title: Is there a way to make AppCompat's ActionBar's "back/up" button act as the "back" system button
body: <p>I have an app with a couple of activities. Until now I had a "hardcoded" hierarchy between them, so I had the android:parentActivityName set explicitly in each (but the launcher activity) of them. However now I added the Settings to the menu of more than one activity.</p>
  
  <p>Is there a way to make the "back" arrow in the action bar function as the system's back button (in the bottom of the screen)? In other words: if there's a parentActivityName set, then it goes back to the parent activity, if not, then it closes the activity and "goes back" to the previous activity.</p>
  
  <p>This is what I tried, but doesn't work. If I don't call actionBar.setDisplayHomeAsUpEnabled(true), then there's no "back" arrow in the action bar, but if I call it in an activity that doesn't have parentActivityName set in the Manifest, then I get an exception when I click the arrow.</p>
  
  <pre><code>abstract public class BaseActivity extends ActionBarActivity {
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(getLayoutResourceId());
  
          final ActionBar actionBar = getSupportActionBar();
          if (null != actionBar) {
              actionBar.setDisplayHomeAsUpEnabled(getDisplayHomeAsUpEnabled());
          }
      }
  
      protected abstract int getLayoutResourceId();
      abstract protected boolean getDisplayHomeAsUpEnabled();
  
      @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.
          final int id = item.getItemId();
          if (id == android.R.id.home) {
              NavUtils.navigateUpFromSameTask(this);
              return true;
          }
      }
  }
  </code></pre>