Android : How to disable recents button in android?

I am designing an app that should be the only app on the tablet, and the user should not see anything else, and should not be able to change the settings.I have set the activity to be fullscreen, so the user can't see the notification bar. Here is my intent filter for the activity.

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.HOME" />
        <category android:name="android.intent.category.LAUNCHER" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>

I also overrided the back button because I had some problems with that. Now my question is, the home button and back button do not work, and that's fine for me, the notification bar is also hidden for the user as the activity is fullscreen, but the recents button gives the user ability to access the notification bar.

I tried this solution

How to disable the Recent Tasks/Apps button in Android

but in that case, when the recents button is pressed, it's opening the recents tab and closing again, so the user sees the blinking activity, which is undesirable. How can I just make the button do nothing?