Unexpected namespace prefix "app" found for tag RelativeLayout - Android?

Question

I need to use BottomSheetBehavior with ScrollView but it says to me :

Unexpected namespace prefix "app" found for tag RelativeLayout

app:behavior_hideable="true"
app:behavior_peekHeight="80dp"

Here is my xml :

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/ABLList"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay">

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:gravity="end"
                    android:orientation="horizontal">

                    <ImageButton
                        android:id="@+id/imbDetail"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="end|center_vertical"
                        android:layout_marginRight="10dp"
                        android:background="@null"
                        android:src="@drawable/ic_action_detail" />
                </LinearLayout>
            </android.support.v7.widget.Toolbar>

        </android.support.design.widget.AppBarLayout>

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_OrderList"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_below="@+id/ABLList"
            android:scrollbars="vertical" />
    </RelativeLayout>

    <ScrollView
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <RelativeLayout
            android:id="@+id/layout_bottom_sheet_ListOrder"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_gravity="top"
            android:background="@color/color_bottom_sheet"
            android:gravity="top"
            app:behavior_hideable="true"
            app:behavior_peekHeight="80dp"
            app:layout_behavior="@string/string_bottom_sheet_behavior">

            <com.example.asheq.utils.TextViewJus
                android:id="@+id/txtAddress"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="@dimen/text_marginTop"
                android:gravity="right"
                android:maxLines="5"
                android:paddingLeft="@dimen/activity_vertical_margin"
                android:paddingRight="@dimen/activity_vertical_margin"
                android:textSize="@dimen/text_size"
                android:textStyle="bold" />

            <Button
                android:id="@+id/btnSReport"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txtCTime"
                android:layout_marginTop="50dp"
                android:text="@string/btnReport" />

        </RelativeLayout>
    </ScrollView>

    <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/coordinatorOrder"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true" />
</android.support.design.widget.CoordinatorLayout>

Answer 1

This issue is well known in while using data-binding in a layout.

Assume you want to use some data binding attribute with app: prefix then just adding xmlns:app... will not be enough. layout should be data binding layout wrapped with <layout tag.

Incorrect Approach:

e.g. I imported layout_toolbar_default.xml and using app:toolbarTitle to specify title.

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

    <include
        layout="@layout/layout_toolbar_default"
        app:toolbarTitle="@{@string/app_name}"
        />

</LinearLayout>

This will show error Unexpected namespace prefix "app" found.

Solution:

Wrap your layout with <layout tag because you are using binding attribute.

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

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        >

        <include
            layout="@layout/layout_toolbar_default"
            app:toolbarTitle="@{@string/app_name}"
            />

    </LinearLayout>
</layout>