initializing Google Tag Manager

SplashActivity.java

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import com.google.android.gms.common.api.PendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.tagmanager.ContainerHolder;
import com.google.android.gms.tagmanager.TagManager;

import java.util.concurrent.TimeUnit;

public class SplashActivity extends AppCompatActivity {

    private static final String TAG = SplashActivity.class.getSimpleName();

    // change this value to your container id
    private static final String CONTAINER_ID = "GTM-KXBGMH";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        // initializing Google Tag Manager
        TagManager tagManager = TagManager.getInstance(this);
        PendingResult<ContainerHolder> pending = tagManager.loadContainerPreferNonDefault(CONTAINER_ID, R.raw.gtm_default_container);
        pending.setResultCallback(new ResultCallback<ContainerHolder>() {
            @Override
            public void onResult(ContainerHolder containerHolder) {
                ContainerHolderSingleton.setContainerHolder(containerHolder);
                if (!containerHolder.getStatus().isSuccess()) {
                    Log.e(TAG, "failure loading container");
                    displayErrorToUser(R.string.load_error);
                    return;
                }
                startMainActivity();
            }
        }, 2, TimeUnit.SECONDS);
    }

    private void displayErrorToUser(int resId) {
        Snackbar.make(findViewById(R.id.root), resId, Snackbar.LENGTH_LONG);
    }

    private void startMainActivity() {
        startActivity(new Intent(getApplicationContext(), MainActivity.class));
        finish();
    }
}