android - 显示“fragmentManager 无法解析”，通过 Android 4.0 教程 12 工作

Question

除了“fragmentManager”无法解决之外，其他一切都很好，我在这里做错了什么？本教程跳过了本节的某些部分...

@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_activity_frame);
    FragmentManager frgman = getSupportFragmentManager();
    FragmentTransaction frgtrans = frgman.beginTransaction();
    Fragment frag = new Side_Fragment();
    frgtrans.replace(R.id.frag_frame, frag, "SIDE");
    frgtrans.commit();
}

public void swapFrag(View v) {
    FragmentManager fragmentManger = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction =  fragmentManager.beginTransaction();

    Fragment current = fragmentManager.findFragmentByTag("SIDE");

    if(!current.isVisible())
    {
        fragmentTransaction.replace(R.id.frag_frame,  picture, "PIC");
    }
    else
    {
        fragmentTransaction.replace(R.id.frag_frame,  side, "SIDE");            
    }
    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();