Android ScrollView Overlaps - Weight? -

i have following layout, , reason scrollview overlaps on views. don't quite understand whole use of weight , layout_weight attribute in android. thinking has problem.

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/list"     android:layout_width="match_parent"     android:layout_height="match_parent" >      <imageview         android:id="@+id/topbar"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_alignparentright="true"         android:layout_alignparenttop="true"         android:adjustviewbounds="true"         android:scaletype="fitxy"          />      <imageview         android:id="@+id/secondbar"         android:adjustviewbounds="true"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_alignparentleft="true"         android:layout_below="@+id/topbarr"         android:scaletype="fitxy"           />      <scrollview         android:id="@+id/buttonlistview"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:layout_alignparentleft="true"         android:layout_alignparenttop="true"         android:layout_below="@+id/secondbar"         android:scrollbarfadeduration="0"          >     </scrollview>    </relativelayout> 

firstly, should have 1 view android:layout_alignparenttop="true" if want views 1 below another.

secondly, need use @+id once each variable. once it's declared, refer @id.

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/list"     android:layout_width="match_parent"     android:layout_height="match_parent" >      <imageview         android:id="@+id/topbar"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_alignparentright="true"         android:layout_alignparenttop="true"         android:adjustviewbounds="true"         android:scaletype="fitxy"          />      <imageview         android:id="@+id/secondbar"         android:adjustviewbounds="true"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_alignparentleft="true"         android:layout_below="@id/topbar"         android:scaletype="fitxy"           />      <scrollview         android:id="@+id/buttonlistview"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:layout_alignparentleft="true"         android:layout_below="@id/secondbar"         android:scrollbarfadeduration="0"          >     </scrollview>  </relativelayout>