Start Activity from Service in Android

Android:

public class LocationService extends Service {

    @Override
	public void onStart(Intent intent, int startId) {
		super.onStart(intent, startId);
		startActivity(new Intent(this, activity.class));
	}
}

I launched this service from Activity

In Activity if condition satisfies start

startService(new Intent(WozzonActivity.this, LocationService.class));

from my LocationService mentioned above could not launch Activity, how can I get context of current running Activity in service class?

From inside the Service class:

Intent dialogIntent = new Intent(this, MyActivity.class);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(dialogIntent);

But, this does not work from Android 10+ due to battery optimisation restrictions

I had the same problem, and want to let you know that none of the above worked for me. What worked for me was:

 Intent dialogIntent = new Intent(this, myActivity.class);
 dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 this.startActivity(dialogIntent);

and in one my subclasses, stored in a separate file I had to:

public static Service myService;

myService = this;

new SubService(myService);

Intent dialogIntent = new Intent(myService, myActivity.class);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
myService.startActivity(dialogIntent);

All the other answers gave me a nullpointerexception.

UPDATE ANDROID 10 AND HIGHER

Start an activity from service (foreground or background) is no longer allowed.

There are still some restrictions that can be seen in the documentation

https://developer.android.com/guide/components/activities/background-starts

Another thing worth mentioning: while the answer above works just fine when our task is in the background, the only way I could make it work if our task (made of service + some activities) was in the foreground (i.e. one of our activities visible to user) was like this:

	Intent intent = new Intent(storedActivity, MyActivity.class);
	intent.setAction(Intent.ACTION_VIEW);
	intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
	intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
	storedActivity.startActivity(intent);

I do not know whether ACTION_VIEW or FLAG_ACTIVITY_NEW_TASK are of any actual use here. The key to succeeding was

storedActivity.startActivity(intent);

and of course FLAG_ACTIVITY_REORDER_TO_FRONT for not instantiating the activity again. Best of luck!

one cannot use the Context of the Service; was able to get the (package) Context alike:

Intent intent = new Intent(getApplicationContext(), SomeActivity.class);

Alternately,

You can use your own Application class and call from wherever you needs (especially non-activities).

public class App extends Application {
	
	protected static Context context = null;

	@Override
	public void onCreate() {
		super.onCreate();
		context = getApplicationContext();
	}

	public static Context getContext() {
		return context;
	}
	
}

And register your Application class :

<application android:name="yourpackage.App" ...

Then call :

App.getContext();

You can also use getApplicationContext() method in your Service to run the startActivity() method as written below:

Intent myIntent = new Intent();
myIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
getApplicationContext().startActivity(myIntent);

If you need to recal an Activity that is in bacgrounde, from your service, I suggest the following link. Intent.FLAG_ACTIVITY_NEW_TASK is not the solution.

https://stackoverflow.com/a/8759867/1127429