Ndtyjky

First error solved, please read my comment on Daniel Haley's answer.

I pretty new to Android developing and used changed the size of a picture in a layout XML file.

Since then im always getting this error:

Error:(1, 151) The attribute type is required in the declaration of attribute "CDATA" for element "LinearLayoutxmlns:android".

And I have no idea, what it's telling me... Google only seems to give me very few results all with similar code.

Here is the content of my XML file:

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE LinearLayout [<!ELEMENT LinearLayout (ImageView|TextView)*><!ATTLIST LinearLayoutxmlns:android CDATA #REQUIREDandroid:layout_width CDATA #REQUIREDandroid:layout_height CDATA #REQUIREDandroid:background CDATA #REQUIREDandroid:gravity CDATA #REQUIREDandroid:orientation CDATA #REQUIREDandroid:paddingBottom CDATA #REQUIREDandroid:paddingLeft CDATA #REQUIREDandroid:paddingRight CDATA #REQUIREDandroid:paddingTop CDATA #REQUIREDandroid:theme CDATA #REQUIRED><!ELEMENT ImageView (#PCDATA)><!ATTLIST ImageViewandroid:id CDATA #REQUIREDandroid:layout_width CDATA #REQUIREDandroid:layout_height CDATA #REQUIREDandroid:paddingTop CDATA #REQUIREDandroid:src CDATA #REQUIRED><!ELEMENT TextView (#PCDATA)><!ATTLIST TextViewandroid:layout_width CDATA #REQUIREDandroid:layout_height CDATA #REQUIREDandroid:layout_gravity CDATA #REQUIREDandroid:layout_marginLeft CDATA #REQUIREDandroid:layout_marginTop CDATA #REQUIREDandroid:text CDATA #REQUIREDandroid:textSize CDATA #REQUIREDandroid:textStyle CDATA #REQUIRED>]>

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

    android:layout_width="match_parent"

    android:layout_height="@dimen/nav_header_height"

    android:background="@drawable/side_nav_bar"

    android:gravity="bottom"

    android:orientation="horizontal"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    android:theme="@style/ThemeOverlay.AppCompat.Dark">



    <ImageView

        android:id="@+id/imageView"

        android:layout_width="@dimen/_80sdp"

        android:layout_height="@dimen/_80sdp"

        android:paddingTop="@dimen/nav_header_vertical_spacing"

        android:src="@drawable/pyroappappicon" />



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="match_parent"

        android:layout_gravity="center_vertical"

        android:layout_marginLeft="@dimen/_10sdp"

        android:layout_marginTop="@dimen/_30sdp"

        android:text="@string/app_name"

        android:textSize="@dimen/_20sdp"

        android:textStyle="bold" />



</LinearLayout>

In the attlist declarations, your attribute names aren't separated by spaces.

For example LinearLayoutxmlns:android (from the error message) should be LinearLayout xmlns:android.

Another example is #REQUIREDandroid:layout_width should be #REQUIRED android:layout_width.

Here's a version with the attlist declarations fixed.

It validates now but since I don't know anything about android development I don't know what changes you made and if they're going to work the way you intended.

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE LinearLayout [

<!ELEMENT LinearLayout (ImageView|TextView)*>

<!ATTLIST LinearLayout

    xmlns:android CDATA #REQUIRED

    android:layout_width CDATA #REQUIRED

    android:layout_height CDATA #REQUIRED

    android:background CDATA #REQUIRED

    android:gravity CDATA #REQUIRED 

    android:orientation CDATA #REQUIRED 

    android:paddingBottom CDATA #REQUIRED 

    android:paddingLeft CDATA #REQUIRED 

    android:paddingRight CDATA #REQUIRED 

    android:paddingTop CDATA #REQUIRED 

    android:theme CDATA #REQUIRED>

<!ELEMENT ImageView (#PCDATA)>

<!ATTLIST ImageView

    android:id CDATA #REQUIRED

    android:layout_width CDATA #REQUIRED

    android:layout_height CDATA #REQUIRED

    android:paddingTop CDATA #REQUIRED

    android:src CDATA #REQUIRED>

<!ELEMENT TextView (#PCDATA)>

<!ATTLIST TextView

    android:layout_width CDATA #REQUIRED

    android:layout_height CDATA #REQUIRED

    android:layout_gravity CDATA #REQUIRED

    android:layout_marginLeft CDATA #REQUIRED

    android:layout_marginTop CDATA #REQUIRED

    android:text CDATA #REQUIRED

    android:textSize CDATA #REQUIRED

    android:textStyle CDATA #REQUIRED>

]>

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

    android:layout_width="match_parent"

    android:layout_height="@dimen/nav_header_height"

    android:background="@drawable/side_nav_bar"

    android:gravity="bottom"

    android:orientation="horizontal"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    android:theme="@style/ThemeOverlay.AppCompat.Dark">



    <ImageView

        android:id="@+id/imageView"

        android:layout_width="@dimen/_80sdp"

        android:layout_height="@dimen/_80sdp"

        android:paddingTop="@dimen/nav_header_vertical_spacing"

        android:src="@drawable/pyroappappicon" />



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="match_parent"

        android:layout_gravity="center_vertical"

        android:layout_marginLeft="@dimen/_10sdp"

        android:layout_marginTop="@dimen/_30sdp"

        android:text="@string/app_name"

        android:textSize="@dimen/_20sdp"

        android:textStyle="bold" />



</LinearLayout>

Here's another version with the doctype declaration all on one line like the original:

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE LinearLayout [<!ELEMENT LinearLayout (ImageView|TextView)*><!ATTLIST LinearLayout xmlns:android CDATA #REQUIRED android:layout_width CDATA #REQUIRED android:layout_height CDATA #REQUIRED android:background CDATA #REQUIRED android:gravity CDATA #REQUIRED android:orientation CDATA #REQUIRED android:paddingBottom CDATA #REQUIRED android:paddingLeft CDATA #REQUIRED android:paddingRight CDATA #REQUIRED android:paddingTop CDATA #REQUIRED android:theme CDATA #REQUIRED><!ELEMENT ImageView (#PCDATA)><!ATTLIST ImageView android:id CDATA #REQUIRED android:layout_width CDATA #REQUIRED android:layout_height CDATA #REQUIRED android:paddingTop CDATA #REQUIRED android:src CDATA #REQUIRED><!ELEMENT TextView (#PCDATA)><!ATTLIST TextView android:layout_width CDATA #REQUIRED android:layout_height CDATA #REQUIRED android:layout_gravity CDATA #REQUIRED android:layout_marginLeft CDATA #REQUIRED android:layout_marginTop CDATA #REQUIRED android:text CDATA #REQUIRED android:textSize CDATA #REQUIRED android:textStyle CDATA #REQUIRED>]>

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

    android:layout_width="match_parent"

    android:layout_height="@dimen/nav_header_height"

    android:background="@drawable/side_nav_bar"

    android:gravity="bottom"

    android:orientation="horizontal"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    android:theme="@style/ThemeOverlay.AppCompat.Dark">



    <ImageView

        android:id="@+id/imageView"

        android:layout_width="@dimen/_80sdp"

        android:layout_height="@dimen/_80sdp"

        android:paddingTop="@dimen/nav_header_vertical_spacing"

        android:src="@drawable/pyroappappicon" />



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="match_parent"

        android:layout_gravity="center_vertical"

        android:layout_marginLeft="@dimen/_10sdp"

        android:layout_marginTop="@dimen/_30sdp"

        android:text="@string/app_name"

        android:textSize="@dimen/_20sdp"

        android:textStyle="bold" />



</LinearLayout>