title: Android Studio Can't resolve fragmentActivity and ViewPager imports
body: <p>I follow the tutorial of developing swipe-able tabs. When I import:</p>
  
  <pre><code>import android.support.v4.app.FragmentActivity;
  import android.support.v4.view.ViewPager;
  </code></pre>
  
  <p>Android Studio shows me cannot resolve the symbol "ViewPager" and "FragmentActivity".
  How to solve this? thanks.</p>
  
  <p>Below is the entire code of my project.</p>
  
  <pre><code>import android.app.ActionBar;
  import android.app.ActionBar.Tab;
  import android.app.FragmentTransaction;
  import android.os.Bundle;
  import android.support.v4.app.FragmentActivity;
  import android.support.v4.view.ViewPager;
  
  public class MainActivity extends FragmentActivity implements
      ActionBar.TabListener {
  
  private ViewPager viewPager;
  private TabsPagerAdapter mAdapter;
  private ActionBar actionBar;
  // Tab titles
  private String[] tabs = { "Top Rated", "Games", "Movies" };
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
      // Initilization
      viewPager = (ViewPager) findViewById(R.id.pager);
      actionBar = getActionBar();
      mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
  
      viewPager.setAdapter(mAdapter);
      actionBar.setHomeButtonEnabled(false);
      actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
  
      // Adding Tabs
      for (String tab_name : tabs) {
          actionBar.addTab(actionBar.newTab().setText(tab_name)
                  .setTabListener(this));
      }
  
      /**
       * on swiping the viewpager make respective tab selected
       * */
      viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
  
          @Override
          public void onPageSelected(int position) {
              // on changing the page
              // make respected tab selected
              actionBar.setSelectedNavigationItem(position);
          }
  
          @Override
          public void onPageScrolled(int arg0, float arg1, int arg2) {
          }
  
          @Override
          public void onPageScrollStateChanged(int arg0) {
          }
      });
  }
  
  @Override
  public void onTabReselected(Tab tab, FragmentTransaction ft) {
  }
  
  @Override
  public void onTabSelected(Tab tab, FragmentTransaction ft) {
      // on tab selected
      // show respected fragment view
      viewPager.setCurrentItem(tab.getPosition());
  }
  
  @Override
  public void onTabUnselected(Tab tab, FragmentTransaction ft) {
  }
  
  }
  </code></pre>