Initial Setup

First and foremost, in order to fetch a list of used applications, we need to secure USAGE ACCESS permission from the user. For that, declare below line in the application's Manifest.xml

       <uses-permission
        android:name="android.permission.PACKAGE_USAGE_STATS"
        tools:ignore="ProtectedPermissions" />

& to check, if the permission is granted or not, call

          if (Monitor.hasUsagePermission())
        else
            Monitor.requestUsagePermission();

also ask for android.permission.READ_PHONE_STATE permission if data usage is required. Neglect, if data usage in not required

 if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_PHONE_STATE}, 100);
        }