title: Null pointer Exception on TabLayout
body: <pre><code>Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.TabLayout.addOnTabSelectedListener(android.support.design.widget.TabLayout$OnTabSelectedListener)' on a null object reference
  </code></pre>
  
  <p>Declared this before onCreate():</p>
  
  <pre><code>TabLayout.OnTabSelectedListener listener;
  </code></pre>
  
  <p>and this in onCreate():</p>
  
  <pre><code>TabLayout tabLayout = (TabLayout) findViewById(R.id.tabLayout);
  listener = new TabLayout.OnTabSelectedListener(){
          @Override
          public void onTabSelected(TabLayout.Tab tab) {
              viewPager.setCurrentItem(tab.getPosition());
          }
  
          @Override
          public void onTabUnselected(TabLayout.Tab tab) {
  
          }
  
          @Override
          public void onTabReselected(TabLayout.Tab tab) {
  
          }
      };
      tabLayout.addOnTabSelectedListener(listener);
  </code></pre>
  
  <p>I'm having trouble seeing how listener is null. I have other NullPointerExceptions that even claim null object on primitives including ints defined by drawable pngs?</p>