Attempt to invoke virtual method 'void android.app.ActionBar.hide()' on a null object reference

今天在使用DrawerLayout时遇到了NullPointerException(空指针异常)问题：Caused by: java.lang.NullPointerException: Attempt to invoke virtual method ‘void android.app.ActionBar.hide()’ on a null object reference

贴上错误的代码：

public class MainActivity extends **FragmentActivity** {

private DrawerLayout mDrawerLayout;
private RelativeLayout rightLayout;
private List<ContentModel> list;
private ContentAdapter adapter;
private ImageView leftMenu,rightMenu;
private ListView listView;
private FragmentManager frgmentManager;

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

**getActionBar().hide();**

错误原因：

if you are using the support library then you have to use getSupportActionBar() instead of getActionBar(), and instead of extends Activity you have to extends AppCompactActivity

译文：如果您使用的支持库然后你必须使用 getSupportActionBar() 而不是 getActionBar()，你要继承 AppCompactActivity而不是继承的Activity。

修改之后的代码：

public class MainActivity extends **AppCompatActivity** {

private DrawerLayout mDrawerLayout;
private RelativeLayout rightLayout;
private List<ContentModel> list;
private ContentAdapter adapter;
private ImageView leftMenu,rightMenu;
private ListView listView;
private FragmentManager frgmentManager;

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

**getSupportActionBar().hide();**

修改之后编译结果正确。。。

StackOverFlow的解释：

[]http://stackoverflow.com/questions/27235501/actionbar-giving-nullpointerexception]