ANDROID Background for LinearLayouts

i used nested LinearLayouts for the purpose of putting the EditTexts and Buttons in the center of the screen like this:

I want to change the background of this. So I inserted another LinearLayout on the top of everything else. But its not working. All I can see is black which indicates that I have covered the Editext and Buttons.

I think have to arrange the layouts properly.

any suggestions on how i may put a background(i.e. color, as of now)?

I am posting my xml.

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:background="@+id/OceanBlue">
<LinearLayout 
      android:orientation="vertical"
      android:layout_width="wrap_content">
<LinearLayout
         android:orientation="horizontal"
         android:layout_width="fill_parent"
     开发者_开发技巧    android:layout_height="wrap_content"
         android:gravity="right" >              
        <EditText
             android:id="@+id/et_username"
             android:layout_width="170px"
             android:layout_height="wrap_content"/> 
</LinearLayout>


<LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">           
        <EditText
             android:id="@+id/et_password"          
             android:password="true"
             android:layout_width="170px"
             android:layout_height="wrap_content"/>
</LinearLayout>

<LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">   
        <Button
            android:id="@+id/button_ok"
            android:text="Login"    
            android:layout_width="86px"
            android:layout_height="wrap_content">

        </Button>

        <Button
            android:id="@+id/button_cancel"
            android:text="Cancel">  
         </Button>
</LinearLayout>
</LinearLayout>

---

I dont know how you are getting this without specifying any layout_height or layout_width

Use

android:layout_width="fill_parent"
android:layout_height="fill_parent" 

in your main parent linear layout.I think it will solve your issue.

---

Are you able to see the layout, thats unexpected? You did not specify the height or width for parent layout so i think that is the problem.
In case of having these kinds of designs its better to use relative layout which provides main features to deign the layout as our wish