动态加载fragment时需要注意！

fragment.java

// ...
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
	Log.i(TAG, "-- onCreateView(...) --");
	mRootView = (View) inflater.inflate(R.layout.fragment_login, container, false);
	return mRootView;
}

// 当FragmentActivity动态切换Fragment的时候，上面代码片段中的container设置为null或者其后的参数设置为false，
// 否则会报出异常：
// java.lang.IllegalStateException: The specified child already has a
// parent. You must call removeView() on the child's parent first.
// 另外，对fragment进行remove操作前记得进行非空判断

// ...
protected void goHome() {
	FragmentTransaction transaction = getFragmentManager().beginTransaction();

	HomeFragment homeFragment = new HomeFragment();

	if (null == getFragmentManager().findFragmentByTag("tag_home")) {
		transaction.add(R.id.fragment_main, homeFragment, "tag_home");
	}
	
	if (null != getFragmentManager().findFragmentByTag("tag_login")) {
		transaction.remove(getFragmentManager().findFragmentByTag("tag_login"));
	}
	transaction.replace(R.id.fragment_main, homeFragment)
			.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
			.commit();
}