源码：
1 FragmentTransaction mFragmentTranscation = getSupportFragmentManager().beginTransaction(); 2 Fragment mMainFragment = new MainFragment();//此行提示出错 3 mFragmentTranscation.replace(R.id.container, mMainFragment); 4 mFragmentTranscation.commit();
错误提示：无法将MainFragment (Fragment的子类)强制转换成Fragment
解决方法：
在原来的MainFragment中把
import android.app.Fragment;
更改为:
import android.support.v4.app.Fragment;