Android: How can I get the current foreground acti

Question

Is there a native android way to get a reference to the currently running Activity from a service?

I have a service running on the background, and I would like to update my current Activity when an event occurs (in the service). Is there a easy way to do that (like the one I suggested above)?

Answer 1

Here's a good way to do it using the activity manager. You basically get the runningTasks from the activity manager. It will always return the currently active task first. From there you can get the topActivity.

Example here

There's an easy way of getting a list of running tasks from the ActivityManager service. You can request a maximum number of tasks running on the phone, and by default, the currently active task is returned first.

Once you have that you can get a ComponentName object by requesting the topActivity from your list.

Here's an example.

    ActivityManager am = (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
    List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
    Log.d("topActivity", "CURRENT Activity ::" + taskInfo.get(0).topActivity.getClassName());
    ComponentName componentInfo = taskInfo.get(0).topActivity;
    componentInfo.getPackageName();

You will need the following permission on your manifest:

<uses-permission android:name="android.permission.GET_TASKS"/>

Answer 2

Just recently found out about this. With apis as:

• minSdkVersion 19

• targetSdkVersion 26

  ActivityManager.getCurrentActivity(context)

Hope this is of any use.

Answer 3

Use ActivityManager

If you only want to know the application containing the current activity, you can do so using ActivityManager. The technique you can use depends on the version of Android:

• Pre-Lollipop: ActivityManager.getRunningTasks (example)
• Lollipop: ActivityManager.getRunningAppProcesses (example)

Benefits

• Should work in all Android versions to-date.

Disadvantages

• Doesn't work in Android M (based on testing using the pre-release emulator)
• The documentation for these APIs says they're only intended for debugging and management user interfaces.
• If you want real-time updates, you need to use polling.
• Relies on a hidden API: ActivityManager.RunningAppProcessInfo.processState
• This implementation doesn't pick up the app switcher activity.

Example (based on KNaito's code)

public class CurrentApplicationPackageRetriever {

    private final Context context;

    public CurrentApplicationPackageRetriever(Context context) {
        this.context = context;
    }

    public String[] get() {
        if (Build.VERSION.SDK_INT < 21)
            return getPreLollipop();
        else
            return getLollipop();
    }

    private String[] getPreLollipop() {
        @SuppressWarnings("deprecation")
        List<ActivityManager.RunningTaskInfo> tasks =
            activityManager().getRunningTasks(1);
        ActivityManager.RunningTaskInfo currentTask = tasks.get(0);
        ComponentName currentActivity = currentTask.topActivity;
        return new String[] { currentActivity.getPackageName() };
    }

    private String[] getLollipop() {
        final int PROCESS_STATE_TOP = 2;

        try {
            Field processStateField = ActivityManager.RunningAppProcessInfo.class.getDeclaredField("processState");

            List<ActivityManager.RunningAppProcessInfo> processes =
                activityManager().getRunningAppProcesses();
            for (ActivityManager.RunningAppProcessInfo process : processes) {
                if (
                    // Filters out most non-activity processes
                    process.importance <= ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND
                    &&
                    // Filters out processes that are just being
                    // _used_ by the process with the activity
                    process.importanceReasonCode == 0
                ) {
                    int state = processStateField.getInt(process);

                    if (state == PROCESS_STATE_TOP)
                        /*
                         If multiple candidate processes can get here,
                         it's most likely that apps are being switched.
                         The first one provided by the OS seems to be
                         the one being switched to, so we stop here.
                         */
                        return process.pkgList; 
                }
            }
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new RuntimeException(e);
        }

        return new String[] { };
    }

    private ActivityManager activityManager() {
        return (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    }

}

Manifest

Add the GET_TASKS permission to AndroidManifest.xml:

<!--suppress DeprecatedClassUsageInspection -->
<uses-permission android:name="android.permission.GET_TASKS" />

Answer 4

It can be done by:

1. Implement your own application class, register for ActivityLifecycleCallbacks - this way you can see what is going on with our app. On every on resume the callback assigns the current visible activity on the screen and on pause it removes the assignment. It uses method registerActivityLifecycleCallbacks() which was added in API 14.

   public class App extends Application {
   
   private Activity activeActivity;
   
   @Override
   public void onCreate() {
       super.onCreate();
       setupActivityListener();
   }
   
   private void setupActivityListener() {
   registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
           @Override
           public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
           }
           @Override
           public void onActivityStarted(Activity activity) {
           }
           @Override
           public void onActivityResumed(Activity activity) {
               activeActivity = activity;
           }
           @Override
           public void onActivityPaused(Activity activity) {
               activeActivity = null;
           }
           @Override
           public void onActivityStopped(Activity activity) {
           }
           @Override
           public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
           }
           @Override
           public void onActivityDestroyed(Activity activity) {
           }
       });
   }
   
   public Activity getActiveActivity(){
       return activeActivity;
   }
   
   }
   

2. In your service call getApplication() and cast it to your app class name (App in this case). Than you can call app.getActiveActivity() - that will give you a current visible Activity (or null when no activity is visible). You can get the name of the Activity by calling activeActivity.getClass().getSimpleName()

Answer 5

Use this code for API 21 or above. This works and gives better result compared to the other answers, it detects perfectly the foreground process.

if (Build.VERSION.SDK_INT >= 21) {
    String currentApp = null;
    UsageStatsManager usm = (UsageStatsManager) this.getSystemService(Context.USAGE_STATS_SERVICE);
    long time = System.currentTimeMillis();
    List<UsageStats> applist = usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY, time - 1000 * 1000, time);
    if (applist != null && applist.size() > 0) {
        SortedMap<Long, UsageStats> mySortedMap = new TreeMap<Long, UsageStats>();
        for (UsageStats usageStats : applist) {
            mySortedMap.put(usageStats.getLastTimeUsed(), usageStats);

        }
        if (mySortedMap != null && !mySortedMap.isEmpty()) {
            currentApp = mySortedMap.get(mySortedMap.lastKey()).getPackageName();
        }
    }

Answer 6

I don't know if it's a stupid answer, but resolved this problem by storing a flag in shared preferences every time I entered onCreate() of any activity, then I used the value from shered preferences to find out what it's the foreground activity.