title: Why am I getting this error? Please see the details
body: <p>I'm developing a material design app &amp; for applying activity transition I have written the following code in my <code>MainActivity.java</code></p>
  
  <p>My <code>MainActivity.java</code> file's code:</p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
  
      public Toolbar toolbar;
      public TabLayout tabLayout;
      public ViewPager viewPager;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.LOLLIPOP) {
              // Call some material design APIs here
              // enable transitions
              getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
          } else {
  
          }
          setContentView(R.layout.activity_main);
  
          SpannableString s = new SpannableString("abc");
          s.setSpan(new TypefaceSpan(this, "Pacifico.ttf"), 0, s.length(),
                  Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
  
          toolbar = (Toolbar) findViewById(R.id.toolbar);
          setSupportActionBar(toolbar);
  
          getSupportActionBar().setDisplayHomeAsUpEnabled(false);
          getSupportActionBar().setTitle(s);
  
          viewPager = (ViewPager) findViewById(R.id.viewpager);
          setupViewPager(viewPager);
  
          tabLayout = (TabLayout) findViewById(R.id.tabs);
          tabLayout.setupWithViewPager(viewPager);
          customTabFont();
  
      }
  
      private void customTabFont() {
  
          String fontPath = "fonts/Pacifico.ttf";
  
          Typeface tf = Typeface.createFromAsset(getAssets(), fontPath);
  
          TextView tabOne = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
          tabOne.setText("Accept a Request");
          tabOne.setTypeface(tf);
          tabLayout.getTabAt(0).setCustomView(tabOne);
  
          TextView tabTwo = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
          tabTwo.setText("Post a Request");
          tabTwo.setTypeface(tf);
          tabLayout.getTabAt(1).setCustomView(tabTwo);
  
      }
  
      private void setupViewPager(ViewPager viewPager) {
          ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
          adapter.addFragment(new AcceptARequest(), "Accept a Request");
          adapter.addFragment(new PostARequest(), "Post a Request");
          viewPager.setAdapter(adapter);
      }
  
      class ViewPagerAdapter extends FragmentPagerAdapter {
          private final List&lt;Fragment&gt; mFragmentList = new ArrayList&lt;&gt;();
          private final List&lt;String&gt; mFragmentTitleList = new ArrayList&lt;&gt;();
  
          public ViewPagerAdapter(FragmentManager manager) {
              super(manager);
          }
  
          @Override
          public Fragment getItem(int position) {
              return mFragmentList.get(position);
          }
  
          @Override
          public int getCount() {
              return mFragmentList.size();
          }
  
          public void addFragment(Fragment fragment, String title) {
              mFragmentList.add(fragment);
              mFragmentTitleList.add(title);
          }
  
          @Override
          public CharSequence getPageTitle(int position) {
              return mFragmentTitleList.get(position);
          }
      }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.menu_main, menu);
          return true;
      }
  
      @Override
      public boolean onOptionsItemSelected(MenuItem item) {
          // Handle action bar item clicks here. The action bar will
          // automatically handle clicks on the Home/Up button, so long
          // as you specify a parent activity in AndroidManifest.xml.
          int id = item.getItemId();
  
          //noinspection SimplifiableIfStatement
          if (id == R.id.action_profile) {
              // Check if we're running on Android 5.0 or higher
              if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.LOLLIPOP) {
                  // Call some material design APIs here
                  getWindow().setExitTransition(new Explode());
                  Intent profileIntent = new Intent(MainActivity.this, ProfileActivity.class);
                  startActivity(profileIntent, ActivityOptions
                          .makeSceneTransitionAnimation(this).toBundle());
              } else {
                  // Implement this feature without material design
                  Intent profileIntent = new Intent(MainActivity.this, ProfileActivity.class);
                  startActivity(profileIntent);
              }
          } else if (id == R.id.action_settings) {
              Intent settingsIntent = new Intent(MainActivity.this, SettingsActivity.class);
              startActivity(settingsIntent);
          } else if (id == R.id.action_help) {
              Intent helpIntent = new Intent(Intent.ACTION_SEND);
              Intent chooser = Intent.createChooser(helpIntent, "Choose an app");
              helpIntent.putExtra(Intent.EXTRA_EMAIL, new String[]{"help@abcxyz123.com"});
              helpIntent.setType("message/rfc822");
              startActivity(chooser);
          } else if (id == R.id.action_faqs) {
              Intent faqsIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.abcxyz123.com/faqs"));
              startActivity(faqsIntent);
          } else if (id == R.id.action_about) {
              Intent aboutIntent = new Intent(MainActivity.this, AboutActivity.class);
              startActivity(aboutIntent);
          }
  
          return super.onOptionsItemSelected(item);
      }
  }
  </code></pre>
  
  <p>After running the app, I'm getting following error: </p>
  
  <pre><code>android.util.AndroidRuntimeException: requestFeature() must be called before adding content must be called before adding content.
  </code></pre>
  
  <p>I do not understand why am I getting this error when I have added the <code>requestFeature()</code> before adding the content?</p>
  
  <p>Please let me know.</p>
  
  <p>I'm new to StackOverflow, so please cooperate.</p>
  
  <p>Thanks in advance.</p>