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开发者_如何学运维 could not launch Activity, how can I get context of current running Activity in service class?

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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

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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

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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.

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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!

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

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

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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);

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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

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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();

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SYSTEM_ALERT_WINDOW.requrid permission in manifest and enable from from mobile seting manully its works from android 10+.

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Xiaomi Redmi 4A, Android 7, MIUI 10.2.3. Main activity for app in debug version could not start to foreground from service. There was MIUILOG- Permission Denied Activity error in logcat. Rebuilding this app in release version fixed the problem.