Rotate the Activity with click on a Button

Question

I am using this CODE to disable the auto rotate in my App:

            android:screenOrientation="portrait"

What I want is to write a CODE inside my Activity to make the App on portrait or landscape as the user want by clicking a button and save it in SharedPreferences.

I am already made layout and layout-land with different design but as i disabled it in my Manifest its is not showing up, Cause i want the users chose what they want!

Thanks for any Help

UPDATE

    /** Here is the Rotation Button */
View.OnClickListener mb2 = new View.OnClickListener() {
    public void onClick(View v) {
        startActivity(new Intent(".ABOUT"));
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

    }
};

It doesn't work this way!

Answer 1

     iv_fullScreenVideo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            int orientation = context.getResources().getConfiguration().orientation;

            switch (orientation) {

                case Configuration.ORIENTATION_LANDSCAPE:

                    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

                    break;

                case Configuration.ORIENTATION_PORTRAIT:

                    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

                    break;
            }

        }
    });

Answer 2

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

or

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);