在Android4.4中，如果一个class继承自PreferenceActivity。执行startActivity跳转到该类时，会报运行时错误：Caused by: java.lang.RuntimeException: Subclasses of PreferenceActivity must override isValidFragment(String) to verify that the Fragment class is valid!
解决办法时重写isValidFragment方法
@Override
protected boolean isValidFragment(String fragmentName) {
return true;
}