无法将StartFragment解析为类型android错误

Question

我刚刚开始进行android编程，并且仍然在弄清楚片段和活动是如何工作的。所以我正在尝试一些代码，但我收到错误“StartFragment无法解析为类型”

这是我的代码

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;

 public class MainActivity extends FragmentActivity {
    Fragment fragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction transaction = fm.beginTransaction();

        //StartFragment cannot be resolved to a type
        StartFragment myfragment = new StartFragment();

        transaction.add(R.id.namefrag, myfragment);
        transaction.add(R.id.view_fragment,myfragment);
        transaction.add(R.id.load, myfragment);
        transaction.add(R.id.store,myfragment);
    }
}