while it is not running.
You have two things you can do to simulate that behavior (and I suppose the strategy games do this, too):
You can calculate at any time while a user is still running your app the points in the future when something should happen (eg a housing structure is finished). When the user leave your app, store these future times as local events - then the user will get notified that something has happened in your game (eg message "The church has been built. Do you want to go to church now?)". Pressing yes will open your app, and you can do whatever is necessary to indeed build the church. So in fact you don't do it at the time when it occurred, but when the user opens your app the next time.
Like 1, but without notification. Just remember when the user leaves the app (eg in your settings, I would use a property list; set it when the app delegate gets the appWillResignActive event), and the next time he starts do whatever would have been done in the meantime - he won't be able to tell the difference :-).
It's all about make believe here :-).
Let's say, Tiny Tower. On this iPhone game, you can have shops in your tower. You can suspend or turn off the iPhone, but when you return to the game, you will be reported about the shop winnings during your time away.
There are also push notifications when a building is complete etc.
I fear I do not understand how that works, exactly. I'm not asking for the exact solution, I just need to know where to begin researching. One idea I had some time ago was like calculate the amount of seconds the user was away (current time minus the time when you left) and then calculate shop processing for every one of these seconds. But I'm not sure of that.
A better way would be to calculate before you close the app.
Figure out what time it is, then calculate when in the future certain tasks will be completed. This way, you can schedule push notifications to the server ahead of time.
If you calculate after you have re-opened the app, and you can't run processes with the app closed, how will it know when to push?
Take a look at this article about push notifications to understand a little bit better how they work.
http://blog.boxedice.com/2009/07/10/how-to-build-an-apple-push-notification-provider-server-tutorial/
For offline games you add temporal logic to your items and recalculate when game is launched. For online games you retrieve game state from the server, which is constantly recalculating for all users, even disconnected ones.
Game most probably does not actually process in the background (most apps are not allowed to do anything while in background). When you relaunch the game, it calculates how much time has passed, and then processes all the events that would have happened in the meantime.
Additionally, as Paul.s mentioned in comments below, as well as other people in other answers have suggested, on iOS4 you can use local push notifications scheduled before close.
It is either server side execution of the game or if it is a game of chance or something like Farmville where it's determined by time duration.
If you were to make a server and/or game like this then you would need to decide which route to take.
If it will be something where the user has good days and sometimes bad days then you'll need a lot more server power. however, if it's something like time based then you would be able to tell the last time they were logged in and the next time that they should be awarded. you can also take this idea and for each variable that you store, you store how long it takes to be complete and the start time. Then you would do a simple If then o see if the item is ready. The same thing can work for a number of visitors. Where you have 10 visitors per item per hour. If you have two items then each hour you will receive 20 visitors.
i want to send a notification each day at the same time with different information. I got no problem with showing the alert when i want to. The problem is what to show. First i tried to schedule one alert every day with different information in them, but that seems really inefficient. Then i tried with
-(void)application(UIApplication*)app didReceiveLocalNotification:(UILocalNotification *)Notif{}
but found out that it runs when the application is running in foreground only.
Is there any way to provide an array or something like it with the alert and tell the alert to get its body from the array with different index for different days?
Or should i do it with some notification that can run when the app is in background mode and the alert show and make a new alert?
All information must be provided when you schedule a local notification, so no, a notification's body cannot be sourced from an array as you described. If users are likely to open your app often and you know notification content in advance, perhaps you could ensure that x notifications are always scheduled (could be achieved by inspecting UIApplication's scheduledLocalNotifications).
This solution isn't ideal though, as it relies on users opening your app on a (somewhat) regular basis. I think push notifications are probably your best bet, but that requires access to a server, etc.
Yeah push could prob be the solution. But i dont have a server for that. The users will most likeley not open it any more after they have opened it the first time to activite the local-messages. So then this isnt really possible to do without push. when i tried a for-loop to schedule 250 days with different text each day it took about 2 minutes on iphone 4 so its not duable.