Disable screenshots in React Native

I know that you can not 100% stop the user from taking a screenshot if he insists to. But I read that you can still stop manual screenshots by setting LayoutParams.FLAG_SECURE in Java.

I tried adding it to my MainApplication file but getWindow() kept on throwing errors no matter what I do. So I moved that line of code to the MainActivity file and it worked without any errors.

Problem is, I can still normally take screenshots.

MainApplication:

package com.testapp;
import android.app.Activity;

import com.reactnativenavigation.NavigationApplication;
import com.facebook.react.modules.i18nmanager.I18nUtil;

import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactPackage;
import com.facebook.react.shell.MainReactPackage;
import com.facebook.soloader.SoLoader;
import android.support.annotation.Nullable;

/* custom modules */
import com.oblador.vectoricons.VectorIconsPackage;
import org.pgsqlite.SQLitePluginPackage;
import com.learnium.RNDeviceInfo.RNDeviceInfo;

import java.util.Arrays;
import java.util.List;

public class MainApplication extends NavigationApplication {
  @Override
  public boolean isDebug() {
    return BuildConfig.DEBUG;
  }

  @Nullable
  @Override
  public List<ReactPackage> createAdditionalReactPackages() {
    return Arrays.<ReactPackage>asList(
        new SQLitePluginPackage(),
        new VectorIconsPackage(),
        new RNDeviceInfo()
    );
  }

  @Override
  public void onCreate() {
    super.onCreate();
    I18nUtil sharedI18nUtilInstance = I18nUtil.getInstance();
    sharedI18nUtilInstance.allowRTL(getApplicationContext(), false);
  }
}

MainActivity:

package com.testapp;
import android.widget.ImageView;
import com.reactnativenavigation.controllers.SplashActivity;
import android.os.Bundle;
import android.view.WindowManager.LayoutParams;

public class MainActivity extends SplashActivity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getWindow().setFlags(LayoutParams.FLAG_SECURE, LayoutParams.FLAG_SECURE);
  }
}