抽屉式导航无法关闭

我的应用程序中的导航抽屉没有关闭。我正在使用活动而不是片段。当我单击中的任何项目时listview，它会按应有的方式打开其他活动，但当我回去时，抽屉仍然打开。我尝试过使用DrawerLayout.closeDrawers();但它不起作用。如何关闭抽屉式导航栏？
这是我的代码：

Java

public class MainActivity extends FragmentActivity {
final String[] data ={"Aluminium","Gold","Zinc"};

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

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, data);

    final DrawerLayout drawer = (DrawerLayout)findViewById(R.id.drawer_layout);
    final ListView navList = (ListView) findViewById(R.id.left_drawer);
    navList.setAdapter(adapter);
    navList.setOnItemClickListener(new AdapterView.OnItemClickListener(){
        @Override
        public void onItemClick(AdapterView<?> parent, View view, final int pos,long id){

            switch (pos){
                case 0:
                    Intent i = new Intent(MainActivity.this,Aluminium.class);
                    startActivity(i);
                    break;
                case 1:
                    Intent i2 = new Intent(MainActivity.this,Gold.class);
                    startActivity(i2);
                    break;
                case 2:
                    Intent i3 = new Intent(MainActivity.this,Zinc.class);
                    startActivity(i3);
                    break;
            }
        }
    });
}
}

XML

<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:background="#000000"
    android:layout_height="match_parent" >
</FrameLayout>

<ListView android:id="@+id/left_drawer"
    android:layout_width="220dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:choiceMode="singleChoice"
    android:divider="@android:color/transparent"
    android:dividerHeight="1dp"
    android:background="#000000"/>
</android.support.v4.widget.DrawerLayout>

你有没有尝试过 ：

mDrawerLayout.closeDrawer(drawerListView);

您可以在调用之前添加此内容startActivity()