get checkbox state inside GridView with RelativeLayout

I have GridView with more Checkbox and i need know what is the checkBox state. As stated at the end of the post i received error when i insert RelativeLayout, ImageView and TextView in my XML.

i received this log:

 05-05 22:03:29.375: E/AndroidRuntime(3443): FATAL EXCEPTION: main
 05-05 22:03:29.375: E/AndroidRuntime(3443): Process:       com.kirolm.instalacionesdep, PID: 3443
 05-05 22:03:29.375: E/AndroidRuntime(3443):     java.lang.NullPointerException
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.kirolm.instalacionesdep.search.BuscarInstalacionesActividadFragment.ge    tItemCheked(BuscarInstalacionesActividadFragment.java:218)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.kirolm.instalacionesdep.search.BuscarInstalacionesActividadFragment.on    OptionsItemSelected(BuscarInstalacionesActividadFragment.java:123)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.app.Fragment.performOptionsItemSelected(Fragment.java:1806)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.app.FragmentManagerImpl.dispatchOptionsItemSelected(FragmentManager.java:1972)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.app.Activity.onMenuItemSelected(Activity.java:2603)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1065)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:741)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:884)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:546)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:115)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.view.View.performClick(View.java:4445)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.view.View$PerformClick.run(View.java:18446)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.os.Handler.handleCallback(Handler.java:733)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.os.Handler.dispatchMessage(Handler.java:95)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.os.Looper.loop(Looper.java:136)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at android.app.ActivityThread.main(ActivityThread.java:5146)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at java.lang.reflect.Method.invokeNative(Native Method)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at java.lang.reflect.Method.invoke(Method.java:515)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
 05-05 22:03:29.375: E/AndroidRuntime(3443):    at dalvik.system.NativeStart.main(Native Method)

I have this XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://ift.tt/nIICcg"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

    <RelativeLayout 
android:layout_width="match_parent"
android:layout_height="wrap_content" 
android:gravity="center">

            <ImageView
        android:id="@+id/buscar_instalaciones_actividad_fragment_imageview_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true" 
        android:scaleType="center"
        android:src="@drawable/header_buscar_actividad" />

            <TextView
        android:id="@+id/buscar_instalaciones_actividad_fragment_tv_titulo_header"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:gravity="center_horizontal"
                      android:text="@string/buscar_instalaciones_actividad_fragment_titulo_header"
                      android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>

    <GridView
        android:id="@+id/buscar_instalaciones_actividad_fragment_gridview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:horizontalSpacing="0dp"
        android:numColumns="4"
        android:stretchMode="columnWidth"
        android:verticalSpacing="0dp" >
    </GridView>

and this is my getItemChecked() method:

    public ArrayList<String> getItemCheked(){
    ArrayList<String> checkResultArray = new ArrayList<String>();

    int count = grid.getAdapter().getCount();
    for(int i = 0; i < count; i++){
        RelativeLayout itemLayout = (RelativeLayout)grid.getChildAt(i);
        CheckBox chb = (CheckBox) itemLayout.findViewById(R.id.buscar_instalaciones_actividad_activity_grid_item_chb);
        if(chb.isChecked()){
            String valor = (String) chb.getTag();
            checkResultArray.add(valor);
            Log.e("Checking", "BuscarInstalacionesActividadActivity: El boton pulsado es: "+valor );
        }
    }
    return checkResultArray;
}

The line 218 is this:

CheckBox chb = (CheckBox) itemLayout.findViewById(R.id.buscar_instalaciones_actividad_activity_grid_item_chb);

If i delete this in my xml, it runs ok, but i need that RelativeLayout, ImageView and textView.

        <RelativeLayout 
android:layout_width="match_parent"
android:layout_height="wrap_content" 
android:gravity="center">
            <ImageView
        android:id="@+id/buscar_instalaciones_actividad_fragment_imageview_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true" 
        android:scaleType="center"
        android:src="@drawable/header_buscar_actividad" />

                  <TextView
                      android:id="@+id/buscar_instalaciones_actividad_fragment_tv_titulo_header"
                      android:layout_width="wrap_content"
                      android:layout_height="wrap_content"
                      android:layout_centerHorizontal="true"
                      android:layout_centerVertical="true"
                      android:gravity="center_horizontal"
                      android:text="@string/buscar_instalaciones_actividad_fragment_titulo_header"
                      android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>