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copied!<p>The short answer is: use bundles as it makes saving your state out when you're backgrounded easier. Also, it's complicated.</p> <p>The long answer:</p> <p>My understanding is, as soon as you Activity's onPause method is called (and onSaveInstanceState which gives you a bundle into which you should store your Activity's data) your process can be terminated without further warning. Later, when the user comes back to your application, your activity is given an onCreate call with that original bundle from which to restore its state. This will happen to all your activitys in what was your original stack. </p> <p>Being able to restore your state from the bundle (which Android will save for you as your process goes away) is how Android maintain's the myth of multi-tasking. If you don't dump your activity's state out to a bundle each time onSaveInstanceState is called, your app will look like it's been restarted when the user may have just switched out for a second. This can be especially troubling when the system is resource constrained as the system would need to kill off processes more often in order to keep the device running quickly</p> <p><strong>Why the Application can be Bad</strong></p> <p>The Application does not actually get a chance to save any of its data if the process is shut down. It does have an onDestroy method but the docs will tell you that this actually never gets called by the system on an actual device. This means that, in the constrained case I mentioned above, any incidental information about what's going on within an Activity (if you've saved it in the Application) will be lost if the process is ended.</p> <p>Developer's often miss this case (and it can be really annoying for users) because they're either running on a dev phone which never gets hit with using many applications at the same time. We're also never using the app for a while, then switching to another application and, after a while, switching back again.</p>

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