Undeclared namespace prefix "android" (for attribute "layout_width")

How can I fix this? This says that android is not defined. How can I solve it? please help

CodePudding user response：

try to add this in the layout

xmlns:android="http://schemas.android.com/apk/res/android

here is an example:

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

CodePudding user response：

Try to check some of these.

1. You see this error with an incorrect namespace, or a typo in the attribute. Like 'xmlns' is wrong, it should be xmlns:android

2. First node needs to contain: xmlns:android="http://schemas.android.com/apk/res/android"

3. If you are integrating AdMob, check custom parameters like ads:adSize, you need

xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"

4. If you are using LinearLayout you might have to define tools:

xmlns:tools="http://schemas.android.com/tools"