Does Android XML Layout's 'include' Tag Really Work?

Question

I am unable to override attributes when using <include> in my Android layout files. When I searched for bugs, I found Declined Issue 2863:

"include tag is broken (overriding layout params never works)"

Since Romain indicates this works in the test suites and his examples, I must be doing something wrong.

My project is organized like this:

res/layout   buttons.xml  res/layout-land   receipt.xml  res/layout-port   receipt.xml 

The buttons.xml contains something like this:

<LinearLayout      xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:orientation="horizontal">    <Button .../>    <Button .../> </LinearLayout> 

And the portrait and landscape receipt.xml files look something like:

<LinearLayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:orientation="vertical">    ...    <!-- Overridden attributes never work. Nor do attributes like        the red background, which is specified here. -->   <include       android:id="@+id/buttons_override"       android:background="#ff0000"       android:layout_width="fill_parent"       layout="@layout/buttons"/>  </LinearLayout> 

What am I missing?

Answer 1

I just found the issue. First, you can only override layout_* attributes, so the background won't work. That is documented behavior and simply an oversight on my part.

The real problem is found in LayoutInflater.java:

// We try to load the layout params set in the <include /> tag. If // they don't exist, we will rely on the layout params set in the // included XML file. // During a layoutparams generation, a runtime exception is thrown // if either layout_width or layout_height is missing. We catch // this exception and set localParams accordingly: true means we // successfully loaded layout params from the <include /> tag, // false means we need to rely on the included layout params. ViewGroup.LayoutParams params = null; try {    params = group.generateLayoutParams(attrs); } catch (RuntimeException e) {    params = group.generateLayoutParams(childAttrs); } finally {    if (params != null) {      view.setLayoutParams(params);    } } 

If the <include> tag does not include both layout_width and layout_height, the RuntimeException occurs and is silently handled, without any log statement even.

The solution is to always include both layout_width and layout_height when using the <include> tag, if you want to override any of the layout_* attributes.

My example should change to:

<include       android:id="@+id/buttons_override"       android:layout_width="fill_parent"       android:layout_height="wrap_content"       layout="@layout/buttons"/> 

Answer 2

I submitted an enhancement request to allow all included attributes to be overridden:

Suppose I have two identical layouts other than the values of a TextView field. Presently, I either have modify the layout at runtime or duplicate the XML.

For example to pass two parameters with values "hello" and "world" to layout1:

<include layout="@layout/layout1a" params="textView=hello|editText=world" />

layout1a.xml:

<merge><TextView text="@param/textView"><EditText hint="@param/editText"></merge>

An alternate implementation would break encapsulation and would allow the include statement to override values like:

<include layout="@layout/layout1b" overrides="@id/textView.text=hello|@id/editText.hint=world" />

layout1b.xml:

<merge><TextView id="@+id/textView"><EditText hint="@+id/editText"></merge>