Hi guys i have an app which is almost totally complete.It is a music player.It plays music from a service.
When i press back button that activity which started the service is obviously destroyed.(i want the activity to be destroyed so that the user can navigate other activities.The reason i am telling this is because singleton|singleinstance etc won't solve my problem) But i don't know how i can recreate the activity from the notification.
Also when the activity which started the service is visible(and not destroyed) then too if i click on the notification, my app stops unexpectedly.And hence i have two problems to solve here.
I am using a global variable which is a list and hence i don't think i need to save data before destruction.I think i know the concept how the activity state can be restored and recreated but i think i am not totally aware how it can be done.I am not sure in which method the activity state should be restored and how can it be restored ??Also i am starting the service in onCreate method.Should i change it to some other method?Can starting the service in onCreate be a problem when restoring the activity ?
Extra Note :Global Variables are available throughout the application and are independent of an individual activity,as they extend Application.Also Bundle will only help when the activity is destroyed by the system.When Pressing the back button we explicitly destroy the activity and hence data cannot be saved into the bundle as onSaveInstanceState is never called by the activity.
If the data is consistent and reflects with the Service, then you need to bind to the Service and get the data from the IBinder (which can wrap a Service object). I, personally, prefer this method because I simply don't like overriding the Application.
An alternate method is to save data via the SharedPreferences. Save it your Activity state in onPause() and restore in onCreate(). Assuming you're not saving hundreds of items, it is very low overhead. This should only be used for data that reflects the state of the Activity itself.
You can play and stop your player based on Activity life cycle like
OnPause -you should call player.stop()
onresume you should call play and
ondestroy you need to release your player instance.
call a thread inside your service to get data from server so that it will work smoothly.
you should release mediaplayer instances by calling release or reset .
You can use Pending intent in notification so when you will see notification then you can open your activity whatever mentioned in pending intent.
Activity state should be restored in onCreate. The onCreate method gets a Bundle as parameter which contains key-value pairs of data. If this parameter is null, it means that no previous state was saved. Just check if it's not null, and restore things if necessary:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(...);
...
if(savedInstanceState!=null) {
// Restore activity state based on saved data!
}
}
Of course you need to save data if you want to use it at restoration. System automatically calls the activity's onSaveInstance state method in which you can put data into the bundle.
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putInt("key", value); // Store data
}
Please note that this all applies to the case when system destroys your application automatically. (For example, when other apps in the foreground run out of memory.) This mechanism is to get your activity back to a state in which the user last saw it.
