How to add margin between tabs in TabLayout?

Here is Kotlin version of @Todor Kostov's answer.

 for (i in 0 until applicationList_tabLayout.tabCount) {
            val tab = (applicationList_tabLayout.getChildAt(0) as ViewGroup).getChildAt(i)
            val p = tab.layoutParams as ViewGroup.MarginLayoutParams
            p.setMargins(10, 0, 10, 0)
            tab.requestLayout()
 }

Here's how I did it in pure xml.

dimens.xml:

<!-- Set this to 50% of what you want the actual space between the tabs to be. -->
<dimen name="tab_spacing_half">5dp</dimen> <!-- i.e., 10dp spacing between tabs. -->

Layout containing your TabLayout:

<android.support.design.widget.TabLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="@dimen/tab_spacing_half"/>

Add this to your theme in styles.xml:

<item name="tabBackground">@drawable/tab_background</item>

drawable-nodpi\tab_background.xml:

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

    <item
        android:drawable="@drawable/tab_background_selected"
        android:state_selected="true" />

    <item
        android:drawable="@drawable/tab_background_unselected"
        android:state_selected="false"
        android:state_focused="false"
        android:state_pressed="false" />

</selector>

drawable-nodpi\tab_background_selected.xml:

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

    <item
        android:left="@dimen/tab_spacing_half"
        android:right="@dimen/tab_spacing_half"
        android:top="@dimen/tab_spacing_half"
        android:bottom="@dimen/tab_spacing_half">

        <shape
            android:shape="rectangle">

            <corners
                android:radius="@dimen/border_radius_small">
            </corners>

            <stroke
                android:width="@dimen/divider_height_thick"
                android:color="@color/white">
            </stroke>

        </shape>

    </item>

</layer-list>

...That's where the trick is. Effectively, wrapping your background shape in an item with "padding" according to your @dimen/tab_spacing_half value. And finally...

drawable-nodpi\tab_background_unselected.xml:

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

    <item
        android:left="@dimen/tab_spacing_half"
        android:right="@dimen/tab_spacing_half"
        android:top="@dimen/tab_spacing_half"
        android:bottom="@dimen/tab_spacing_half">

        <shape
            android:shape="rectangle">

            <corners
                android:radius="@dimen/border_radius_small">
            </corners>

            <stroke
                android:width="@dimen/divider_height_thin"
                android:color="@color/white">
            </stroke>

        </shape>

    </item>

</layer-list>

Ok mates, after spending 2-3 hours on that I finally found a solution.

If you are using TabLayout there is no way to add margins to the tabs by using styles and so on. (as @Connecting life with Android earlier)

But, you can do that by writing some Java code. All in all your code should look similar to that one:

            for(int i=0; i < mTabLayout.getTabCount(); i++) {
                View tab = ((ViewGroup) mTabLayout.getChildAt(0)).getChildAt(i);
                ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) tab.getLayoutParams();
                p.setMargins(0, 0, 50, 0);
                tab.requestLayout();
            }

In order to get each and every tab as a View we have to first get the container which contains them. In this case the TabLayout is using a SlidingTabStrip as a container for the tabs. The SlidingTabStrip is the first child of the TabLayout:

View tab = ((ViewGroup) mTabLayout.getChildAt(0))

And after this small detail, everything is pretty straight forward.

@Todor Kostov answered well, but the center of the tabs are slipped away because the last tab has margin too.

so use mTabLayout.getTabCount() - 1 instead of just mTabLayout.getCodeCount().

        for(int i=0; i < mTabLayout.getTabCount() - 1; i++) {
            View tab = ((ViewGroup) mTabLayout.getChildAt(0)).getChildAt(i);
            ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) tab.getLayoutParams();
            p.setMargins(0, 0, 50, 0);
            tab.requestLayout();
        }