Android删除导航抽屉上的阴影

嗨,我正在使用股票导航抽屉v4,我问如何在导航抽屉打开时删除该背景阴影.

这是我的NavigationDrawerFragment.java代码

public void setUp(int fragmentId,DrawerLayout drawerLayout) {
    mFragmentContainerView = getActivity().findViewById(fragmentId);
    mDrawerLayout = drawerLayout;

    // set a custom shadow that overlays the main content when the drawer opens
    mDrawerLayout.setDrawerShadow(R.drawable.trasparent,GravityCompat.START);
    // set up the drawer's list view with items and click listener

    ActionBar actionBar = getActionBar();
    actionBar.setdisplayHomeAsUpEnabled(true);
    actionBar.setHomeButtonEnabled(true);

这是MainActivity.xml

<android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Main layout -->
    <FrameLayout
        android:id="@+id/main_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


    <ImageView
        android:id="@+id/ImageView3_Left"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

    <!-- The navigation drawer -->
    <ListView android:id="@+id/left_drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:background="#FFFFFFFF"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"/>

</android.support.v4.widget.DrawerLayout>