Reference the id of a view inside an "include" layout in xml

Question

I have a button, A, inside special_button.xml, that I reuse on all my activities. Each activity has a root RelativeLayout.

The problem: one of my activities has a button, B, on the same position as A. I decided to just move B above A, but I can't reference A from the activity's xml.

Here are the xmls

special_button.xml

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android" >

    <Button
        android:id="@+id/A"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="15dp"
        android:layout_marginRight="20dp"/>

</merge>

layout_main.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" >

    <include layout="@layout/special_button" />

    <Button
        android:id="@+id/B"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_above="<id to reference button A>"
        android:layout_marginBottom="15dp"
        android:layout_marginRight="20dp" />

</RelativeLayout>

Answer 1

When you use the include tag, you should also specify a new id within that XML, which you can then reference as the id within the RelativeLayout. See the documentation and this sample code:

You can also override all the layout parameters (any android:layout_* attributes) of the included layout's root view by specifying them in the tag. For example:

<include android:id="@+id/news_title"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     layout="@layout/title"/>

EDIT: As @eskimoapps.com points out, there appears to be a known issue doing this with RelativeLayouts, as documented here, but when I run the following code, it is working as OP requests:

<?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" >

    <include layout="@layout/special_button"
        android:id="@+id/btn_a_ref"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
         />

    <Button
        android:id="@+id/B"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_above="@+id/A"     <!-- this still works, despite having warning in Eclipse -->
        android:layout_marginBottom="15dp"
        android:layout_marginRight="20dp" />

</RelativeLayout>

Here is the picture from HierarchyViewer showing the correct layout: id/A below id/B

My only thought is that Eclipse doesn't like it since it's statically trying to find the Button within the same layout file. Since <include> and <merge> work dynamically with the LayoutManager, that's probably while this still works as expected.

Please try and see if this works for you as well.