How I can remove the unnecessary top padding of the Navigation view?

NavigationView seeks to match the material design specs for the navigation drawer which state an 8dp space between content areas. Generally there are no ways to override NavigationView to specifically break the specifications.

You should read the Ian's answer. The NavigationView follows the Material guidelines and you should not break these specs.

However, currently, you can override this value in your project.

Just add to your dimens.xml:

<dimen name="design_navigation_separator_vertical_padding">0dp</dimen>

Warning:

• in the future the Android Team can change this value!
• the same value is applied to each separator in the list

The NavigationView uses a LinearLayout as header view. You can see this layout in the source code:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical"
      android:paddingBottom="@dimen/design_navigation_separator_vertical_padding" />

You can override predefined dimensions at your dimens.xml as;

<dimen name="design_navigation_padding_top_default" tools:override="true">0dp</dimen>
<dimen name="design_navigation_separator_vertical_padding" tools:override="true">0dp</dimen>
<dimen name="design_navigation_padding_bottom" tools:override="true">0dp</dimen>

Other possible values are here: https://github.com/android/platform_frameworks_support/blob/master/design/res/values/dimens.xml

very simple step : add the following attribute to your base application theme (stylename=AppTheme) Style.xml :

        <item name="listPreferredItemHeightSmall">18dp</item>