Fragment Will Not Switch Back View and Boolean Variable is Showing as Always False

I have an application with two fragments which will not switch back to the original from the method I am using. I have a feeling this is not the way to carry out this. Where am I going wrong? My code is below.

// region GlobalVars
boolean viewLib;
// endregion

// region Init
void Init () {
    viewLib = false;
}
// endregion

// region onCreate
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_music);
    Init();

    // Set Initial Library Fragment
    if (findViewById(R.id.fragment_container) != null) {
        if (savedInstanceState != null) {
            return;
        }
        PlayerFragment firstFragment = new PlayerFragment();
        firstFragment.setArguments(getIntent().getExtras());
        getSupportFragmentManager().beginTransaction()
                .add(R.id.fragment_container, firstFragment).commit();
    }
}
// endregion

// region SwitchView
void SwitchView () {
    if (viewLib = false) {
        Toast.makeText(getApplicationContext(), "viewLib", Toast.LENGTH_SHORT).show();
        Library();
        viewLib = true;
    } else {
        Toast.makeText(getApplicationContext(), "!viewLib", Toast.LENGTH_SHORT).show();
        Player();
        viewLib = false;
    }
}
//region Library
void Library() {
    LibraryFragment newFragment = new LibraryFragment();
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

    transaction.replace(R.id.fragment_container, newFragment);
    transaction.addToBackStack(null);

    transaction.commit();
}
// endregion

//region Player
void Player() {
    PlayerFragment newFragment = new PlayerFragment();
    //Bundle args = new Bundle();
    //args.putInt(LibraryFragment.ARG_POSITION, position);
    //newFragment.setArguments(args);
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

    transaction.replace(R.id.fragment_container, newFragment);
    transaction.addToBackStack(null);

    transaction.commit();
}
// endregion
// endregion

// region Menu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_music, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.action_library:
            SwitchView();
            return true;
        case R.id.action_settings:
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}
// endregion