react-native-scrollable-tab-view-forked/test/android/app/src/main/res/values/styles.xml

forked react-native-scrollable-tab-view ,you can set line width

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="android:textColor">#000000</item>
    </style>

</resources>