Android set your application no action bar

To set your Android app no action bar first you need to create a file which is styles-v21.xml

step to create styles-v21.xml file:

Right click on res folder, choose New --> Android resource file, set the same name for the new file "styles", in Available qualifiers: choose the last item "Version" and finally set "Platform API level" 21.

After that, open the styles-v21.xml file and paste the below code inside the resource tag

 <style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="android:windowDrawsSystemBarBackgrounds">true</item>
</style>

Lastly go to android AndroidManifest.xml file apply this code inside application tag

 android:theme="@style/AppTheme.NoActionBar"

That's all, thank you, All the best =D