Android: how do I check if activity is running?

Question

You can use a static variable within the activity.

class MyActivity extends Activity {
     static boolean active = false;

      @Override
      public void onStart() {
         super.onStart();
         active = true;
      } 

      @Override
      public void onStop() {
         super.onStop();
         active = false;
      }
}

The only gotcha is that if you use it in two activities that link to each other then onStop on the first is sometimes called after onStart in second. So both might be true briefly.

Depending on what you are trying to do (update the current activity from a service?). You could just register a static listener in the service in your activity onStart method then the correct listener will be available when your service wants to update the UI.

I realize this issue is quite old, but I think it's still worth sharing my solution as it might be useful to others.

This solution wasn't available before Android Architecture Components were released.

Activity is at least partially visible

getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.STARTED)

Activity is in the foreground

getLifecycle().getCurrentState().isAtLeast(Lifecycle.State.RESUMED)

I think more clear like that:

  public boolean isRunning(Context ctx) {
        ActivityManager activityManager = (ActivityManager) ctx.getSystemService(Context.ACTIVITY_SERVICE);
        List<RunningTaskInfo> tasks = activityManager.getRunningTasks(Integer.MAX_VALUE);

        for (RunningTaskInfo task : tasks) {
            if (ctx.getPackageName().equalsIgnoreCase(task.baseActivity.getPackageName())) 
                return true;                                  
        }

        return false;
    }

An option without using any auxiliar variable is:

activity.getWindow().getDecorView().getRootView().isShown()

where activity is f.e.: this or getActivity().

The value returned by this expression changes in onStart() / onStop(), which are the events that start / stop showing the layout of the activity on the phone.

I used MyActivity.class and getCanonicalName method and I got answer.

protected Boolean isActivityRunning(Class activityClass)
{
        ActivityManager activityManager = (ActivityManager) getBaseContext().getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> tasks = activityManager.getRunningTasks(Integer.MAX_VALUE);

        for (ActivityManager.RunningTaskInfo task : tasks) {
            if (activityClass.getCanonicalName().equalsIgnoreCase(task.baseActivity.getClassName()))
                return true;
        }

        return false;
}

Far better way than using a static variable and following OOP

Shared Preferences can be used to share variables with other activities and services from one application

    public class example extends Activity {

    @Override
    protected void onStart() {
        super.onStart();

        // Store our shared preference
        SharedPreferences sp = getSharedPreferences("OURINFO", MODE_PRIVATE);
        Editor ed = sp.edit();
        ed.putBoolean("active", true);
        ed.commit();
    }

    @Override
    protected void onStop() {
        super.onStop();

        // Store our shared preference
        SharedPreferences sp = getSharedPreferences("OURINFO", MODE_PRIVATE);
        Editor ed = sp.edit();
        ed.putBoolean("active", false);
        ed.commit();

    }
}

Use shared preferences. It has the most reliable state information, less application switch/destroy issues, saves us to ask for yet another permission and it gives us more control to decide when our activity is actually the topmost. see details here abd here also