How do I remove the boundary between action and toolbar?
Bad Case
Good Case, I want to like it.
Activity XML
Fragment XML
What you are looking for is a way to remove the shadow under toolbar.
For android 4.4 or below, you will have to set the window content overlay in your activity theme like this
<style name="Theme.MyApp" parent="Theme.AppCompat.Light.NoActionBar">
...
<!--To hide shadow effect in toolbar for Android 4.4 or below-->
<item name="android:windowContentOverlay">@null</item>
</style>
For Android 5.0+, you will also need to set the toolbar elevation to 0 in the activity layout like this.
<LinearLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
...
>
<android.support.design.widget.AppBarLayout
...
app:elevation="0dp">
...
</android.support.design.widget.AppBarLayout>
</LinearLayout>
Actually, many people ask about this. See answer here
Try to search for existing answer next time ;)