CODEWITHSUNDEEP
android
alex_c
alex_c

Reputation: 2046

How to run callback on application launch?

I know Android's Activity model is a bit different from what I usually consider to be an "app".

I want to do something (in this case, check some notifications on a server and show them if available) when my app is "launched". What is a good way to accomplish this?

I likely don't want to do it in an activity's OnCreate, since each activity can be created any number of times - the code would get called more often than necessary.

The app also has multiple entry points - would I have to duplicate the check in each activity?

What I'm thinking of doing is setting up this code inside the Application object, along with a flag that tracks whether it's already been called - and just call it from each Activity's onCreate().

Is there a better or more "proper" way to do this?

Upvotes: 10

Views: 3740

Answers (3)

Isaac Waller
Isaac Waller

Reputation: 32750

The right, Android-approved way to do this is:

  • Create your own android.app.Application class
  • Override the onCreate method
  • In the AndroidManifest.xml, change the android:name attribute of the application element to the name of your class
  • Now, whenever your app is "started" (any one of your activites is started for the first time and no other instances are alive) onCreate will be called.

You may also find the onTerminate method useful.

Upvotes: 12

Jarett Millard
Jarett Millard

Reputation: 5968

There's probably no harm in putting it in onCreate; the Activity is really only destroyed when the OS needs the RAM for something else, not when the user goes to another app.

EDIT: You can also have a Service that runs when the device gets booted up, too. This might be a better option if you also want to check when the app starts, since you'll only have to call context.startService from the Activity to run the check. Just be sure to stop it when it's done if you don't need it to be persistent.

Upvotes: 0

joeforker
joeforker

Reputation: 41817

Can you just check if the bundle passed to onCreate() is null?

It's not null "If the activity is being re-initialized after previously being shut down..."

Upvotes: 0

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