CODEWITHSUNDEEP
androidandroid-activity
Ion Aalbers
Ion Aalbers

Reputation: 8030

Android: How do I avoid starting activity which is already in stack?

Lets try to explain my question: I got an application and a service. The application is started with activity A. The service sends a broadcast that will let the application start Activity B Now the user starts activity C.

Now the service wants to start activity B again. But how do I let him know that the activity is still on the stack, or is there an intent flag for this?

How do I avoid that it will launch activity B because its already in the stack?

Upvotes: 57

Views: 54508

Answers (7)

Gal Rom
Gal Rom

Reputation: 6461

You may consider using android:launchMode="singleTop" instead of android:launchMode="singleInstance" Good article about the differences

Upvotes: 4

Jitesh Mohite
Jitesh Mohite

Reputation: 34170

I would suggest you use Intent.FLAG_ACTIVITY_CLEAR_TOP as it will remove all activities which start on top of your targeted activity.

eg :

Intent intent = new Intent(sourceActivity, Target activity);

intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

startActivity(intent)

Upvotes: -1

Andrew
Andrew

Reputation: 37969

Approaches android:launchMode="singleInstance" and just adding flags to the Intent do not work for me. What works is that:

In the code where activity gets started:

Intent intent = new Intent(activity, ActivityThatHasToBeStarted.class);
intent.setFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
startActivity(intent);

In the ActivityThatHasToBeStarted:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if ((getIntent().getFlags() & Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT) != 0) {
        finish();
        return;
    }
    // Code for this creation
}

Upvotes: 7

Alex
Alex

Reputation: 1644

If you don't need the second activity anymore, it is good practise to finish it, then you should do this on the second activity after the operation is ended:

startActivity(new Intent(this, FirstActivity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
finish();

Upvotes: 2

Pellet
Pellet

Reputation: 2437

If the activity will be on the top if already started, set the FLAG_ACTIVITY_SINGLE_TOP flag

intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
mContext.startActivity(intent);

Upvotes: 11

MKJParekh
MKJParekh

Reputation: 34291

I think you need to make your activity B singleInstance that if it's already create you don't want to create again, that is launch mode of the activity can be defined in manifest android:launchMode that defines how the activity will be instanciated.

in your case use android:launchMode="singleInstance"

Upvotes: 82

Sadeshkumar Periyasamy
Sadeshkumar Periyasamy

Reputation: 4908

You can use flag Intent.FLAG_ACTIVITY_NEW_TASK. If the activity is already running it will bring that to front instead of creating new activity.

If you add Intent.FLAG_ACTIVITY_CLEAR_TOP with this, then all the activities after this activity in the backstack will be cleared.

Upvotes: 31

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