OnItemClickListener Navigation Drawer

Instead of your code:

private void selectItem(int position) {

    Fragment fragment = new GalaxyFragment();
    Bundle args = new Bundle();
    args.putInt(GalaxyFragment.ARG_Galaxy_NUMBER, position);
    fragment.setArguments(args);

    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();


    mDrawerList.setItemChecked(position, true);
    setTitle(mGalaxyTitles[position]);
    mDrawerLayout.closeDrawer(mDrawerList);
}

Use this code:

private void selectItem(int position) {
    switch(position) {
    case 1:
            Intent a = new Intent(MainActivity.this, Activity1.class);
            startActivity(a);
    break;
    case 2:
            Intent b = new Intent(MainActivity.this, Activity2.class);
           startActivity(b);
           break;
    default:
    }
}

And remove this part: (It is not necessary)

public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

switch(position) {
case 1:
        Intent a = new Intent(MainActivity.this, Page1.class);
        startActivity(a);
break;
case 2:
        Intent b = new Intent(MainActivity.this, Page2.class);
       startActivity(b);
       break;
default:
}
}