Why AndroidStudio shows warning "Namespace declaration is never used"?

Question

This is my layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >
</LinearLayout>

Taked from the android official training

In the second line, AndroidStudio shows this warning:

Namespace declaration is never used

Why this happens?

Thank you.

Priedieu

The statement that the tools namespace is not used is perfectly correct, but I've no idea why the parser chooses to report this as a warning, since unused namespaces normally do no harm. – Experimentalism

Yes, But I think having an unused namespace is like having an unused variable or method. So by default the ide warns the unnecessary code. – Priedieu

Well, warnings are a matter of opinion, but so many XML-generation processes produce XML with redundant namespaces that in my view, a tool that warns about them is going to get very irritating. Also, you can't automatically detect that a namespace declaration is redundant; it might be used only (as in XSLT) to declare prefixes used by QNames-in-content. – Experimentalism

How you said, "warnings are a matter of opinion". In my opinion is good thing the ide warns unused things, even in xml. – Priedieu

Answer 1

This is because you don't have anything with tools namespace actually declared in your xml.

Look at the android namespace, you have 3 elements with that namespace, but none for tools.

The namespace tools (http://schemas.android.com/tools) is used for the GUI designer and is not used for running apps on Android devices so you can safely remove it.

Photoplay

Answer 2

just remove "xmlns:app="http://schemas.android.com/apk/res-auto""

Devisor

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