Material design - left margins for action bar title and content don't match

Question

I'm trying to set screen margins following the guidelines for Layout - Metrics and keylines. Specifically, list content on mobile screens should have a margin of 72 dp and align with the title as shown in the guide:

As Android Studio automatically generates margin values in the res/dimens.xml, I thought that I'd get my content to align with the title by adding my own 'inner' margin:

dimens.xml

<resources>
    <!-- Default screen margins, per the Android Design guidelines. -->
    <dimen name="activity_horizontal_margin">16dp</dimen>
    <dimen name="activity_vertical_margin">16dp</dimen>

    <!-- 16 + 56 = 72 = "Content left margin from screen edge" -->
    <dimen name="content_horizontal_margin">56dp</dimen>
</resources>

myactivity.xml

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin">

    <TextView
        android:id="@+id/tvEditPlaylistInfo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="@dimen/content_horizontal_margin"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="test" />

    <ImageButton
        android:layout_width="36dp"
        android:layout_height="36dp"
        android:src="@drawable/action_current"
        android:layout_alignBottom="@id/tvEditPlaylistInfo"
        android:layout_toRightOf="@id/tvEditPlaylistInfo"
        android:layout_marginLeft="16dp"/>

    <ListView
        android:id="@+id/lvAudioFiles"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="@dimen/content_horizontal_margin"
        android:layout_below="@id/tvEditPlaylistInfo">
    </ListView>

</RelativeLayout>

But somehow my content is "off" by about 8dp (emulator, Lollipop 22).

I'm using a custom theme with parent Theme.AppCompat.Light.DarkActionBar but I only changed colors so I think that is not the source of my problem.

What am I missing?

Answer 1

Remove this from your TextView and ListView:

android:layout_marginLeft="@dimen/content_horizontal_margin"

Your parent tag already specifies what the padding should be:

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin">

The reason why it is off is because you are padding, and then setting a margin.

Also, just for interest, here is The difference between Padding and Margin.

UPDATE

As per the discussion with @0X0nosugar, we've come to a point where the following code assists with achieving your objective:

In order to alter the ActionBar, the following should be added to your onCreate():

ActionBar actionBar = getSupportActionBar(); 

if (actionBar != null) 
{ 
    View customView = getLayoutInflater().inflate(R.layout.custom_action_bar, null); 
    actionBar.setDisplayShowTitleEnabled(false); 
    actionBar.setDisplayShowCustomEnabled(true); 
    actionBar.setCustomView(customView); 
}

Create a custom view for the toolbar

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:background="@color/accent_deeporangeA400" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

<TextView 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="MyMusicApp" 
    android:id="@+id/ab_title" 
    android:layout_centerVertical="true" 
    android:layout_alignParentLeft="true" 
    android:layout_marginLeft="@dimen/activity_horizontal_margin" 
    android:textAppearance="?android:attr/textAppearanceLarge"/> 

</RelativeLayout>

This should help you achieve your objective! Good researching on your part!