Try the modified xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnCount="1"
android:orientation="vertical" >
<ImageButton
android:id="@+id/AlertBtn"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="fill_horizontal"
android:layout_weight="1"
android:src="@drawable/mylocation" />
<ImageButton
android:id="@+id/myLocationBtn"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="fill_horizontal"
android:layout_weight="1"
android:src="@drawable/proximity" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="fill_horizontal"
android:layout_weight="1"
android:src="@drawable/title" />
</LinearLayout>
let me know.. what do you think
If you want to remove the button background add this to the ImageButton
android:background="@null"
after removing the background for the button set you own custom background color or image in the parent linearlayout like this
android:background="#DCDCDC"