Android ViewPager not Showing

I am trying to make a little app to try out some things for a bigger app I am developing. I want to add a viewpager that displays four images, I developed this viewpager alone and it worked, but when I tried to add it to my other app (with just a couple of buttons) with the tag, it does not show anything and I am really stuck in here. Is possible to add the Viewpager this way? Honestly I don't have that much experience in Java, I usually program only C and Assembler and I will be reaaally glad if you could help me.

This is the xml file with the button and the include:

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
android:weightSum="1">

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Calculo Rapido"
    android:id="@+id/btcr"
    android:layout_gravity="center_vertical"
    android:layout_weight="0.16"
    android:layout_alignParentStart="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Calculo Avanzado"
    android:id="@+id/button"
    android:layout_centerVertical="true"
    android:layout_below="@+id/btcr" />

<include layout="@layout/viewpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_centerHorizontal="true"
    android:translationZ="15dp" />

Now, the MainActivity, which holds the button activity because I kept the Viewpager inside an Activity that's linked with the viewpager original layout

Button siguiente;

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

    siguiente = (Button)findViewById(R.id.btcr);
    siguiente.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent siguiente = new Intent(MainActivity.this, Main2Activity.class);
            startActivity(siguiente);
        }
    });
}

And lastly, the code for the mainpager main activity, this uses a CustomPagerAdapter saved in another java class. As I told before, this viewpager does work alone, but when I try to implement it here, with the /include tag, it doesn't show anything.

public class MainActivity extends Activity {

CustomPagerAdapter mCustomPagerAdapter;
ViewPager mViewPager;
private static int currentPage = 0;
private static int NUM_PAGES = 0;
Button siguiente;

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

    // == Setting up the ViewPager ==

    mCustomPagerAdapter = new CustomPagerAdapter(this);

    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mCustomPagerAdapter);

    final Handler handler = new Handler();
    final Runnable Update = new Runnable() {
        public void run() {
            if (currentPage == NUM_PAGES) {
                currentPage = 0;
            }
            mViewPager.setCurrentItem(currentPage++);

            if (currentPage == 5) {
                currentPage = 0;
                mViewPager.setCurrentItem(currentPage++, false);
            }
        }
    };
    Timer swipeTimer = new Timer();
    swipeTimer.schedule(new TimerTask() {
        @Override
        public void run() {
            handler.post(Update);
        }
    }, 2000, 2000);

}

Sorry if it is too long guys, but I am a little frustrated, I have tried a lot of things but it isn't working yet. Either the buttons do their thing and the ViewPager doesn't work or the ViewPager works but the buttons are dead.

I will reaaally aprecciate your help :)

Turns out, what I needed was just the simple solution. I had to put the viewpager on my activity's layout file as another object, just configuring its size and position. And then, on my onCreate I pasted the code of my functioning ViewPager. Quite simple, without requiring another layouts :)