Detect which app has been launched in android

Question

How to detect which app has been launched by user in my app i.e my application should get notified when Whatsapp is launched by user even if my app is not running in foreground

Answer 1

Depending on the Android version running your application, you will have to use different methods. On Pre-Lollipop devices, it is pretty straight-forward:

String[] result = new String[2];

List runningTasks;
ComponentName componentInfo;

runningTasks = activityManager.getRunningTasks(1);
componentInfo = runningTasks.get(0).topActivity;
result[0] = componentInfo.getPackageName();
result[1] = componentInfo.getClassName();

If you are on a Lollipop or newer device, you have to use UsageStatsManager class, which requires your application to be granted specific permissions

//no inspection ResourceType
UsageStatsManager mUsageStatsManager = (UsageStatsManager)context.getSystemService("usagestats");
long time = System.currentTimeMillis();

// We get usage stats for the last 10 seconds
List stats = mUsageStatsManager.queryUsageStats(UsageStatsManager.INTERVAL_DAILY, time - 1000*10, time);

// Sort the stats by the last time used
if(stats != null) {
    SortedMap mySortedMap = new TreeMap<>();
    for (UsageStats usageStats : stats) {
        mySortedMap.put(usageStats.getLastTimeUsed(),usageStats);
    }
    if(mySortedMap != null && !mySortedMap.isEmpty()) {
        return mySortedMap.get(mySortedMap.lastKey()).getPackageName();
    }
}

return null;

This will tell you if your apps has been granted permissions:

try {
    PackageManager packageManager = context.getPackageManager();
    ApplicationInfo applicationInfo = packageManager.getApplicationInfo(context.getPackageName(), 0);
    AppOpsManager appOpsManager = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
    int mode = appOpsManager.checkOpNoThrow(AppOpsManager.OPSTR_GET_USAGE_STATS, applicationInfo.uid, applicationInfo.packageName);
    return (mode != AppOpsManager.MODE_ALLOWED);
} catch (PackageManager.NameNotFoundException e) {
    return false;
}

And finally this will launch the Android permission granting activity for the user:

Intent intent = new Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS);
activity.startActivity(intent);

Hope that helps