Button beneath navigation drawer not working when pressed

Yet, when the button is placed in the hierarchy so that it can be seen on top of the navigation drawer, the button functions properly. However, the button should be hidden behind the navigation drawer when it is slid out, so this is not desirable.

Below is the code from MainActivity.java

public class MainActivity extends ActionBarActivity implements NavigationDrawerCallbacks {

public ProgressDialog progBar;

public final static boolean DEBUG = false;
public final static String TAG = "AppGetter";
private Toolbar mToolbar;
private NavigationDrawerFragment mNavigationDrawerFragment;



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

    mToolbar = (Toolbar) findViewById(R.id.toolbar_actionbar);
    setSupportActionBar(mToolbar);
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    getSupportActionBar().setDisplayShowTitleEnabled(false); 

    mNavigationDrawerFragment = (NavigationDrawerFragment) getFragmentManager().findFragmentById(R.id.fragment_drawer);
    mNavigationDrawerFragment.setup(R.id.fragment_drawer, (DrawerLayout) findViewById(R.id.drawer), mToolbar);

    ImageButton cart_button = (ImageButton) findViewById(R.id.button2);
    cart_button.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View view) {
            start_request();

        }
    });



}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public void onNavigationDrawerItemSelected(int position) {
    Toast.makeText(this, "Menu item selected -> " + position, Toast.LENGTH_SHORT).show();
}

@Override
public void onBackPressed() {
    if (mNavigationDrawerFragment.isDrawerOpen())
        mNavigationDrawerFragment.closeDrawer();
    else
        super.onBackPressed();
}


public void start_request()
{
    String pkg = getPackageName();
    Intent intent = new Intent(Intent.ACTION_MAIN);
    intent.setComponent(new ComponentName(pkg,pkg+".RequestActivity"));
    startActivity(intent);

    if(DEBUG)Log.v(TAG,"Intent intent: "+intent);
}
}

I am assuming the issue lies within the class above, but for completion's sake, I pasted the two XML files of interest below.

activity_main.xml As you can see, the ImageButton is currently "above" the navigation drawer in hierarchy so as to make it be covered by the navigation drawer. Moving the ImageButton "below" makes the button work properly, but causes it to appear on top of the navigation drawer (and not tinted like the rest of the layout).

<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:fontify="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity"
    android:background="@color/myPrimaryColor">

    <View
        android:id="@+id/block1"
        android:layout_height="240dp"
        android:layout_width="match_parent"
        android:layout_below="@+id/toolbar_actionbar"
        android:background="@drawable/block_primary"
        />

    <TextView
        android:id="@+id/title1"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_below="@+id/toolbar_actionbar"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="56dp"
        android:text="@string/title"
        android:textColor="@color/white"
        android:textSize="34sp"
        android:fontFamily="sans-serif"
        />

    <include
        android:id="@+id/toolbar_actionbar"
        layout="@layout/toolbar_default"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        />

    <ImageButton
        android:id="@+id/button2"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="268dp"
        android:src="@drawable/ic_chevron_up"
        android:background="@drawable/fab_simple"/>

    <android.support.v4.widget.DrawerLayout
        android:id="@+id/drawer"
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:layout_below="@+id/toolbar_actionbar"
        >

        <FrameLayout
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

        <fragment
            android:id="@+id/fragment_drawer"
            android:name="com.onepersonco.iconrequestbase.NavigationDrawerFragment"
            android:layout_width="@dimen/navigation_drawer_width"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            layout="@layout/fragment_navigation_drawer"
            tools:layout="@layout/fragment_navigation_drawer" />
    </android.support.v4.widget.DrawerLayout>
</RelativeLayout>

fragment_navigation_drawer.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>

<!-- Provides a margin at the top of the navigation drawer. -->
<View
    android:id="@+id/navWhiteSpace1"
    android:layout_width="match_parent"
    android:layout_height="64dp"
    android:background="@color/myNavigationDrawerBackgroundColor"
    />


<android.support.v7.widget.RecyclerView
android:id="@+id/drawerList"
android:layout_below="@+id/navWhiteSpace1"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:focusableInTouchMode="true"
android:scrollbars="vertical"
android:scrollbarDefaultDelayBeforeFade="0"
android:scrollbarFadeDuration="0"
android:overScrollMode="never"
android:focusable="true"
android:background="@color/myNavigationDrawerBackgroundColor"/>

</RelativeLayout>