Can push notifications be used to run code without

问题:

I have an app which needs to communicate with a server (to refresh it's data) once every 24 hours. This needs to happen even if the app is not open, nor in the background.

Ideally what I'd like is:

• Every 24 hours, my server sends a push notification to iPad
• This wakes up the app, and runs the code necessary to refresh the data
• The notification is then discarded

Is any of this possible?
Is the app only woken up AFTER the user clicks on the notification? Or can I run some code before showing the notification? Can I even discard the notification message?

If Push notifications are not the right way to do this, what is???

Thanks guys!

回答1:

With release of iOS 7 this is finally possible using Remote/Silent notifications. They work same as Push notifications but instead of alerting the user immediately they can fire up background fetch mode and upload/download new content.

Here is simple tutorial:http://www.objc.io/issue-5/multitasking.html

回答2:

This is only possible if your application is a Newsstand App, if it is, you can send a push notification with content-available: true once every 24 hours.

If it is not a newsstand app, you can instead use GPS fences to run code. It is allowed to let the user set up GPS fences if they want the app to update when the user comes close to an area (ie. their home / work). This will wake the app and you can run the background download then. Instapaper for example does this.

回答3:

if the period is always going to be 24 hours you can use local notifications instead of push notifications.

your app won't be able to run any code unless the user open the push notification, push notifications are handled by the OS and your app have no control on them while it's not active or in the background you should take a look at the push notification programming guide

an alternative way to accomplish what you are trying to do, is to get the data from the server every time the app is started and the last update happened 24 hrs earlier ,

1. every time you contact the server save the date in NSUserDefault
2. every time the user opens the app check if the last server contact happened before 24 hours then refresh data

回答4:

It is possible using a so called VOIP Push Notification. This notification can run code in the background, even when the app is completely closed.