Declaring AlertDialog Builder:Challenge1:Adding camera and video Button-Build self Destructing android app

import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.view.MenuItem;

public class MainActivity extends Activity {

    protected DialogInterface.OnClickListener mDialogListener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {

        }
    };

    // Some code omitted!

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();

        switch(itemId) {        
            case R.id.action_button:
                break;
          AlertDialog.Builder builder = new AlertDialog.Builder(this);
        }

        return super.onOptionsItemSelected(item);
    }
}